Merge

$ git log --oneline --graph --all
* c089834 Use temperature 0 for reproducible evals
| * 58a5e60 Ask the judge to quote evidence
| * 5aec6e0 Ask the judge for a rationale
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ git merge-base main feature/rationale
6ae3c51e176b786603aea088486677fe30f409bd
$ git rev-list --left-right --count main...feature/rationale
1	2
$ git log --oneline --left-right main...feature/rationale
< c089834 Use temperature 0 for reproducible evals
> 58a5e60 Ask the judge to quote evidence
> 5aec6e0 Ask the judge for a rationale

# Three dots in git diff: from the merge base to the right-hand side.
$ git diff --stat main...feature/rationale
 prompts/judge.txt | 2 ++
 1 file changed, 2 insertions(+)
# Two dots (or a space): the two tips compared directly.
$ git diff --stat main..feature/rationale
 config/eval.yaml  | 2 +-
 prompts/judge.txt | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

            5aec6e0---58a5e60   feature/rationale
           /
  6ae3c51---c089834             main   (HEAD -> main)
     ^
     merge base of main and feature/rationale

$ git log --oneline --graph --all
* 23db174 Raise batch size to 32
* 6ae3c51 Add eval config, judge prompt and metrics
$ git merge-base --is-ancestor main feature/batch-size
[exit status: 0]
$ git rev-list --count --all
2

$ git merge feature/batch-size
Updating 6ae3c51..23db174
Fast-forward
 config/eval.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
$ git log --oneline --graph --all
* 23db174 Raise batch size to 32
* 6ae3c51 Add eval config, judge prompt and metrics
$ git rev-list --count --all
2
$ git reflog -2
23db174 HEAD@{0}: merge feature/batch-size: Fast-forward
6ae3c51 HEAD@{1}: checkout: moving from feature/batch-size to main
$ cat .git/ORIG_HEAD
6ae3c51e176b786603aea088486677fe30f409bd

  Before                                     After git merge feature/batch-size

  6ae3c51---23db174   feature/batch-size     6ae3c51---23db174   feature/batch-size
     ^                                                    ^
     main  (HEAD -> main)                                 main  (HEAD -> main)

$ git log --oneline --graph --all
* 017bef5 Use temperature 0 for reproducible evals
| * 67feed7 Raise timeout to 60 seconds
|/  
* 23db174 Raise batch size to 32
* 6ae3c51 Add eval config, judge prompt and metrics
$ git merge-base --is-ancestor main feature/timeout
[exit status: 1]
$ git merge-base main feature/timeout
23db1749f261b3f9ca7627a25923389c32a4a64d
$ git rev-list --left-right --count main...feature/timeout
1	1

$ git merge feature/timeout
Auto-merging config/eval.yaml
Merge made by the 'ort' strategy.
 config/eval.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
$ git log --oneline --graph --all
*   6b10077 Merge branch 'feature/timeout'
|\  
| * 67feed7 Raise timeout to 60 seconds
* | 017bef5 Use temperature 0 for reproducible evals
|/  
* 23db174 Raise batch size to 32
* 6ae3c51 Add eval config, judge prompt and metrics
$ git rev-list --count --all
5

$ git cat-file -p HEAD
tree 25ed240b50b6ea31af8a6023d66eac8ce10d5364
parent 017bef5a99c9b0472c2c1fd4181b9d01c243e76c
parent 67feed7ad67adc99e081b8c29515db39c4726dbb
author Lab User <you@example.com> 1788756960 +0530
committer Lab User <you@example.com> 1788756960 +0530

Merge branch 'feature/timeout'
$ git reflog -1
6b10077 HEAD@{0}: merge feature/timeout: Merge made by the 'ort' strategy.
$ cat config/eval.yaml
model: judge-large-v2
temperature: 0.0
max_tokens: 512
batch_size: 32
timeout_s: 60
retries: 2
seed: 7

$ git merge feature/timeout
Already up to date.
$ git merge feature/batch-size
Already up to date.

$ git merge-base main feature/rouge
e650b75915a1645cdb222c495fa22e6273eab187
# base (the merge base, tagged "base" by the demo):
$ git ls-tree -r --abbrev=7 base
100644 blob af7f9b5	README.md
100644 blob c5b3327	config/eval.yaml
100644 blob 9bbcd7a	evalkit/metrics.py
100644 blob cfe0ef0	prompts/judge.txt
100644 blob 3aecde9	requirements.txt
100644 blob 4a41a25	scripts/legacy_eval.sh
# ours (main):
$ git ls-tree -r --abbrev=7 main
100644 blob aa477a1	README.md
100644 blob 0e8b97c	config/eval.yaml
100644 blob 9bbcd7a	evalkit/metrics.py
100644 blob 38cb437	prompts/judge.txt
100644 blob 3aecde9	requirements.txt
100644 blob 4a41a25	scripts/legacy_eval.sh
# theirs (feature/rouge):
$ git ls-tree -r --abbrev=7 feature/rouge
100644 blob af7f9b5	README.md
100644 blob caf8b0d	config/eval.yaml
100644 blob 9bbcd7a	evalkit/metrics.py
100644 blob fe0b96e	evalkit/rouge.py
100644 blob 38cb437	prompts/judge.txt
100644 blob 4a7b8a2	requirements.txt

$ git merge feature/rouge
Auto-merging config/eval.yaml
Merge made by the 'ort' strategy.
 config/eval.yaml       | 2 +-
 evalkit/rouge.py       | 2 ++
 requirements.txt       | 1 +
 scripts/legacy_eval.sh | 2 --
 4 files changed, 4 insertions(+), 3 deletions(-)
 create mode 100644 evalkit/rouge.py
 delete mode 100644 scripts/legacy_eval.sh

# result (the tree of the merge commit):
$ git ls-tree -r --abbrev=7 HEAD
100644 blob aa477a1	README.md
100644 blob cef358f	config/eval.yaml
100644 blob 9bbcd7a	evalkit/metrics.py
100644 blob fe0b96e	evalkit/rouge.py
100644 blob 38cb437	prompts/judge.txt
100644 blob 4a7b8a2	requirements.txt

# What ours changed since the base (HEAD^1 is the first parent of the merge):
$ git diff -U0 base HEAD^1 -- config/eval.yaml
diff --git a/config/eval.yaml b/config/eval.yaml
index c5b3327..0e8b97c 100644
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@ -2 +2 @@ model: judge-large-v2
-temperature: 0.2
+temperature: 0.0
# What theirs changed since the base (HEAD^2 is the second parent):
$ git diff -U0 base HEAD^2 -- config/eval.yaml
diff --git a/config/eval.yaml b/config/eval.yaml
index c5b3327..caf8b0d 100644
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@ -5 +5 @@ batch_size: 16
-timeout_s: 30
+timeout_s: 60
# The merged file carries both changes:
$ git diff -U0 base HEAD -- config/eval.yaml
diff --git a/config/eval.yaml b/config/eval.yaml
index c5b3327..cef358f 100644
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@ -2 +2 @@ model: judge-large-v2
-temperature: 0.2
+temperature: 0.0
@@ -5 +5 @@ batch_size: 16
-timeout_s: 30
+timeout_s: 60

                      67feed7----------.          feature/timeout
                     /                  \
  6ae3c51---23db174---017bef5-----------6b10077   main   (HEAD -> main)
               ^
               merge base

$ git log --oneline --graph --all
*   bd573ed Merge release/1.0 into main, keep temperature 0.0
|\  
| | * 4f30da1 Merge main into release/1.0, keep temperature 0.7
| |/| 
| |/  
|/|   
* | 5d28836 Use temperature 0 for reproducible evals
| * 2725147 Raise temperature for the 1.0 judge
|/  
* 36749ac Add eval config, judge prompt and metrics
$ git merge-base main release/1.0
272514788670fe9d71d00daeca408d3494e15041
$ git merge-base --all main release/1.0
272514788670fe9d71d00daeca408d3494e15041
5d288362f8c011ad12da5920c8cc763443e61c5d

# Merge with only the first candidate as the base:
$ tree=$(git merge-tree --write-tree --merge-base=release/1.0~1 main release/1.0)
$ git show $tree:config/eval.yaml | grep temperature
temperature: 0.0
# Merge with only the second candidate as the base:
$ tree=$(git merge-tree --write-tree --merge-base=main~1 main release/1.0)
$ git show $tree:config/eval.yaml | grep temperature
temperature: 0.7

