合并feature1至main遇冲突，git log --merge仅显单个提交的排查

尝试将分支feature1合并到main时出现合并冲突：

$ git status
On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean

$ git merge --no-ff feature1
Auto-merging setup.cfg
CONFLICT (content): Merge conflict in setup.cfg
Automatic merge failed; fix conflicts and then commit the result.

通常git log --merge会显示两个分支中修改冲突文件的提交，但这里只显示了feature1的提交：

$ git log --merge
commit c01a640a5e6c9e4cb8560760aa1878f49534687f (origin/feature1)
[...]

查看setup.cfg确实存在冲突：

<<<<<<< HEAD
    foo==3.45.0
    bar==3.4.2
=======
    foo==3.46.0
    bar==3.6.0
>>>>>>> feature1

git blame显示main中foo==3.45.0来自提交b8d0b8b6（该提交是feature2合并到main的结果），而此前已经将feature2合并到feature1并解决了冲突，且main中涉及该文件的所有提交feature1都已包含。现在需要找出main中导致冲突的提交。

Update 1 #

在main分支执行：

$ git merge-base HEAD feature1
217f35342789e0a6c9b46e7eb4988e61cb6a7ba4

该提交是已合并到main的feature1旧提交，且未修改setup.cfg；设置merge.conflictStyle=diff3后的冲突显示：

<<<<<<< HEAD
    foo==3.45.0
    bar==3.4.2
||||||| merged common ancestors
<<<<<<<<< Temporary merge branch 1
    foo==3.45.0
||||||||| baa2035
    foo==3.41.0
=========
    foo==3.43.0
>>>>>>>>> Temporary merge branch 2
    bar==3.4.2
=======
    foo==3.46.0
    bar==3.6.0
>>>>>>> feature/CD-204-Detect-step-option-typos

Updates 2/3/4 #

分支历史：

git log --oneline --graph --decorate main feature1 feature2 feature3

*   0c85be0 (origin/feature1, feature1) Merge branch 'feature2' into feature1
|\
* | c01a640 [commit from 'feature1']
| | *   3f53bf5 (HEAD -> main, origin/main) Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 217f353 [commit from 'feature1']
| | *   67bee00 Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 70702f7 [commit from 'feature1']
| | *   93c8872 Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 2c80431 [commit from 'feature1']
| | *   323d2a1 Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 8a24b9b [commit from 'feature1']
| | *   19c2462 Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | d8c5679 [commit from 'feature1']
* | | d9ddb8b [commit from 'feature1']
| | *   1951b79 Merge branch 'feature2' into 'main'
| | |\
| | |/
| |/|
| * | b8d0b8b (origin/feature2, feature2) [commit from 'feature2']
| | *   1b4224e Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 96ba75d [commit from 'feature1']
| | *   88f122d Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 27b3e3a [commit from 'feature1']
| | *   5ff415a Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 07faa23 [commit from 'feature1']
| | *   e0d54c5 Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 4b5d664 [commit from 'feature1']
| | *   6098d4d Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 04d9b9e [commit from 'feature1']
| | *   e7586b1 Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 3d967c0 [commit from 'feature1']
* | | 387a3a3 [commit from 'feature1']
| | *   5d7fe99 Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | d5968c6 [commit from 'feature1']
| | *   567b71a Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | | 59b12e0 [commit from 'feature1']
| | *   7f7e3cc Merge branch 'feature1' into 'main'
| | |\
| |_|/
|/| |
* | |   3c403dc Merge remote-tracking branch 'origin/feature3' into feature1
|\ \
* | | | db64cb7 [commit from 'feature1']
| | | *   cef6b50 Merge branch 'feature3' into 'main'
| | | |\
| | |_|/
| |/| |
| * | | de8a647 (origin/feature3) [commit from 'feature3']
| * | | a66b4ce [commit from 'feature3']
| * | | 820f80c [commit from 'feature3']
| * | |   88afa63 Merge branch 'feature2' into feature3
| |\ \
| * | | | cdd90f4 [commit from 'feature3']
|/ / / /
| | | *   2c9c566 Merge branch 'feature2' into 'main'
| | | |\
| | | |/
| | |/|
| | * | f2c5d5c [commit from 'feature2']
| |/ /
| | *   5148816 Merge branch 'feature2' into 'main'
| | |\
| | |/
| |/|
| * | baa2035 [commit from 'feature2']
|/ /

[...]

Update 5 #

各分支setup.cfg相关内容：

• feature1最新提交：

$ git show 0c85be0c96e0b9cde0d03de9ce52ab7496347788:setup.cfg

[...]
    foo==3.46.0
    bar==3.6.0
[...]

• feature2最新提交：

$ git show b8d0b8b6bf1710b3a9d0833e0b613616b44d459c:setup.cfg

[...]
    foo==3.45.0
    bar==3.4.2
[...]

• feature3最新提交：

$ git show de8a64716a6a1f237202dbaf0347f9d077dc2dcb:setup.cfg

[...]
    foo==3.43.0
    bar==3.4.2
[...]

• main最新提交：

$ git show 3f53bf5ceea50b09692bc40d1c1943048f38c735:setup.cfg 

[...]
    foo==3.45.0
    bar==3.4.2
[...]

• 合并基：

$ git merge-base main feature1
217f35342789e0a6c9b46e7eb4988e61cb6a7ba4

$ git show 217f35342789e0a6c9b46e7eb4988e61cb6a7ba4:setup.cfg

[...]
    foo==3.43.0
    bar==3.4.2
[...]

Update 7 #

发现main与feature1存在多个合并基：

# Original repo from my post, not the example from Update 6
$ git checkout main
$ git merge-base --all main feature1

217f35342789e0a6c9b46e7eb4988e61cb6a7ba4
b8d0b8b6bf1710b3a9d0833e0b613616b44d459c

其中b8d0b8b的setup.cfg状态与main一致。

1. 理解多合并基的影响 #

你遇到的是多合并基场景：git merge-base --all返回了两个提交，其中b8d0b8b6是feature2合并到main的提交，而你虽然把feature2合并到了feature1，但Git的合并逻辑在处理多个基时，会用这些基的"联合"状态来对比分支差异。

2. 找出main中导致冲突的提交 #

直接用以下命令，找出main中在合并基之后修改setup.cfg的所有提交：

git log --oneline 217f353..main -- setup.cfg

或者更准确地，针对两个合并基，找出main中不在feature1里的提交：

git log --oneline feature1..main -- setup.cfg

这个命令会列出main分支上有，但feature1分支没有的setup.cfg修改提交，其中就包含导致冲突的b8d0b8b6（feature2合并到main的提交）。

3. 为何git log --merge只显示一个提交？ #

因为git log --merge默认只显示在合并基之后修改冲突文件，且只在其中一个分支存在的提交。而b8d0b8b6对应的修改，你已经通过合并feature2到feature1的操作，让feature1也包含了这个修改的"解决版本"，但Git的合并逻辑认为main中的版本和feature1中的版本仍存在差异，所以冲突产生，但git log --merge没把main侧的提交列出来。

4. 彻底解决冲突的建议 #

既然你已经在feature1中合并过feature2并解决了冲突，现在可以用git rebase把feature1重新基于main最新提交，这样能更清晰地处理冲突：

git checkout feature1
git rebase main

在rebase过程中处理setup.cfg的冲突，完成后再合并到main即可。

内容的提问来源于stack exchange，提问作者Florian Brucker