git 手动master_git pull --rebase的正确使用
在多人使用同一个远程分支合作开发的时候，很可能出现 push 代码的时候出现以下问题：
$ git push origin master
# 结果如下
To github.com:hello/demo.git
! [rejected] master -> master (fetch first)
error: failed to push some refs to '[email protected]:hello/demo.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
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很明显此时远程分支有新的 commit 未同步到本地，无法推送。正常情况下我们会执行以下操作：
$ git pull origin master
# 结果如下
remote: Counting objects: 2, done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 2 (delta 1), reused 0 (delta 0)
Unpacking objects: 100% (2/2), done.
From github.com:hello/demo
3824da0..f318a05 master -> origin/master
Merge made by the 'recursive' strategy.
one.md | 2 ++
1 file changed, 2 insertions(+)
$ git push origin master
# 结果如下
Enumerating objects: 10, done.
Counting objects: 100% (8/8), done.
Delta compression using up to 8 threads
Compressing objects: 100% (8/8), done.
Writing objects: 100% (8/8), 1.24 KiB | 1.24 MiB/s, done.
Total 8 (delta 5), reused 0 (delta 0)
To github.com:hello/demo.git
f318a05..1aefef1 master -> master
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确实 push 成功了，但是此时用 git log 查看以下提交记录：
$ git log
# 结果如下
commit 1aefef1a2bedbd3ebd82db8dcf802011a35a9888 (HEAD -> master, origin/master, origin/HEAD)
Merge: 24cfa5c f318a05
Author: hello
Date: Tue Jul 23 09:53:47 2019 +0800
Merge branch 'master' of github.com:hello/demo
commit 24cfa5c3ad271e85ff0e64793bf2bcc9d700c233
Author: hello
Date: Tue Jul 23 09:50:06 2019 +0800
feat: 新功能提交
commit f318a05b1a4cbc0a6cf8d7dc7d3fb99cbafb0363
Author: world
Date: Tue Jul 23 09:48:20 2019 +0800
feat: 其他功能提交
...
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你会发现多出了一条 merge commit，这个 commit 就是在执行 git pull origin master 的时候自动生成的。如果多人多次如此操作，那么提交记录就会出现很多条这种自从生成的 merge commit，非常难看。
要解决以上问题，不再出现自动生成的 merge commit，那么只要在执行 git pull origin master 的时候带上 --rebase 即可：
$ git pull --rebase origin master
$ git push origin master
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项目示例
现在通过一个示例项目来示范以上命令的用法。项目(demo)的结构如下：
# 在 demo 目录下执行以下命令
$ ls
# 结果如下
one.md two.md
$ cat one.md
# 结果如下
hello one
$ cat two.md
#结果如下
hello two
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A、B两位开发同学使用一个远程分支(master)合作开发。A同学修改了 one.md 文件，提交了一个 commit 并且已经推送到远程分支 master：
$ cat one.md
# 结果如下
hello one
new feature for one
$ git push origin master
# 结果如下
Enumerating objects: 4, done.
Counting objects: 100% (4/4), done.
Delta compression using up to 8 threads
Compressing objects: 100% (4/4), done.
Writing objects: 100% (4/4), 1.24 KiB | 1.24 MiB/s, done.
Total 4 (delta 3), reused 0 (delta 0)
To github.com:hello/demo.git
f318a05..1aefef1 master -> master
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此时B同学不知情，也并未将远程分支的更新拉到本地。B同学修改了 two.md 文件，也提交了一个 commit 并尝试推送到远程分支 master：
$ cat two.md
# 结果如下
hello two
new feature for two
$ git push origin master
# 结果如下
To github.com:hello/demo.git
! [rejected] master -> master (fetch first)
error: failed to push some refs to '[email protected]:hello/demo.git'
hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.
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发现报错，无法推送。此时执行以下命令：
$ git pull --rebase
$ git push origin master
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即可成功推送。
注意事项
执行 git pull --rebase 的时候必须保持本地目录干净。即：不能存在状态为 modified 的文件。(存在Untracked files是没关系的)
如果出现冲突，可以选择手动解决冲突后继续 rebase，也可以放弃本次 rebase
执行 git pull --rebase 的时候必须保持本地目录干净
有 modified 状态的文件
本地有受版本控制的文件改动的时候，执行以上命令：
$ git pull --rebase
# 结果如下
error: cannot pull with rebase: You have unstaged changes.
error: please commit or stash them.
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会出现以上报错，无法操作。
此时查看以下文件状态：
$ git status
# 结果如下
On branch master
Your branch is ahead of 'origin/master' by 1 commit.
(use "git push" to publish your local commits)
Changes not staged for commit:
(use "git add ..." to update what will be committed)
(use "git checkout -- ..." to discard changes in working directory)
modified: two.md
no changes added to commit (use "git add" and/or "git commit -a")
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就是因为本地有文件改动尚未提交造成的。此时有两种做法：
如果本次修改已经完成，则可以先提交(commit)一下
如果本次修改尚未完成，则可以先贮藏：git stash
做了以上一种操作之后再尝试 git pull --rebase，不会再报错。
如果做了 git stash 操作，此时可以通过 git stash pop 回到之前的工作状态。
有 Untracked files
查看本地文件状态：
$ git status
# 结果如下
On branch master
Your branch is ahead of 'origin/master' by 1 commit.
(use "git push" to publish your local commits)
Untracked files:
(use "git add ..." to include in what will be committed)
three.md
no changes added to commit (use "git add" and/or "git commit -a")
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如果是以上这种情况，直接执行 git pull --rebase 是不会有问题的。
如果出现冲突，可以选择手动解决冲突后继续 rebase，也可以放弃本次 rebase
在上面的示例项目中，如果 A、B 同学修改了同一个文件。那么很有可能会出现冲突，当 B 同学来执行命令的时候会出现如下状况：
$ git pull --rebase
# 结果如下
remote: Counting objects: 6, done.
remote: Compressing objects: 100% (6/6), done.
remote: Total 6 (delta 1), reused 0 (delta 0)
Unpacking objects: 100% (6/6), done.
From gitlab.lrts.me:fed/gitlab-merge
93a1a93..960b5fc master -> origin/master
First, rewinding head to replay your work on top of it...
Applying: feat: 其他功能提交
Using index info to reconstruct a base tree...
Mone.md
Falling back to patching base and 3-way merge...
Auto-merging one.md
CONFLICT (content): Merge conflict in one.md
error: Failed to merge in the changes.
Patch failed at 0001 feat：其他功能提交
hint: Use 'git am --show-current-patch' to see the failed patch
Resolve all conflicts manually, mark them as resolved with
"git add/rm ", then run "git rebase --continue".
You can instead skip this commit: run "git rebase --skip".
To abort and get back to the state before "git rebase", run "git rebase --abort".
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这种情况下，可以手动打开 one.md 文件解决冲突，然后再执行：
$ git add one.md
$ git rebase --continue
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解决问题。
也可以用 git rebase --abort 放弃本次 rebase 操作。
总结
多人基于同一个远程分支开发的时候，如果想要顺利 push 又不自动生成 merge commit，建议在每次提交都按照如下顺序操作：
$ git stash
$ git pull --rebase
$ git push
$ git stash pop
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