$ git merge release/1.0
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git ls-files -u
100644 eeb99652ab2e2dc7f9c07b8a0db026159a245750 1	config/eval.yaml
100644 0e8b97cd35b023b2949d7efeed9dbd491d065ae8 2	config/eval.yaml
100644 3e21100524f1361d04738d41f1012b9221082155 3	config/eval.yaml
$ git show :1:config/eval.yaml
model: judge-large-v2
<<<<<<<<< Temporary merge branch 1
temperature: 0.0
=========
temperature: 0.7
>>>>>>>>> Temporary merge branch 2
max_tokens: 512
batch_size: 16
timeout_s: 30
retries: 2
seed: 7

$ git merge --abort
$ git -c merge.conflictStyle=diff3 merge release/1.0
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ cat config/eval.yaml
model: judge-large-v2
<<<<<<< HEAD
temperature: 0.0
||||||| merged common ancestors
<<<<<<<<< Temporary merge branch 1
temperature: 0.0
||||||||| 36749ac
temperature: 0.2
=========
temperature: 0.7
>>>>>>>>> Temporary merge branch 2
=======
temperature: 0.7
>>>>>>> release/1.0
max_tokens: 512
batch_size: 16
timeout_s: 30
retries: 2
seed: 7

  36749ac---5d28836---bd573ed   main   (HEAD -> main)
        \          \ /
         \          X
          \        / \
           2725147---4f30da1    release/1.0

  merge bases of main and release/1.0: 5d28836 and 2725147

Observed behavior : The base version of a conflicted file (git show :1:path, or the middle
                    section in diff3 style) contains conflict markers labelled
                    "Temporary merge branch 1" and "Temporary merge branch 2".
Git state         : git merge-base --all prints two commits; neither is an ancestor of the other.
Mechanism         : The ort strategy first merges the two merge bases with each other. That inner
                    merge conflicts, and its result, markers included, becomes the base.
Root cause        : A criss-cross. Each branch merged the other, and the two merges resolved the
                    same conflict in opposite ways.
Why Git does this : Either base alone would silently reapply one side's old decision, as the
                    two-answer transcript shows. A base that matches neither tip returns the
                    question to a human.
Correct fix       : Resolve it as an ordinary conflict. Read the inner block as the two earlier
                    decisions and the outer sides as the two current values.
Prevention        : Between long-lived branches, merge in one direction only. Keep other
                    branches short enough that they never merge each other.

# ours changed temperature; theirs changed temperature AND seed, and added a prompt line.
$ git diff --stat main...feature/creative-judge
 config/eval.yaml  | 4 ++--
 prompts/judge.txt | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)
$ grep -n -e temperature -e seed config/eval.yaml
2:temperature: 0.0
7:seed: 7

$ git merge -X ours feature/creative-judge
Auto-merging config/eval.yaml
Merge made by the 'ort' strategy.
 config/eval.yaml  | 2 +-
 prompts/judge.txt | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)
$ grep -n -e temperature -e seed config/eval.yaml
2:temperature: 0.0
7:seed: 1234
$ tail -1 prompts/judge.txt
Explain your verdict in one sentence.

$ git merge -X theirs feature/creative-judge
Auto-merging config/eval.yaml
Merge made by the 'ort' strategy.
 config/eval.yaml  | 4 ++--
 prompts/judge.txt | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)
$ grep -n -e temperature -e seed config/eval.yaml
2:temperature: 0.7
7:seed: 1234

$ git merge -s ours feature/creative-judge
Merge made by the 'ours' strategy.
$ grep -n -e temperature -e seed config/eval.yaml
2:temperature: 0.0
7:seed: 7
$ tail -1 prompts/judge.txt
Answer with PASS or FAIL.
# The tree of the merge commit is the tree of its first parent:
$ git rev-parse HEAD^{tree} HEAD^1^{tree}
3dfab55ba26e160c0bf7d8f7533173a3d264618f
3dfab55ba26e160c0bf7d8f7533173a3d264618f
# Yet the history says the branch is merged:
$ git branch --merged
  feature/creative-judge
* main

$ git merge -s theirs feature/creative-judge
Could not find merge strategy 'theirs'.
Available strategies are: octopus ours recursive resolve subtree.
[exit status: 1]

$ git merge -s recursive -X ours feature/creative-judge
Auto-merging config/eval.yaml
Merge made by the 'recursive' strategy.
 config/eval.yaml  | 2 +-
 prompts/judge.txt | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

$ git merge chore/yaml-format
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ cat config/eval.yaml
model: judge-large-v2
metrics:
<<<<<<< HEAD
  - exact_match
  - token_f1
=======
    - exact_match
    - f1
>>>>>>> chore/yaml-format
seed: 7
$ git merge --abort

$ git merge -X ignore-space-change chore/yaml-format
Auto-merging config/eval.yaml
Merge made by the 'ort' strategy.
$ cat config/eval.yaml
model: judge-large-v2
metrics:
  - exact_match
  - token_f1
seed: 7

Observed behavior : After git merge -X ignore-space-change, the formatting branch counts as
                    merged, but the file is not reformatted.
Git state         : The merge commit's tree is identical to its first parent's tree.
Mechanism         : With a whitespace option, "if their version only introduces whitespace
                    changes to a line, our version is used" (git-merge manual).
Root cause        : The option does not merge whitespace changes. It discards them
                    wherever they meet a line that our side kept or changed.
Why Git does this : A line cannot carry their indentation and our text at the same time
                    without Git inventing a third version.
Correct fix       : Run the formatter again on the merge result and commit.
Prevention        : Land formatting-only changes when no other branch is open on those files,
                    or have every branch run the same formatter before merging.

$ cat base.yaml
model: judge-large-v2
temperature: 0.2
max_tokens: 512
batch_size: 16
timeout_s: 30
$ sed 's/temperature: 0.2/temperature: 0.0/' base.yaml > ours.yaml
$ sed 's/timeout_s: 30/timeout_s: 60/' base.yaml > theirs.yaml
$ git merge-file -p ours.yaml base.yaml theirs.yaml
model: judge-large-v2
temperature: 0.0
max_tokens: 512
batch_size: 16
timeout_s: 60
[exit status: 0]

$ sed 's/temperature: 0.2/temperature: 0.7/' base.yaml > theirs.yaml
$ git merge-file -p ours.yaml base.yaml theirs.yaml
model: judge-large-v2
<<<<<<< ours.yaml
temperature: 0.0
=======
temperature: 0.7
>>>>>>> theirs.yaml
max_tokens: 512
batch_size: 16
timeout_s: 30
[exit status: 1]

$ sed 's/temperature: 0.2/temperature: 0.0/' base.yaml > theirs.yaml
$ git merge-file -p ours.yaml base.yaml theirs.yaml
model: judge-large-v2
temperature: 0.0
max_tokens: 512
batch_size: 16
timeout_s: 30
[exit status: 0]

# ours changes line 2, theirs changes line 3: no unchanged line between them.
$ sed 's/max_tokens: 512/max_tokens: 1024/' base.yaml > theirs.yaml
$ git merge-file -p ours.yaml base.yaml theirs.yaml
model: judge-large-v2
<<<<<<< ours.yaml
temperature: 0.0
max_tokens: 512
=======
temperature: 0.2
max_tokens: 1024
>>>>>>> theirs.yaml
batch_size: 16
timeout_s: 30
[exit status: 1]

# ours changes line 2, theirs changes line 4: line 3 is unchanged on both sides.
$ sed 's/batch_size: 16/batch_size: 32/' base.yaml > theirs.yaml
$ git merge-file -p ours.yaml base.yaml theirs.yaml
model: judge-large-v2
temperature: 0.0
max_tokens: 512
batch_size: 32
timeout_s: 30
[exit status: 0]

Observed behavior : A conflict, although the two branches changed different lines.
Git state         : Ours changed line 2 of the file, theirs changed line 3.
Mechanism         : The merge works on hunks. Two hunks with no unchanged line between them
                    form one region, and that region was changed by both sides.
Root cause        : Adjacency. One unchanged line between the edits (the last transcript)
                    is enough to keep them apart.
Why Git does this : It needs a boundary between "independent" and "the same area", and an
                    unchanged line is the only evidence of independence that text offers.
Correct fix       : Take the changed line from each side: temperature 0.0 and max_tokens 1024.
Prevention        : None needed. Recognize the pattern and resolve it in seconds. Do not reach
                    for -X ours, which would drop their line.

  base lines         1    2    3    4    5
  ours changes            #
  theirs changes                         #    far apart: both applied
  theirs changes               #              touches ours: one region, conflict
  theirs changes                    #         one unchanged line between: both applied

$ git log --oneline --graph --all
* 5397d5f Use temperature 0 for reproducible evals
| * 45a7a67 Ask the judge for a rationale
| * 640bfe1 Raise temperature and reseed for judge diversity
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ git merge feature/creative-judge
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]

