git-merge

1.merge说明

git merge <branch>把指定branch合并到当前分支

.git目录下会多出ORIG_HEAD文件

2.合并操作

2-1.当前分支没有提交

合并 dev分支到master分支时，如果master分支的状态没有被更改过，那么这个合并是非常简单的。 dev分支的历史记录包含master分支所有的历史记录，所以通过把master分支的位置移动到dev的最新分支上，Git 就会合并。这样的合并被称为快进合并(fast-forward)

2-1-1.查看分支情况

2-1-1-1.dev分支日志

dev比master多个dev_a.txt和dev_b.txt提交

git log --oneline --graph

* 0df0755 (HEAD -> dev) add dev_b.txt
* 1b60089 add dev_a.txt
* f8efdee (master) add b.txt
* 40ee907 add a.txt

2-1-1-2.master分支日志

git log --oneline --graph

* f8efdee (HEAD -> master) add b.txt
* 40ee907 add a.txt

2-1-2.合并dev分支

需要先切换到master分支

git merge dev

Updating f8efdee..0df0755
Fast-forward
 dev_a.txt | 1 +
 dev_b.txt | 1 +
 2 files changed, 2 insertions(+)
 create mode 100644 dev_a.txt
 create mode 100644 dev_b.txt

2-1-3.查看master分支日志

现在master和dev都指向了最新的

git log --oneline --graph

* 0df0755 (HEAD -> master, dev) add dev_b.txt
* 1b60089 add dev_a.txt
* f8efdee add b.txt
* 40ee907 add a.txt

2-2.当前分支有新的提交

master分支的历史记录有可能在dev分支分叉出去后有新的更新。这种情况下，要把master分支的修改内容和dev分支的修改内容汇合起来。因此，合并两个修改会生成一个提交。这时，master分支的HEAD会移动到该提交上。

2-2-1.查看分支情况

git log --oneline --graph --all

* eabe74b (HEAD -> master) add c.txt
* 8fc52fd master update a.txt
* 270a873 add b.txt
| * e005e0d (dev) add dev.txt
|/  
* ea2ca92 add a.txt

2-2-2.合并dev分支

需要先切换到master分支

git merge dev

2-2-3.编辑合并信息

Merge branch 'dev'

* dev:
  add dev.txt
# Please enter a commit message to explain why this merge is necessary,
# especially if it merges an updated upstream into a topic branch.
#
# Lines starting with '#' will be ignored, and an empty message aborts
# the commit.

Merge made by the 'recursive' strategy.
 dev.txt | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 dev.txt

2-2-4.查看commit信息

git log -1

Merge: 2b18a2a e005e0d
Author: user_name <xxxx@xx.com>
Date:   Wed Jul 5 17:40:08 2023 +0800

    Merge branch 'dev'
    
    * dev:
      add dev.txt

2-2-5.查看日志

git log --oneline --graph --all

*   8384f46 (HEAD -> master) Merge branch 'dev'
|\  
| * e005e0d (dev) add dev.txt
* | 2b18a2a add c.txt
* | 8fc52fd master update a.txt
* | 270a873 add b.txt
|/  
* ea2ca92 add a.txt

3.合并冲突

3-1.查看分支情况

git log --oneline --graph --all

* 392675b (HEAD -> master) add c.txt
* 8fc52fd master update a.txt
* 270a873 add b.txt
| * 526ed91 (dev) add dev1.txt
| * d3f1159 dev update a.txt
| * e005e0d add dev.txt
|/  
* ea2ca92 add a.txt

3-2.合并dev分支(冲突)

需要先切换到master分支

git merge dev

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

3-3.查看状态

git status

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

Changes to be committed:
        new file:   dev.txt
        new file:   dev1.txt

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

3-4.修改冲突文件

3-4-1.冲突位置

a
<<<<<<< HEAD
master
=======
dev
>>>>>>> dev

3-4-2.修改完成(都保留)

a
master
dev

3-4-3.把冲突文件添加到暂存区

git add a.txt

3-4-4.再次查看状态

git status

On branch master
All conflicts fixed but you are still merging.
  (use "git commit" to conclude merge)

Changes to be committed:
        modified:   a.txt
        new file:   dev.txt
        new file:   dev1.txt

3-5.继续合并

git commit

[master d0fbf37] Merge branch 'dev'

3-6.查看日志

git log --oneline --graph --all

*   d0fbf37 (HEAD -> master) Merge branch 'dev'
|\  
| * 526ed91 (dev) add dev1.txt
| * d3f1159 dev update a.txt
| * e005e0d add dev.txt
* | 392675b add c.txt
* | 8fc52fd master update a.txt
* | 270a873 add b.txt
|/  
* ea2ca92 add a.txt

4.撤销合并

2-1-1.合并基础上进行撤销merge

4-1.查看reflog日志

git:(master) git reflog

0df0755 (HEAD -> master, dev) HEAD@{0}: merge dev: Fast-forward	# 这是刚才合并记录
f8efdee HEAD@{1}: checkout: moving from dev to master						# 这个是merge之前的记录
0df0755 (HEAD -> master, dev) HEAD@{2}: commit: add dev_b.txt
1b60089 HEAD@{3}: commit: add dev_a.txt
f8efdee HEAD@{4}: checkout: moving from master to dev
f8efdee HEAD@{5}: commit: add b.txt
40ee907 HEAD@{6}: commit (initial): add a.txt

4-2.撤销

等同于git reset --hard HEAD~2

git reset --merge f8efdee

4-3.查看log日志

master已经变为了2条记录了

git log --oneline --graph

* f8efdee (HEAD -> master) add b.txt
* 40ee907 add a.txt

4-4.查看reflog日志

git reflog

f8efdee (HEAD -> master) HEAD@{0}: reset: moving to f8efdee
0df0755 (dev) HEAD@{1}: merge dev: Fast-forward
f8efdee (HEAD -> master) HEAD@{2}: checkout: moving from dev to master
0df0755 (dev) HEAD@{3}: commit: add dev_b.txt
1b60089 HEAD@{4}: commit: add dev_a.txt
f8efdee (HEAD -> master) HEAD@{5}: checkout: moving from master to dev
f8efdee (HEAD -> master) HEAD@{6}: commit: add b.txt
40ee907 HEAD@{7}: commit (initial): add a.txt