git 入門教程之衝突合併

若是足夠幸運的話,團隊成員互不影響,彼此相安無事,你們各自基於 master 分支的某個 commit 建立本身的分支,平時在分支上獨立工做,等到一段時間後再合併 merge 到 master 分支,這樣同樣 master 做爲各個功能的集大成者,最終完成項目.

然而事情總不是一路順風的,團隊協做時因爲意見不一樣,遇到衝突簡直是屢見不鮮,既然沒法迴避衝突,當衝突發生時如何應該呢?

背景

基於 master 分支上的某個 commit ,新功能由此繼續開發:

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

新功能分支命名爲 feature ,使用git checkout -b <name> 建立分支並切換:

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

在新功能 feature 分支上開發新功能,並提交:

$ 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(+)
$

不管新功能 feature 是否開發完畢,團隊的其餘成員均有可能處於 master 分支並作相應更改:

$ 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)

其餘成員對新功能有着本身的見解,因而也提交了版本,因爲咱們以前提交的是 git commit c2,而此時master 分支提交的是git commit c3,顯然咱們兩我的的意見不一致!

$ 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(+)
$

正在此時,feature 分支的新功能已開發完畢並主動切換回 master 分支,準備合併 feature
分支.

# 合併 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.
$

因爲項目成員溝通不順暢或者意見不一致,致使了代碼衝突,git 做爲版本控制系統,天然沒法解決這類問題,總不能擅自作主拋棄後來的更改吧或者拋棄分支更改?因此 git
只負責拋出問題,等待咱們程序員去解決問題.

既然是人的問題,那咱們看一下咱們究竟是哪裏不一致,爲何會產生衝突?

# 查看狀態
$ 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")
# 比較差別
$ git diff 
diff --cc test.txt
index 6e00f87,0f95fd7..0000000
--- a/test.txt
+++ b/test.txt
@@@ -3,4 -3,4 +3,8 @@@ see https://snowdreams1006.github.io/gi
  learn git branch
  see https://snowdreams1006.github.io/git/usage/branch-overview.html
  git commit c1
++<<<<<<< HEAD
 +git commit c3
++=======
+ git commit c2
++>>>>>>> feature

和咱們預期同樣,test.txt 文件產生了衝突,當前 HEAD 指向的提交即 master 分支是 git commit c3 ,而 feature 分支是 git commit c2,對於同一個文件的同一行內容發生不一樣的更改,git 不知道也不該該知道如何處理.

# 查看內容
$ cat test.txt
add test.txt
see https://snowdreams1006.github.io/git/usage/remote-repository.html
learn git branch
see https://snowdreams1006.github.io/git/usage/branch-overview.html
git commit c1
<<<<<<< HEAD
git commit c3
=======
git commit c2
>>>>>>> feature

git 用 <<<<<<< 標記一個分支衝突開始,======= 標記分支分割線,>>>>>>> 標記另外一個分支結束.

通過沖突雙方的討論後,彼此間達成妥協,決定修改爲git commit c2 and c3 ,修改後繼續提交:

# 編輯衝突文件,按照協商一致的內容修改文件
$ vim test.txt
# 將衝突內容更改成 git commit c2 and c3
$ cat test.txt
add test.txt
see https://snowdreams1006.github.io/git/usage/remote-repository.html
learn git branch
see https://snowdreams1006.github.io/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

衝突已經解決,如今回顧一下提交歷史,使用git log --graph 圖形化展現提交歷史:

# 查看提交日誌
$ 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://snowdreams1006.github.io/git/usage/branch-overview.html
* 9c30e50248b773e38b032477a859e87abe7c1bb0 learn git branch
* b3d8193bbcb9f76c47e831e3e212f2405ae09f93 (origin/master, origin/HEAD) see https://snowdreams1006.github.io/git/usage/remote-repository.html
* 8e625640348a47ac922409a1ecb4c844385582aa add test.txt
* 9b196aab5bc87eeb11709c9eef35fca283e05c61 Initial commit
$

最後,刪除新功能分支 feature ,不用的分支及時清理乾淨,須要時再建立分支.

$ git branch -d feature

小結

• 沒法杜絕衝突的發生,代碼上的衝突本質上是人爲因素形成的衝突.
• 解決衝突須要有關雙方協商解決,不可能獨自解決衝突,除非你拋棄自我,徹底以對方爲準.
• 使用 git log --graph 命令能夠圖表化查看提交歷史,抑或 git log --pretty=oneline --graph