$ git status
On branch main
You have unmerged paths.
  (fix conflicts and run "git commit")
  (use "git merge --abort" to abort the merge)

Changes to be committed:
	modified:   prompts/judge.txt

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   config/eval.yaml

$ cat config/eval.yaml
model: judge-large-v2
<<<<<<< HEAD
temperature: 0.0
=======
temperature: 0.7
>>>>>>> feature/creative-judge
max_tokens: 512
batch_size: 16
timeout_s: 30
retries: 2
seed: 1234

$ git ls-files -s
100644 c5b33275d88c041381cff59f23d3cd88b9f22c98 1	config/eval.yaml
100644 0e8b97cd35b023b2949d7efeed9dbd491d065ae8 2	config/eval.yaml
100644 db5c556ef5edb6802e492cd59b5a0b9721a882da 3	config/eval.yaml
100644 9bbcd7ae8147833209c2dbce940d2fd9d681c8ac 0	evalkit/metrics.py
100644 38cb43793f7d697e3d7c88c83da85d1fcd783d68 0	prompts/judge.txt
$ git ls-files -u
100644 c5b33275d88c041381cff59f23d3cd88b9f22c98 1	config/eval.yaml
100644 0e8b97cd35b023b2949d7efeed9dbd491d065ae8 2	config/eval.yaml
100644 db5c556ef5edb6802e492cd59b5a0b9721a882da 3	config/eval.yaml

$ git show :1:config/eval.yaml
model: judge-large-v2
temperature: 0.2
max_tokens: 512
batch_size: 16
timeout_s: 30
retries: 2
seed: 7
# What our side did to the base, and what their side did:
$ git diff -U0 :1:config/eval.yaml :2:config/eval.yaml
diff --git a/config/eval.yaml b/config/eval.yaml
index c5b3327..0e8b97c 100644
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@ -2 +2 @@ model: judge-large-v2
-temperature: 0.2
+temperature: 0.0
$ git diff -U0 :1:config/eval.yaml :3:config/eval.yaml
diff --git a/config/eval.yaml b/config/eval.yaml
index c5b3327..db5c556 100644
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@ -2 +2 @@ model: judge-large-v2
-temperature: 0.2
+temperature: 0.7
@@ -7 +7 @@ retries: 2
-seed: 7
+seed: 1234

$ ls .git | grep -E 'MERGE|ORIG_HEAD'
AUTO_MERGE
MERGE_HEAD
MERGE_MODE
MERGE_MSG
ORIG_HEAD
$ cat .git/MERGE_HEAD
45a7a672d9b049a35269a5e7d09e7920fa1d4c87
$ git rev-parse feature/creative-judge
45a7a672d9b049a35269a5e7d09e7920fa1d4c87
$ git rev-parse HEAD ORIG_HEAD
5397d5f953dda5e3acd0d0970078420baf6e0488
5397d5f953dda5e3acd0d0970078420baf6e0488
$ cat .git/MERGE_MSG
Merge branch 'feature/creative-judge'

# Conflicts:
#	config/eval.yaml
$ git cat-file -t AUTO_MERGE
tree

$ git diff
diff --cc config/eval.yaml
index 0e8b97c,db5c556..0000000
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@@ -1,5 -1,5 +1,9 @@@
  model: judge-large-v2
++<<<<<<< HEAD
 +temperature: 0.0
++=======
+ temperature: 0.7
++>>>>>>> feature/creative-judge
  max_tokens: 512
  batch_size: 16
  timeout_s: 30

$ git commit -m "Merge feature/creative-judge"
error: Committing is not possible because you have unmerged files.
hint: Fix them up in the work tree, and then use 'git add/rm <file>'
hint: as appropriate to mark resolution and make a commit.
fatal: Exiting because of an unresolved conflict.
U	config/eval.yaml
[exit status: 128]
$ git switch feature/creative-judge
fatal: cannot switch branch while merging
Consider "git merge --quit" or "git worktree add".
[exit status: 128]

  Working tree                  Index (stage, path, blob)               HEAD -> main -> 5397d5f
  +-------------------------+   +-----------------------------------+   +----------------------+
  | config/eval.yaml        |   | 1  config/eval.yaml    c5b3327    |   | config/eval.yaml     |
  |   merged, except one    |   | 2  config/eval.yaml    0e8b97c    |   |   0e8b97c            |
  |   marker block (line 2) |   | 3  config/eval.yaml    db5c556    |   |                      |
  | prompts/judge.txt       |   | 0  prompts/judge.txt   38cb437    |   | prompts/judge.txt    |
  |   merged                |   | 0  evalkit/metrics.py  9bbcd7a    |   |   cfe0ef0            |
  +-------------------------+   +-----------------------------------+   +----------------------+

  .git/MERGE_HEAD = 45a7a67 (their tip)   .git/ORIG_HEAD = 5397d5f   .git/MERGE_MSG   .git/AUTO_MERGE (a tree)

# The function as both branches found it (the merge base):
$ git show main~1:evalkit/metrics.py | head -2
def exact_match(pred, gold):
    return float(pred == gold)
$ git merge feature/case-insensitive
Auto-merging evalkit/metrics.py
CONFLICT (content): Merge conflict in evalkit/metrics.py
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ head -9 evalkit/metrics.py
def exact_match(pred, gold):
    if pred is None:
        return 0.0
<<<<<<< HEAD
    return float(pred.strip() == gold.strip())
=======
    return float(pred.lower() == gold.lower())
>>>>>>> feature/case-insensitive

$ git checkout --conflict=diff3 evalkit/metrics.py
Recreated 1 merge conflict
$ head -13 evalkit/metrics.py
def exact_match(pred, gold):
<<<<<<< ours
    if pred is None:
        return 0.0
    return float(pred.strip() == gold.strip())
||||||| base
    return float(pred == gold)
=======
    if pred is None:
        return 0.0
    return float(pred.lower() == gold.lower())
>>>>>>> theirs

$ git restore --conflict=zdiff3 evalkit/metrics.py
$ head -11 evalkit/metrics.py
def exact_match(pred, gold):
    if pred is None:
        return 0.0
<<<<<<< ours
    return float(pred.strip() == gold.strip())
||||||| base
    return float(pred == gold)
=======
    return float(pred.lower() == gold.lower())
>>>>>>> theirs

$ git merge --abort
$ git config set merge.conflictStyle zdiff3
$ git config get --show-origin merge.conflictStyle
file:.git/config	zdiff3
$ git merge feature/case-insensitive
Auto-merging evalkit/metrics.py
CONFLICT (content): Merge conflict in evalkit/metrics.py
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ head -11 evalkit/metrics.py
def exact_match(pred, gold):
    if pred is None:
        return 0.0
<<<<<<< HEAD
    return float(pred.strip() == gold.strip())
||||||| 6ae3c51
    return float(pred == gold)
=======
    return float(pred.lower() == gold.lower())
>>>>>>> feature/case-insensitive

  <<<<<<< HEAD                         our version starts      (stage 2)
  ||||||| 6ae3c51                      base version starts     (stage 1; the label is the merge base)
  =======                              their version starts    (stage 3)
  >>>>>>> feature/case-insensitive     end of the block

$ git log --oneline --left-right main...feature/creative-judge
< 5397d5f Use temperature 0 for reproducible evals
> 45a7a67 Ask the judge for a rationale
> 640bfe1 Raise temperature and reseed for judge diversity
$ git log --oneline --left-right --merge
< 5397d5f Use temperature 0 for reproducible evals
> 640bfe1 Raise temperature and reseed for judge diversity

# In your editor: delete the three marker lines and the 0.7 line. Keep temperature 0.0.
$ cat config/eval.yaml
model: judge-large-v2
temperature: 0.0
max_tokens: 512
batch_size: 16
timeout_s: 30
retries: 2
seed: 1234
$ git diff AUTO_MERGE
diff --git a/config/eval.yaml b/config/eval.yaml
index 46bae64..1642b99 100644
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@ -1,9 +1,5 @@
 model: judge-large-v2
-<<<<<<< HEAD
 temperature: 0.0
-=======
-temperature: 0.7
->>>>>>> feature/creative-judge
 max_tokens: 512
 batch_size: 16
 timeout_s: 30

$ git add config/eval.yaml
$ git ls-files -s
100644 1642b99ceb64bd0a58b86f8d20ab8b50fd1c9cee 0	config/eval.yaml
100644 9bbcd7ae8147833209c2dbce940d2fd9d681c8ac 0	evalkit/metrics.py
100644 38cb43793f7d697e3d7c88c83da85d1fcd783d68 0	prompts/judge.txt
$ git status
On branch main
All conflicts fixed but you are still merging.
  (use "git commit" to conclude merge)

