Git解決沖突

人生不如意之事十之八九，合并分支往往也不是一帆風順的。

準備新的feature1分支，繼續我們的新分支開發：

$ git switch -c feature1
Switched to a new branch 'feature1'

修改readme.txt最后一行，改為：

Creating a new branch is quick AND simple.

在feature1分支上提交：

$ git add readme.txt

$ git commit -m "AND simple"
[feature1 14096d0] AND simple
 1 file changed, 1 insertion(+), 1 deletion(-)

切換到master分支：

$ git switch master
Switched to branch 'master'
Your branch is ahead of 'origin/master' by 1 commit.
  (use "git push" to publish your local commits)

Git還會自動提示我們當前master分支比遠程的master分支要超前1個提交。

在master分支上把readme.txt文件的最后一行改為：

Creating a new branch is quick & simple.

提交：

$ git add readme.txt 
$ git commit -m "& simple"
[master 5dc6824] & simple
 1 file changed, 1 insertion(+), 1 deletion(-)

現在，master分支和feature1分支各自都分別有新的提交，變成了這樣：

這種情況下，Git無法執行“快速合并”，只能試圖把各自的修改合并起來，但這種合并就可能會有沖突，我們試試看：

$ git merge feature1
Auto-merging readme.txt
CONFLICT (content): Merge conflict in readme.txt
Automatic merge failed; fix conflicts and then commit the result.

果然沖突了!Git告訴我們，readme.txt文件存在沖突，必須手動解決沖突后再提交。git status也可以告訴我們沖突的文件：

$ git status
On branch master
Your branch is ahead of 'origin/master' by 2 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:   readme.txt

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

我們可以直接查看readme.txt的內容：

Git is a distributed version control system.
Git is free software distributed under the GPL.
Git has a mutable index called stage.
Git tracks changes of files.
<<<<<<< HEAD
Creating a new branch is quick & simple.
=======
Creating a new branch is quick AND simple.
>>>>>>> feature1

Git用<<<<<<<，=======，>>>>>>>標記出不同分支的內容，我們修改如下后保存：

Creating a new branch is quick and simple.

再提交：

$ git add readme.txt 
$ git commit -m "conflict fixed"
[master cf810e4] conflict fixed

現在，master分支和feature1分支變成了下圖所示：

用帶參數的git log也可以看到分支的合并情況：

$ git log --graph --pretty=oneline --abbrev-commit
*   cf810e4 (HEAD -> master) conflict fixed
|\  
| * 14096d0 (feature1) AND simple
* | 5dc6824 & simple
|/  
* b17d20e branch test
* d46f35e (origin/master) remove test.txt
* b84166e add test.txt
* 519219b git tracks changes
* e43a48b understand how stage works
* 1094adb append GPL
* e475afc add distributed
* eaadf4e wrote a readme file

最后，刪除feature1分支：

$ git branch -d feature1
Deleted branch feature1 (was 14096d0).

工作完成。

小結

當Git無法自動合并分支時，就必須首先解決沖突。解決沖突后，再提交，合并完成。

解決沖突就是把Git合并失敗的文件手動編輯為我們希望的內容，再提交。

用git log --graph命令可以看到分支合并圖。