git rebase 作用

git rabase（变基）常用三个功能：

• 分支合并
• 合并commit
• 更改commit信息

1. 合并分支

原理是将当前分支与要rebase的分支进行比较，找到两条分支的共同节点，然后将当前分支变基到master上，并创建一个临时文件c4，然后切换到master分支上，并进行一次merge，此时master和experiment分支都指向了c4，此时可以删除experiment分支。

$ git checkout experiment
$ git rebase master
$ git checkout master
$ git merge experiment

​ 与merge的区别是，merge会创建一个新的merge节点同时指向c3，c4。所以merge会保留c4的commit信息，而rebase在c4'会重新提交包含c3和c4的commit信息。merge更能保存信息，rebase更简洁，保证分支的提交是线性的。

​ merge后分支情况如下：

2. 合并commit

当前git log如下

$ git log --graph --oneline
* 853b82d (HEAD -> test) commit3
* 3802571 commit2
* d231bc8 commit1

使用git rebase -i 来指定需要合并节点的父节点，如果要合并commit2和commit3，指定commit1的log id，然后自动弹出vim来修改commit（注意这里的commit的顺序与git log的顺序是相反的！）。将pick修改为s表示此commit会被上一个commit合并，即新提交的commit合并到旧的commit上。

$ git rebase -i d231bc8

pick 3802571 commit2
pick 853b82d commit3

# Rebase d231bc8..853b82d onto d231bc8 (2 commands)
#
# Commands:
# p, pick <commit> = use commit

pick 3802571 commit2
s 853b82d commit3

# Rebase d231bc8..853b82d onto d231bc8 (2 commands)
#
# Commands:
# p, pick <commit> = use commit

将pick修改为s后可以修改commit message：

# This is a combination of 2 commits.
# This is the 1st commit message:

commit2

# This is the commit message #2:

commit3

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Date:      Sat Jun 11 13:59:58 2022 +0800

此时commit3已合并到commit2中

$ git log --oneline --graph
* dc30c78 (HEAD -> test) commit2
* d231bc8 commit1

commit2的message如下：

commit dc30c78c979b4974ba29c2e17eb2c1787a8bd6f3 (HEAD -> test)
Author: 
Date:   Sat Jun 11 13:59:58 2022 +0800

    commit2

    commit3

3. 更改commit信息

commit信息如下，要修改commit2的message，需要使用git rebase -i指定父节点的log ID，在这即commit1的ID

$ git log --oneline --graph
* dc30c78 (HEAD -> test) commit2
* d231bc8 commit1

commit2的message如下：

commit dc30c78c979b4974ba29c2e17eb2c1787a8bd6f3 (HEAD -> test)
Author: 
Date:   Sat Jun 11 13:59:58 2022 +0800

    commit2

    commit3

$ git rebase -i d231bc8

vim将pick修改为r修改提交信息

pick dc30c78 commit2

# Rebase d231bc8..dc30c78 onto d231bc8 (1 command)
#

s dc30c78 commit2

# Rebase d231bc8..dc30c78 onto d231bc8 (1 command)
#

将commit2和commit3修改到一行上

commit2 commit3

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# Date:      Sat Jun 11 13:59:58 2022 +0800

git log 查看commit2的message

commit c6e822ac8d84d17da4668b530667573c345dccf7 (HEAD -> test)
Author: 
Date:   Sat Jun 11 13:59:58 2022 +0800

    commit2 commit3

其中 pick , s , r 参数的含义如下：