Changes to be committed:
	modified:   config/eval.yaml
	modified:   prompts/judge.txt

$ git merge --continue
[main a94e9f6] Merge branch 'feature/creative-judge'
$ git log --oneline --graph
*   a94e9f6 Merge branch 'feature/creative-judge'
|\  
| * 45a7a67 Ask the judge for a rationale
| * 640bfe1 Raise temperature and reseed for judge diversity
* | 5397d5f Use temperature 0 for reproducible evals
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ ls .git | grep -E 'MERGE|ORIG_HEAD'
ORIG_HEAD

$ git show --stat --format=medium HEAD
commit a94e9f6aa320603f006ce6c0414285c7a24e1fb7
Merge: 5397d5f 45a7a67
Author: Lab User <you@example.com>
Date:   Mon Sep 7 10:33:00 2026 +0530

    Merge branch 'feature/creative-judge'
    
    Keep temperature 0.0: reproducible scores are a release requirement.
    The new seed and the rationale line in the judge prompt are taken as they are.

 config/eval.yaml  | 2 +-
 prompts/judge.txt | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

$ git status --short
UU config/eval.yaml
M  prompts/judge.txt
$ grep -n -e '<<<' -e temperature -e '>>>' -e seed config/eval.yaml
2:<<<<<<< HEAD
3:temperature: 0.0
5:temperature: 0.7
6:>>>>>>> feature/creative-judge
11:seed: 1234
$ git restore --ours config/eval.yaml
$ grep -n -e temperature -e seed config/eval.yaml
2:temperature: 0.0
7:seed: 7
$ git status --short
UU config/eval.yaml
M  prompts/judge.txt

$ git restore --theirs config/eval.yaml
$ grep -n -e temperature -e seed config/eval.yaml
2:temperature: 0.7
7:seed: 1234
$ git status --short
UU config/eval.yaml
M  prompts/judge.txt

$ git restore --merge config/eval.yaml
$ grep -n -e '<<<' -e temperature -e '>>>' -e seed config/eval.yaml
2:<<<<<<< ours
3:temperature: 0.0
5:temperature: 0.7
6:>>>>>>> theirs
11:seed: 1234

$ git checkout --ours config/eval.yaml
Updated 1 path from the index
$ git checkout --theirs config/eval.yaml
Updated 1 path from the index
$ git checkout --merge config/eval.yaml
Recreated 1 merge conflict
$ git status --short
UU config/eval.yaml
M  prompts/judge.txt

# Take their whole file, stage it, then change your mind.
$ git restore --theirs config/eval.yaml
$ git add config/eval.yaml
$ git status --short
M  config/eval.yaml
M  prompts/judge.txt
$ git ls-files -s config/eval.yaml
100644 db5c556ef5edb6802e492cd59b5a0b9721a882da 0	config/eval.yaml
$ git restore --merge config/eval.yaml
$ git status --short
UU config/eval.yaml
M  prompts/judge.txt
$ git ls-files -s config/eval.yaml
100644 c5b33275d88c041381cff59f23d3cd88b9f22c98 1	config/eval.yaml
100644 0e8b97cd35b023b2949d7efeed9dbd491d065ae8 2	config/eval.yaml
100644 db5c556ef5edb6802e492cd59b5a0b9721a882da 3	config/eval.yaml

$ git merge feature/creative-judge
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git merge --continue
error: Committing is not possible because you have unmerged files.
hint: Fix them up in the work tree, and then use 'git add/rm <file>'
hint: as appropriate to mark resolution and make a commit.
fatal: Exiting because of an unresolved conflict.
U	config/eval.yaml
[exit status: 128]

$ git merge --abort
$ git status --short --branch
## main
$ ls .git | grep -E 'MERGE|ORIG_HEAD'
ORIG_HEAD
$ git reflog -2
5397d5f HEAD@{0}: reset: moving to HEAD
5397d5f HEAD@{1}: commit: Use temperature 0 for reproducible evals

$ git merge --abort
fatal: There is no merge to abort (MERGE_HEAD missing).
[exit status: 128]
$ git merge --continue
fatal: There is no merge in progress (MERGE_HEAD missing).
[exit status: 128]

$ git merge feature/creative-judge
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git merge --quit
[exit status: 0]
$ ls .git | grep -E 'MERGE|ORIG_HEAD'
ORIG_HEAD
$ git status
On branch main
Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
	modified:   prompts/judge.txt

Unmerged paths:
  (use "git restore --staged <file>..." to unstage)
  (use "git add <file>..." to mark resolution)
	both modified:   config/eval.yaml

# The merge is forgotten, the half-merged files are not. A commit made now has ONE parent:
$ git add config/eval.yaml
$ git commit -q -m "Resolve temperature conflict"
$ git log --oneline --graph --all
* cdacf6e Resolve temperature conflict
* 5397d5f Use temperature 0 for reproducible evals
| * 45a7a67 Ask the judge for a rationale
| * 640bfe1 Raise temperature and reseed for judge diversity
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ git branch --no-merged
  feature/creative-judge

# The clean way back after --quit: reset the index and the files the merge touched.
$ git merge --quit
$ git merge --abort
fatal: There is no merge to abort (MERGE_HEAD missing).
[exit status: 128]
$ git reset --merge
$ git status --short --branch
## main

$ git merge feature/disk-cache
Auto-merging evalkit/cache.py
CONFLICT (add/add): Merge conflict in evalkit/cache.py
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
AA evalkit/cache.py
$ git ls-files -u
100644 7f040298ad3ac9af50f69563114d5f3f5fff3576 2	evalkit/cache.py
100644 8d7d969205f3f1edf8a7f316f04e2481e6df6a31 3	evalkit/cache.py
$ git show :1:evalkit/cache.py
fatal: path 'evalkit/cache.py' is in the index, but not at stage 1
hint: Did you mean ':2:evalkit/cache.py'?
[exit status: 128]

$ cat evalkit/cache.py
<<<<<<< HEAD
_CACHE = {}


def load(key):
    return _CACHE.get(key)
=======
import json


def load(path):
    with open(path) as f:
        return json.load(f)
>>>>>>> feature/disk-cache

$ git merge cleanup/remove-legacy
CONFLICT (modify/delete): scripts/legacy_eval.sh deleted in cleanup/remove-legacy and modified in HEAD.  Version HEAD of scripts/legacy_eval.sh left in tree.
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status
On branch main
You have unmerged paths.
  (fix conflicts and run "git commit")
  (use "git merge --abort" to abort the merge)

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by them: scripts/legacy_eval.sh

no changes added to commit (use "git add" and/or "git commit -a")

$ git status --short
UD scripts/legacy_eval.sh
$ git ls-files -u
100644 4a41a25aa3c40cf94e023b2f4e69974e8d1b0e5f 1	scripts/legacy_eval.sh
100644 26610f62ce9e5b2744199a6dd9e966eb004ca890 2	scripts/legacy_eval.sh
$ ls scripts
legacy_eval.sh

# Stage 3 does not exist for this path. The two commands react differently:
$ git checkout --theirs scripts/legacy_eval.sh
error: path 'scripts/legacy_eval.sh' does not have their version
[exit status: 1]
$ git restore --theirs scripts/legacy_eval.sh
[exit status: 0]
$ test -f scripts/legacy_eval.sh
[exit status: 1]
$ git status --short
UD scripts/legacy_eval.sh
$ git restore --ours scripts/legacy_eval.sh
$ test -f scripts/legacy_eval.sh
[exit status: 0]
$ git restore --merge scripts/legacy_eval.sh
error: path 'scripts/legacy_eval.sh' does not have all necessary versions
[exit status: 1]

$ git merge main
CONFLICT (modify/delete): scripts/legacy_eval.sh deleted in HEAD and modified in main.  Version main of scripts/legacy_eval.sh left in tree.
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
DU scripts/legacy_eval.sh
$ git ls-files -u
100644 4a41a25aa3c40cf94e023b2f4e69974e8d1b0e5f 1	scripts/legacy_eval.sh
100644 26610f62ce9e5b2744199a6dd9e966eb004ca890 3	scripts/legacy_eval.sh
# Decision on this branch: keep the edited file.
$ git add scripts/legacy_eval.sh
$ git status --short
A  scripts/legacy_eval.sh

