冲突合并

如果足够幸运的话,团队成员互不影响,彼此相安无事,大家各自基于 master 分支的某个 commit 创建自己的分支,平时在分支上独立工作,等到一段时间后再合并 merge 到 master 分支,这样一样 master 作为各个功能的集大成者,最终完成项目.

然而事情总不是一帆风顺的,团队协作时由于意见不同,遇到冲突简直是家常便饭,既然无法回避冲突,当冲突发生时如何应该呢?

背景

基于 master 分支上的某个 commit ,新功能由此继续开发:

echo "git commit c1" >> test.txt
$ git add test.txt
$ git commit -m "git commit c1"

git-commit-c1.png

新功能分支命名为 feature ,使用git checkout -b <name> 创建分支并切换:

$git checkout -b feature
Switched to a new branch 'feature'
$ 

git-checkout-feature.png

在新功能 feature 分支上开发新功能,并提交:

$ echo "git commit c2" >> test.txt
$ git add test.txt
$ git commit -m "git commit c2"
[feature 0fe95f8] git commit c2
 1 file changed, 1 insertion(+)
$ 

git-commit-c2.png

无论新功能 feature 是否开发完毕,团队的其他成员均有可能处于 master 分支并做相应更改:

$ git checkout master
Switched to branch 'master'
Your branch is ahead of 'origin/master' by 3 commits.
  (use "git push" to publish your local commits)

git-checkout-master-c1.png

其他成员对新功能有着自己的看法,于是也提交了版本,由于我们之前提交的是 git commit c2,而此时master 分支提交的是git commit c3,显然我们两个人的意见不一致!

$ echo "git commit c3" >> test.txt
$ git add test.txt
$ git commit -m "git commit c3"
[master 0949cc3] git commit c3
 1 file changed, 1 insertion(+)
$ 

git-commit-c3.png

正在此时,feature 分支的新功能已开发完毕并主动切换回 master 分支,准备合并 feature 分支.

# 合并 feature 分支
$ git merge feature
Auto-merging test.txt
CONFLICT (content): Merge conflict in test.txt
Automatic merge failed; fix conflicts and then commit the result.
$

由于项目成员沟通不畅或者意见不一致,导致了代码冲突,git 作为版本控制系统,自然无法解决这类问题,总不能擅自做主抛弃后来的更改吧或者抛弃分支更改?所以 git 只负责抛出问题,等待我们程序员去解决问题.

既然是人的问题,那我们看一下我们到底是哪里不一致,为什么会产生冲突?

# 查看状态
$ git status
On branch master
Your branch is ahead of 'origin/master' by 4 commits.
  (use "git push" to publish your local commits)

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

Unmerged paths:
  (use "git add <file>..." to mark resolution)

    both modified:   test.txt

no changes added to commit (use "git add" and/or "git commit -a")
# 比较差异
$ git diff 
diff --cc test.txt
index 6e00f87,0f95fd7..0000000
--- a/test.txt
+++ b/test.txt
@@@ -3,4 -3,4 +3,8 @@@ see https://gitbook.prlrr.com/gi
  learn git branch
  see https://gitbook.prlrr.com/git/usage/branch-overview.html
  git commit c1
++<<<<<<< HEAD
 +git commit c3
++=======
+ git commit c2
++>>>>>>> feature

和我们预期一样,test.txt 文件产生了冲突,当前 HEAD 指向的提交即 master 分支是 git commit c3 ,而 feature 分支是 git commit c2,对于同一个文件的同一行内容发生不同的更改,git 不知道也不应该知道如何处理.

# 查看内容
$ cat test.txt
add test.txt
see https://gitbook.prlrr.com/git/usage/remote-repository.html
learn git branch
see https://gitbook.prlrr.com/git/usage/branch-overview.html
git commit c1
<<<<<<< HEAD
git commit c3
=======
git commit c2
>>>>>>> feature

git 用 <<<<<<< 标记一个分支冲突开始,======= 标记分支分割线,>>>>>>> 标记另一个分支结束.

经过冲突双方的讨论后,彼此间达成妥协,决定修改成git commit c2 and c3 ,修改后继续提交:

# 编辑冲突文件,按照协商一致的内容修改文件
$ vim test.txt
# 将冲突内容更改为 git commit c2 and c3
$ cat test.txt
add test.txt
see https://gitbook.prlrr.com/git/usage/remote-repository.html
learn git branch
see https://gitbook.prlrr.com/git/usage/branch-overview.html
git commit c1
git commit c2 and c3
$ git add test.txt
$ git commit -m "fix conflict"
[master 3b8f434] fix conflict

冲突已经解决,现在回顾一下提交历史,使用git log --graph 图形化展示提交历史:

# 查看提交日志
$ git log --pretty=oneline --graph
*   3b8f434013caa8c27fade4c59d7aa2ee2c079636 (HEAD -> master) fix conflict
|\  
| * 0fe95f871b371834d30ea17faa82f84b7d67672b (feature) git commit c2
* | 0949cc319e099d554795d03c69ee38923af00d6c git commit c3
|/  
* 5c482cd9965b9dfd4f273b43b240ed7db66167a8 git commit c1
* 413a4d1d2aab5ab85b6097d4b9f81cb5601c3b26 see https://gitbook.prlrr.com/git/usage/branch-overview.html
* 9c30e50248b773e38b032477a859e87abe7c1bb0 learn git branch
* b3d8193bbcb9f76c47e831e3e212f2405ae09f93 (origin/master, origin/HEAD) see https://gitbook.prlrr.com/git/usage/remote-repository.html
* 8e625640348a47ac922409a1ecb4c844385582aa add test.txt
* 9b196aab5bc87eeb11709c9eef35fca283e05c61 Initial commit
$ 

git-merge-with-conflict.png

最后,删除新功能分支 feature ,不用的分支及时清理干净,需要时再创建分支.

$ git branch -d feature

小结

• 无法杜绝冲突的发生,代码上的冲突本质上是人为因素造成的冲突.

• 解决冲突需要有关双方协商解决,不可能独自解决冲突,除非你抛弃自我,完全以对方为准.

• 使用 git log --graph 命令可以图表化查看提交历史,抑或 git log --pretty=oneline --graph