# Back on main, same conflict as in the first snippet. Decision: the deletion wins.
$ git rm scripts/legacy_eval.sh
rm 'scripts/legacy_eval.sh'
$ git status --short
D  scripts/legacy_eval.sh
$ git merge --continue
[main 7e2950a] Merge branch 'cleanup/remove-legacy'
$ git ls-files
config/eval.yaml
evalkit/metrics.py
prompts/judge.txt

$ git log --oneline --graph --all
* e5b08ff Strip whitespace before comparing
| * 727adba Rename the metrics module to scoring
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ git merge refactor/scoring-module
Merge made by the 'ort' strategy.
 evalkit/{metrics.py => scoring.py} | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 rename evalkit/{metrics.py => scoring.py} (100%)
$ git ls-files evalkit
evalkit/scoring.py
$ head -2 evalkit/scoring.py
def exact_match(pred, gold):
    return float(pred.strip() == gold.strip())

$ git merge refactor/scorers
CONFLICT (rename/rename): evalkit/metrics.py renamed to evalkit/scoring.py in HEAD and to evalkit/scorers.py in refactor/scorers.
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
DD evalkit/metrics.py
UA evalkit/scorers.py
AU evalkit/scoring.py
$ git ls-files -u
100644 9bbcd7ae8147833209c2dbce940d2fd9d681c8ac 1	evalkit/metrics.py
100644 9bbcd7ae8147833209c2dbce940d2fd9d681c8ac 3	evalkit/scorers.py
100644 9bbcd7ae8147833209c2dbce940d2fd9d681c8ac 2	evalkit/scoring.py
$ ls evalkit
scorers.py
scoring.py

# Decision: the module is called scoring. All three paths need an answer.
$ git add evalkit/scoring.py
$ git rm evalkit/scorers.py
rm 'evalkit/scorers.py'
$ git rm evalkit/metrics.py
rm 'evalkit/metrics.py'
$ git status --short
$ git merge --continue
[main 02943f6] Merge branch 'refactor/scorers'
$ git ls-files evalkit
evalkit/scoring.py

$ git merge cleanup/drop-metrics
CONFLICT (rename/delete): evalkit/metrics.py renamed to evalkit/scoring.py in HEAD, but deleted in cleanup/drop-metrics.
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
UD evalkit/scoring.py
$ git ls-files -u
100644 9bbcd7ae8147833209c2dbce940d2fd9d681c8ac 1	evalkit/scoring.py
100644 9bbcd7ae8147833209c2dbce940d2fd9d681c8ac 2	evalkit/scoring.py

$ git diff --summary main...refactor/score-objects
 delete mode 100644 evalkit/metrics.py
 create mode 100644 evalkit/scoring.py
$ git diff --summary --find-renames=30% main...refactor/score-objects
 rename evalkit/{metrics.py => scoring.py} (39%)
$ git merge refactor/score-objects
CONFLICT (modify/delete): evalkit/metrics.py deleted in refactor/score-objects and modified in HEAD.  Version HEAD of evalkit/metrics.py left in tree.
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
UD evalkit/metrics.py
A  evalkit/scoring.py

Observed behavior : CONFLICT (modify/delete) on evalkit/metrics.py, although nobody decided to
                    delete the module. The new evalkit/scoring.py is staged without your edit.
Git state         : Theirs has no metrics.py and a scoring.py that shares 39% of its content.
Mechanism         : Rename detection pairs a deleted path with an added path only when their
                    similarity reaches the threshold, 50% by default. Below that, Git sees a
                    deletion and an addition.
Root cause        : A move and a rewrite in one commit. The snapshot holds no rename, only two
                    paths with different content.
Why Git does this : Trees store names and blob IDs. A rename is an inference from similarity,
                    and every inference needs a cutoff.
Correct fix       : Abort and merge again with -X find-renames=30%, or port your edit into the
                    new file by hand and git rm the old path.
Prevention        : Land the move as its own change and merge it into every open branch before
                    the rewrite starts. Two commits on one branch are not enough for the
                    merge, which compares only the tips, though they keep git log --follow
                    working.

$ git merge --abort
$ git merge -X find-renames=30% refactor/score-objects
Auto-merging evalkit/scoring.py
CONFLICT (content): Merge conflict in evalkit/scoring.py
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
D  evalkit/metrics.py
UU evalkit/scoring.py
$ grep -n -B1 -A5 '<<<<<<<' evalkit/scoring.py
11-def exact_match(pred, gold):
12:<<<<<<< HEAD:evalkit/metrics.py
13-    return float(pred.strip() == gold.strip())
14-=======
15-    return Score("exact_match", float(pred == gold))
16->>>>>>> refactor/score-objects:evalkit/scoring.py
17-

$ git merge feature/new-palette
warning: Cannot merge binary files: reports/confusion.png (HEAD vs. feature/new-palette)
Auto-merging reports/confusion.png
CONFLICT (content): Merge conflict in reports/confusion.png
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
UU reports/confusion.png
$ git ls-files -u
100644 ba14cea3b6767bd483472d2b9ba04134aef2afae 1	reports/confusion.png
100644 32a12ecade27b0c495b09a683cd0c12510e81468 2	reports/confusion.png
100644 c4a999a147a8710d34a4971df06840aaca348ba5 3	reports/confusion.png
$ git diff
diff --cc reports/confusion.png
index 32a12ec,c4a999a..0000000
Binary files differ

# The working tree file is our version (stage 2), byte for byte:
$ git hash-object reports/confusion.png
32a12ecade27b0c495b09a683cd0c12510e81468

# Decision: regenerate later; for now take their file.
$ git restore --theirs reports/confusion.png
$ git hash-object reports/confusion.png
c4a999a147a8710d34a4971df06840aaca348ba5
$ git status --short
UU reports/confusion.png
$ git add reports/confusion.png
$ git status --short
M  reports/confusion.png
$ git merge --continue
[main 4d7fbd3] Merge branch 'feature/new-palette'

$ git merge feature/docs-directory
CONFLICT (file/directory): directory in the way of docs from HEAD; moving it to docs~HEAD instead.
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
D  docs
A  docs/calibration.md
AU docs~HEAD
$ git ls-files -s docs docs~HEAD
100644 37cc29f51e7d512294b921cadd0f36e408ede85a 0	docs/calibration.md
100644 7ef0c38ff113fe6b29f348c4cce89653ba08aac7 2	docs~HEAD

$ git diff --name-status feature/cache...main
R100	evalkit/__init__.py	src/evalkit/__init__.py
R100	evalkit/metrics.py	src/evalkit/metrics.py
R100	evalkit/report.py	src/evalkit/report.py
$ git diff --name-status main...feature/cache
A	evalkit/cache.py
$ git merge feature/cache
CONFLICT (file location): evalkit/cache.py added in feature/cache inside a directory that was renamed in HEAD, suggesting it should perhaps be moved to src/evalkit/cache.py.
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
UA src/evalkit/cache.py
$ git ls-files -u
100644 7f040298ad3ac9af50f69563114d5f3f5fff3576 3	src/evalkit/cache.py
$ ls src/evalkit
__init__.py
cache.py
metrics.py
report.py

# Git has already written the file where it suggests. Accepting the suggestion is one command:
$ git add src/evalkit/cache.py
$ git status --short
A  src/evalkit/cache.py
$ git merge --continue
[main d1b5f4e] Merge branch 'feature/cache'
$ git ls-files src
src/evalkit/__init__.py
src/evalkit/cache.py
src/evalkit/metrics.py
src/evalkit/report.py

# The same merge with merge.directoryRenames=true does not stop:
$ git -c merge.directoryRenames=true merge feature/cache
Path updated: evalkit/cache.py added in feature/cache inside a directory that was renamed in HEAD; moving it to src/evalkit/cache.py.
Merge made by the 'ort' strategy.
 src/evalkit/cache.py | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 src/evalkit/cache.py
# With merge.directoryRenames=false the new file stays in the old directory, without a word:
$ git -c merge.directoryRenames=false merge feature/cache
Merge made by the 'ort' strategy.
 evalkit/cache.py | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 evalkit/cache.py
$ git ls-files evalkit src
evalkit/cache.py
src/evalkit/__init__.py
src/evalkit/metrics.py
src/evalkit/report.py

# main is an ancestor of feature/rationale, so a plain merge would fast-forward.
$ git merge --no-ff feature/rationale
Merge made by the 'ort' strategy.
 prompts/judge.txt | 2 ++
 1 file changed, 2 insertions(+)
$ git log --oneline --graph
*   ec7d2b5 Merge branch 'feature/rationale'
|\  
| * 58a5e60 Ask the judge to quote evidence
| * 5aec6e0 Ask the judge for a rationale
|/  
* 6ae3c51 Add eval config, judge prompt and metrics

$ git merge --no-commit feature/rationale
Updating 6ae3c51..58a5e60
Fast-forward
 prompts/judge.txt | 2 ++
 1 file changed, 2 insertions(+)
$ git log --oneline --graph
* 58a5e60 Ask the judge to quote evidence
* 5aec6e0 Ask the judge for a rationale
* 6ae3c51 Add eval config, judge prompt and metrics

$ git merge --no-ff --no-commit feature/rationale
Automatic merge went well; stopped before committing as requested
$ git status
On branch main
All conflicts fixed but you are still merging.
  (use "git commit" to conclude merge)

Changes to be committed:
	modified:   prompts/judge.txt

$ ls .git | grep -E 'MERGE|ORIG_HEAD'
AUTO_MERGE
MERGE_HEAD
MERGE_MODE
MERGE_MSG
ORIG_HEAD
$ cat .git/MERGE_MODE; echo
no-ff
$ git log --oneline -1
6ae3c51 Add eval config, judge prompt and metrics
$ git merge --abort

$ git log --oneline --graph --all
* d80b525 Use temperature 0 for reproducible evals
| * 58a5e60 Ask the judge to quote evidence
| * 5aec6e0 Ask the judge for a rationale
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ git merge --ff-only feature/rationale
hint: Diverging branches can't be fast-forwarded, you need to either:
hint:
hint: 	git merge --no-ff
hint:
hint: or:
hint:
hint: 	git rebase
hint:
hint: Disable this message with "git config set advice.diverging false"
fatal: Not possible to fast-forward, aborting.
[exit status: 128]
$ git status --short --branch
## main

$ git merge --squash feature/rationale
Automatic merge went well; stopped before committing as requested
Squash commit -- not updating HEAD
$ git status
On branch main
Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
	modified:   prompts/judge.txt

$ ls .git | grep -E 'MERGE|ORIG_HEAD|SQUASH'
AUTO_MERGE
ORIG_HEAD
SQUASH_MSG
$ head -3 .git/SQUASH_MSG
Squashed commit of the following:

commit 58a5e6004856ba05b88a2920c3684d15859a867b

$ git commit -q -m "Ask the judge for a rationale and for evidence"
$ git log --oneline --graph --all
* 4b0b1d4 Ask the judge for a rationale and for evidence
* d80b525 Use temperature 0 for reproducible evals
| * 58a5e60 Ask the judge to quote evidence
| * 5aec6e0 Ask the judge for a rationale
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ git show -s --format="%h parents: %p" HEAD
4b0b1d4 parents: d80b525
$ git branch --no-merged
  feature/rationale
$ git branch -d feature/rationale
error: the branch 'feature/rationale' is not fully merged
hint: If you are sure you want to delete it, run 'git branch -D feature/rationale'
hint: Disable this message with "git config set advice.forceDeleteBranch false"
[exit status: 1]

# The squash commit recorded no second parent, so the merge base has not moved:
$ git log --oneline -1 $(git merge-base main feature/rationale)
6ae3c51 Add eval config, judge prompt and metrics
$ git merge --squash feature/rationale
Auto-merging prompts/judge.txt
CONFLICT (content): Merge conflict in prompts/judge.txt
Squash commit -- not updating HEAD
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ cat prompts/judge.txt
You are a strict grader.
Answer with PASS or FAIL.
<<<<<<< HEAD
Explain your verdict in one sentence.
=======
Explain your verdict in two sentences.
>>>>>>> feature/rationale
Quote the evidence you used.

Observed behavior : Squashing the same branch into main a second time conflicts on a line that
                    the first squash had already delivered.
Git state         : git merge-base main feature/rationale is still 6ae3c51, the original fork.
Mechanism         : The first squash commit has one parent, so no commit of the branch became an
                    ancestor of main. The second merge compares both tips with the old base
                    again: main "changed" the line (through the squash) and so did the branch.
Root cause        : Content was merged without ancestry, so the merge base never moved.
Why Git does this : The merge base is computed from parent links, and a squash writes none.
Correct fix       : Resolve the conflict in favour of the newer text. Then stop reusing the
                    branch.
Prevention        : One squash per branch: delete the branch afterwards and start the next one
                    from main. For branches that must live on, use real merge commits.

  git merge --no-ff feature           git merge --squash feature, then git commit

  A-----------M   main                A---S       main      S has one parent
   \         /                         \
    B-------C     feature               B---C     feature   still listed as not merged

  M and S record the same tree. Only M records where it came from.

# docs/readme is one commit ahead of main. merge.ff=false behaves like --no-ff:
$ git -c merge.ff=false merge docs/readme
Merge made by the 'ort' strategy.
 README.md | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 README.md
# merge.ff=only behaves like --ff-only:
$ git -c merge.ff=only -c advice.diverging=false merge feature/rationale
fatal: Not possible to fast-forward, aborting.
[exit status: 128]

$ git log --oneline --graph
* 630eac8 Raise batch size to 32
*   821b8ff Merge branch 'feature/rationale'
|\  
| * 58a5e60 Ask the judge to quote evidence
| * 5aec6e0 Ask the judge for a rationale
* | c089834 Use temperature 0 for reproducible evals
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ git cat-file -p 821b8ff
tree 3e976d90175716430f0495d15e71b1a0069e93e1
parent c089834537b955876054c69c0f4bfbe6230b0cb2
parent 58a5e6004856ba05b88a2920c3684d15859a867b
author Lab User <you@example.com> 1788756120 +0530
committer Lab User <you@example.com> 1788756120 +0530

Merge branch 'feature/rationale'

$ git rev-parse --short 821b8ff^1
c089834
$ git rev-parse --short 821b8ff^2
58a5e60
# The commits that came in through the merge: reachable from parent 2, not from parent 1.
$ git log --oneline 821b8ff^1..821b8ff^2
58a5e60 Ask the judge to quote evidence
5aec6e0 Ask the judge for a rationale
# The same range plus the merge itself, with the ^- shorthand:
$ git log --oneline 821b8ff^-
821b8ff Merge branch 'feature/rationale'
58a5e60 Ask the judge to quote evidence
5aec6e0 Ask the judge for a rationale

$ git log --oneline --first-parent
630eac8 Raise batch size to 32
821b8ff Merge branch 'feature/rationale'
c089834 Use temperature 0 for reproducible evals
6ae3c51 Add eval config, judge prompt and metrics
$ git log --oneline --merges
821b8ff Merge branch 'feature/rationale'
$ git log --oneline --no-merges
630eac8 Raise batch size to 32
c089834 Use temperature 0 for reproducible evals
58a5e60 Ask the judge to quote evidence
5aec6e0 Ask the judge for a rationale
6ae3c51 Add eval config, judge prompt and metrics

# What main gained from the merge:
$ git diff --stat 821b8ff^1 821b8ff
 prompts/judge.txt | 2 ++
 1 file changed, 2 insertions(+)
# What the feature branch would have gained from it:
$ git diff --stat 821b8ff^2 821b8ff
 config/eval.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

            5aec6e0---58a5e60             feature/rationale
           /                 \
  6ae3c51---c089834-----------821b8ff---630eac8   main   (HEAD -> main)

  821b8ff^1 = c089834   where main was when the merge was made
  821b8ff^2 = 58a5e60   what was merged
  git log --first-parent main:   630eac8, 821b8ff, c089834, 6ae3c51

$ git log --oneline --first-parent -3 main
cfc99c8 Retry the judge three times
630eac8 Raise batch size to 32
821b8ff Merge branch 'feature/rationale'
$ git switch -q feature/httpx
$ git merge main
Merge made by the 'ort' strategy.
 config/eval.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
$ git switch -q main
$ git merge feature/httpx
Updating cfc99c8..3f3fd07
Fast-forward
 requirements.txt | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 requirements.txt
$ git log --oneline --graph -4
*   3f3fd07 Merge branch 'main' into feature/httpx
|\  
| * cfc99c8 Retry the judge three times
* | 042925e Add httpx for the judge client
|/  
* 630eac8 Raise batch size to 32
$ git log --oneline --first-parent -3 main
3f3fd07 Merge branch 'main' into feature/httpx
042925e Add httpx for the judge client
630eac8 Raise batch size to 32

$ git merge topic/prompt topic/deps topic/docs
Trying simple merge with topic/prompt
Trying simple merge with topic/deps
Trying simple merge with topic/docs
Merge made by the 'octopus' strategy.
 README.md         | 2 ++
 prompts/judge.txt | 1 +
 requirements.txt  | 1 +
 3 files changed, 4 insertions(+)

$ git log --oneline --graph
*---.   6cd1b13 Merge branches 'topic/prompt', 'topic/deps' and 'topic/docs'
|\ \ \  
| | | * 436e24c Document how to run
| | * | 6e9e321 Add httpx for the judge client
| | |/  
| * / f18e761 Ask the judge for a rationale
| |/  
* / 5ab7b4d Use temperature 0 for reproducible evals
|/  
* adad948 Add README and requirements
* 6ae3c51 Add eval config, judge prompt and metrics
$ git cat-file -p HEAD
tree 25553fcdd3840e13707bf49acc52fbfc81ef0fba
parent 5ab7b4d031080365343d89dcd529d514e9f9b01c
parent f18e7614e71850ee7b09c35e79b2e1a668d5f925
parent 6e9e3211e05899f0aa9598b4d578584f9189d724
parent 436e24c23d49f55d3231c8e61c555e6945411e92
author Lab User <you@example.com> 1788756420 +0530
committer Lab User <you@example.com> 1788756420 +0530

Merge branches 'topic/prompt', 'topic/deps' and 'topic/docs'
$ git reflog -1
6cd1b13 HEAD@{0}: merge topic/prompt topic/deps topic/docs: Merge made by the 'octopus' strategy.

# topic/temperature changes the same line as main.
$ git merge topic/prompt topic/temperature topic/docs
Trying simple merge with topic/prompt
Trying simple merge with topic/temperature
Simple merge did not work, trying automatic merge.
Auto-merging config/eval.yaml
ERROR: content conflict in config/eval.yaml
fatal: merge program failed
Automated merge did not work.
Should not be doing an octopus.
Merge with strategy octopus failed.
[exit status: 2]
$ git status --short --branch
## main
$ ls .git | grep -E 'MERGE|ORIG_HEAD'
ORIG_HEAD

$ git log --oneline --graph --all
* 5008877 Add a leaderboard ranked by accuracy
| * d1c3cff Rename accuracy() to mean_score()
|/  
* 68c652c Add the report module and the import check
* 6ae3c51 Add eval config, judge prompt and metrics
$ git merge -q refactor/mean-score
$ git merge feature/leaderboard
Merge made by the 'ort' strategy.
 evalkit/leaderboard.py | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 evalkit/leaderboard.py

$ sh ci/check_imports.sh
FAIL evalkit/leaderboard.py imports accuracy, which evalkit/metrics.py does not define
[exit status: 1]

# The same check on each parent of the merge commit:
$ git switch -q --detach main^1 && sh ci/check_imports.sh
OK every import from evalkit.metrics resolves
$ git switch -q --detach main^2 && sh ci/check_imports.sh
OK every import from evalkit.metrics resolves
$ git switch -q main

# Paths each side changed since the merge base:
$ git diff --name-only main^2...main^1
evalkit/metrics.py
evalkit/report.py
$ git diff --name-only main^1...main^2
evalkit/leaderboard.py

Observed behavior : Two green branches, a merge without conflict, a red merge commit.
Git state         : The sides changed disjoint paths: metrics.py and report.py on one,
                    leaderboard.py on the other.
Mechanism         : By the rule table, a path changed on one side only is taken as it is.
                    No file-level merge ran. There was nothing for Git to compare.
Root cause        : The dependency between the two changes, a renamed function and a new
                    caller of the old name, lives in the Python import system, not in the
                    text of any one file.
Why Git does this : Git merges snapshots of text. It has no parser, no type checker and no
                    test runner, for any language.
Correct fix       : Update the caller, in a commit on top of the merge (below) or inside the
                    merge commit (see "Evil merges").
Prevention        : Test the merge result before it reaches main: CI on the pull request's
                    merge commit, plus a rule that the branch is up to date with main, or a
                    merge queue (Chapter 18).

# The repair is a normal, reviewable commit on top of the merge.
$ git diff --stat
 evalkit/leaderboard.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
$ git commit -q -a -m "Use mean_score() in the leaderboard"
$ sh ci/check_imports.sh
OK every import from evalkit.metrics resolves

$ git log --oneline --graph --all
* a2a0277 Revert "Allow long answers: max_tokens 2048"
* 523ed40 Allow long answers: max_tokens 2048
| * 4fac9ee Ask for full sentences
| * c8e320d Allow long answers: max_tokens 2048
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ grep max_tokens config/eval.yaml
max_tokens: 512

$ git merge feature/long-answers
Merge made by the 'ort' strategy.
 config/eval.yaml  | 2 +-
 prompts/judge.txt | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)
$ grep max_tokens config/eval.yaml
max_tokens: 2048

# base, ours, theirs, result:
$ git show $(git merge-base HEAD^1 HEAD^2):config/eval.yaml | grep max_tokens
max_tokens: 512
$ git show HEAD^1:config/eval.yaml | grep max_tokens
max_tokens: 512
$ git show HEAD^2:config/eval.yaml | grep max_tokens
max_tokens: 2048
$ git show HEAD:config/eval.yaml | grep max_tokens
max_tokens: 2048

$ git log --oneline --first-parent -5
9a6385a Merge branch 'topic/max-tokens'
fc83756 Merge branch 'topic/docs'
8353ff1 Add requirements
70bae5f Merge branch 'feature/creative-judge'
5397d5f Use temperature 0 for reproducible evals
# By default git log shows no diff for a merge commit, with -p or with --stat:
$ git log -1 -p --format='%h %s' fc83756
fc83756 Merge branch 'topic/docs'
$ git log -1 --stat --format='%h %s' fc83756
fc83756 Merge branch 'topic/docs'

# git show uses the dense combined format (--cc) for merges.
$ git show --format='%h %s' 70bae5f
70bae5f Merge branch 'feature/creative-judge'

$ git show --format='%h %s' fc83756
fc83756 Merge branch 'topic/docs'

diff --cc config/eval.yaml
index 1642b99,1642b99..29fd375
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@@ -3,5 -3,5 +3,5 @@@ temperature: 0.
  max_tokens: 512
  batch_size: 16
  timeout_s: 30
--retries: 2
++retries: 0
  seed: 1234

$ git log --merges --remerge-diff --format='== %h %s'
== 9a6385a Merge branch 'topic/max-tokens'
== fc83756 Merge branch 'topic/docs'

diff --git a/config/eval.yaml b/config/eval.yaml
index 1642b99..29fd375 100644
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@ -3,5 +3,5 @@ temperature: 0.0
 max_tokens: 512
 batch_size: 16
 timeout_s: 30
-retries: 2
+retries: 0
 seed: 1234
== 70bae5f Merge branch 'feature/creative-judge'

diff --git a/config/eval.yaml b/config/eval.yaml
remerge CONFLICT (content): Merge conflict in config/eval.yaml
index 2c6727a..1642b99 100644
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@ -1,9 +1,5 @@
 model: judge-large-v2
-<<<<<<< 5397d5f (Use temperature 0 for reproducible evals)
 temperature: 0.0
-=======
-temperature: 0.7
->>>>>>> 45a7a67 (Ask the judge for a rationale)
 max_tokens: 512
 batch_size: 16
 timeout_s: 30

# Everything a merge brought to main, as one ordinary diff against its first parent:
$ git show --first-parent --format='%h %s' fc83756
fc83756 Merge branch 'topic/docs'

diff --git a/README.md b/README.md
new file mode 100644
index 0000000..e8fdfb1
--- /dev/null
+++ b/README.md
@@ -0,0 +1 @@
+# evalkit
diff --git a/config/eval.yaml b/config/eval.yaml
index 1642b99..29fd375 100644
--- a/config/eval.yaml
+++ b/config/eval.yaml
@@ -3,5 +3,5 @@ temperature: 0.0
 max_tokens: 512
 batch_size: 16
 timeout_s: 30
-retries: 2
+retries: 0
 seed: 1234

$ git clone -q --bare evalkit server.git
$ cd server.git
$ git rev-parse --is-bare-repository
true
$ git log --oneline --graph --all
* 7c974a2 Add a README
| * 5397d5f Use temperature 0 for reproducible evals
|/  
| * 45a7a67 Ask the judge for a rationale
| * 640bfe1 Raise temperature and reseed for judge diversity
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ git merge docs/readme
fatal: this operation must be run in a work tree
[exit status: 128]

$ git merge-tree --write-tree main docs/readme
0c05f61e275e97d119913a164e7312d48cd50d66
[exit status: 0]
$ tree=$(git merge-tree --write-tree main docs/readme)
$ git ls-tree -r --abbrev=7 $tree
100644 blob af7f9b5	README.md
100644 blob 0e8b97c	config/eval.yaml
100644 blob 9bbcd7a	evalkit/metrics.py
100644 blob cfe0ef0	prompts/judge.txt

$ commit=$(git commit-tree $tree -p main -p docs/readme -m "Merge branch 'docs/readme'")
$ git update-ref refs/heads/main $commit
$ git log --oneline --graph -4 main
*   40fb5aa Merge branch 'docs/readme'
|\  
| * 7c974a2 Add a README
* | 5397d5f Use temperature 0 for reproducible evals
|/  
* 6ae3c51 Add eval config, judge prompt and metrics

$ git merge-tree --write-tree main feature/creative-judge
9615415b8675a4fb67a61eb8a37e816decd78066
100644 c5b33275d88c041381cff59f23d3cd88b9f22c98 1	config/eval.yaml
100644 0e8b97cd35b023b2949d7efeed9dbd491d065ae8 2	config/eval.yaml
100644 db5c556ef5edb6802e492cd59b5a0b9721a882da 3	config/eval.yaml

Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
[exit status: 1]

$ tree=$(git merge-tree --write-tree main feature/creative-judge | head -1)
$ git show $tree:config/eval.yaml | head -6
model: judge-large-v2
<<<<<<< main
temperature: 0.0
=======
temperature: 0.7
>>>>>>> feature/creative-judge

# A yes/no answer for a "can this be merged?" indicator:
$ git merge-tree --quiet main feature/creative-judge
[exit status: 1]
$ git merge-tree --write-tree --name-only --no-messages main feature/creative-judge
9615415b8675a4fb67a61eb8a37e816decd78066
config/eval.yaml
[exit status: 1]

$ git log --oneline --graph
*   821b8ff Merge branch 'feature/rationale'
|\  
| * 58a5e60 Ask the judge to quote evidence
| * 5aec6e0 Ask the judge for a rationale
* | c089834 Use temperature 0 for reproducible evals
|/  
* 6ae3c51 Add eval config, judge prompt and metrics
$ git revert --no-edit HEAD
error: commit 821b8ff2e4e35c648578cd9e11514117ae0fd1b9 is a merge but no -m option was given.
fatal: revert failed
[exit status: 128]
$ git revert --no-edit -m 1 HEAD
[main 504ae98] Revert "Merge branch 'feature/rationale'"
 Date: Mon Sep 7 10:15:00 2026 +0530
 1 file changed, 2 deletions(-)
$ cat prompts/judge.txt
You are a strict grader.
Answer with PASS or FAIL.

$ git log --oneline main..feature/rationale
b752dc4 Give the judge 60 seconds for longer answers
$ git merge feature/rationale
Auto-merging config/eval.yaml
Merge made by the 'ort' strategy.
 config/eval.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
# The timeout arrived. The two prompt lines of the first merge did not come back:
$ grep timeout_s config/eval.yaml
timeout_s: 60
$ cat prompts/judge.txt
You are a strict grader.
Answer with PASS or FAIL.
$ git branch --merged
  feature/rationale
* main

# A staged change in a file the merge does not even touch:
$ echo "# scoring helpers" >> evalkit/metrics.py
$ git add evalkit/metrics.py
$ git merge feature/creative-judge
error: Your local changes to the following files would be overwritten by merge:
  evalkit/metrics.py
Merge with strategy ort failed.
[exit status: 2]

# The branch adds NOTES.md. You have an untracked file with the same name:
$ echo "my scratch notes" > NOTES.md
$ git merge feature/creative-judge
error: The following untracked working tree files would be overwritten by merge:
	NOTES.md
Please move or remove them before you merge.
Aborting
Merge with strategy ort failed.
[exit status: 2]

# An uncommitted edit in a file the merge does not touch survives merge and abort.
$ echo "# evalkit" > NOTES.md
$ git merge feature/creative-judge
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
UU config/eval.yaml
M  prompts/judge.txt
?? NOTES.md
$ git merge --abort
$ git status --short
?? NOTES.md

# An uncommitted edit in a file the merge DOES touch stops the merge before it starts...
$ echo "Be concise." >> prompts/judge.txt
$ git merge feature/creative-judge
error: Your local changes to the following files would be overwritten by merge:
	prompts/judge.txt
Please commit your changes or stash them before you merge.
Aborting
Merge with strategy ort failed.
[exit status: 2]
# ...unless Git stashes it for you.
$ git merge --autostash feature/creative-judge
Created autostash: 02ed132
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
When finished, apply stashed changes with `git stash pop`
[exit status: 1]
$ ls .git | grep -E 'MERGE|ORIG_HEAD'
AUTO_MERGE
MERGE_AUTOSTASH
MERGE_HEAD
MERGE_MODE
MERGE_MSG
ORIG_HEAD
$ git merge --abort
Applied autostash.
$ git status --short
 M prompts/judge.txt

# An uncommitted edit in a file that the merge also changes (on another line):
$ sed -e 's/strict grader/strict but fair grader/' prompts/judge.txt > j && mv j prompts/judge.txt
$ git status --short
 M prompts/judge.txt
$ git merge --autostash feature/creative-judge
Created autostash: 1b5e0ea
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
When finished, apply stashed changes with `git stash pop`
[exit status: 1]
$ git status --short
UU config/eval.yaml
M  prompts/judge.txt
# The hint says "git stash pop". The stash list is empty:
$ git stash list
$ git stash pop
No stash entries found.
[exit status: 1]
$ git log -1 --format="%h %s" MERGE_AUTOSTASH
1b5e0ea On main: autostash

# Resolve the conflict as in section 8.10, then conclude the merge:
$ git add config/eval.yaml
$ git merge --continue
[main 29f236b] Merge branch 'feature/creative-judge'
Applied autostash.
$ git status --short
 M prompts/judge.txt
$ cat prompts/judge.txt
You are a strict but fair grader.
Answer with PASS or FAIL.
Explain your verdict in one sentence.
$ git stash list

$ git merge feature/creative-judge
Auto-merging config/eval.yaml
CONFLICT (content): Merge conflict in config/eval.yaml
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
# Nothing was edited. git add accepts the file anyway:
$ git add config/eval.yaml
$ git status --short
M  config/eval.yaml
M  prompts/judge.txt
$ git diff --cached --check
config/eval.yaml:2: leftover conflict marker
config/eval.yaml:4: leftover conflict marker
config/eval.yaml:6: leftover conflict marker
[exit status: 2]

$ git merge feature/creative-judge
fatal: You have not concluded your merge (MERGE_HEAD exists).
Please, commit your changes before you merge.
[exit status: 128]
$ git commit -m "Resolve config" config/eval.yaml
fatal: cannot do a partial commit during a merge.
[exit status: 128]

$ git merge-base main imported/prompt-library
[exit status: 1]
$ git merge imported/prompt-library
fatal: refusing to merge unrelated histories
[exit status: 128]

# v0.1 is an annotated tag, one commit ahead of main, stored as refs/tags/v0.1:
$ git cat-file -t v0.1
tag
$ git merge v0.1
Updating 5397d5f..2f528c3
Fast-forward
 README.md | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 README.md

$ git merge-base --all main release/1.0
f66460bde7a1c01671e6268b8f4209a580951592
5397d5f953dda5e3acd0d0970078420baf6e0488
$ git merge -s resolve release/1.0
Trying simple merge.
Simple merge failed, trying Automatic merge.
Added config/eval.yaml in both, but differently.
fatal: unable to read blob object e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
error: Could not stat : No such file or directory
ERROR: content conflict in config/eval.yaml
fatal: merge program failed
Automatic merge failed; fix conflicts and then commit the result.
[exit status: 1]
$ git status --short
AA config/eval.yaml
$ git ls-files -u
100644 0e8b97cd35b023b2949d7efeed9dbd491d065ae8 2	config/eval.yaml
100644 3e21100524f1361d04738d41f1012b9221082155 3	config/eval.yaml
# The path is unmerged, and the file contains no conflict marker:
$ grep -n -e "<<<<<<<" -e temperature -e ">>>>>>>" config/eval.yaml
2:temperature: 0.0
$ git merge --abort

# The strategies that exist as separate programs (ort is built into git merge itself):
$ ls "$(git --exec-path)" | grep -E "^git-merge-(octopus|ours|recursive|resolve|subtree)$"
git-merge-octopus
git-merge-ours
git-merge-recursive
git-merge-resolve
git-merge-subtree
$ head -6 "$(git --exec-path)/git-merge-resolve"
#!/bin/sh
#
# Copyright (c) 2005 Linus Torvalds
# Copyright (c) 2005 Junio C Hamano
#
# Resolve two trees, using enhanced multi-base read-tree.