git详解(三）回退操作
2016-11-27 21:40
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git详解(三）回退操作
摘要： 在我们使用git修改文件需要回到修改之前的状态时，就需要git的回退操作，回退操作对于我们很重要，本文主要介绍关于git回退操作的内容。包括git reset ,git checkout。通过本文，我们可以对git的回退操作有一个很好的理解。关键字: 回退，reset, checkout
git详解三回退操作
git logreflog
git reset
git checkout
conclusion
１. git log/reflog
master这个引用指向我们最新的提交，类似于一个游标，通过git reset可以对游标进行修改。fox@fox:~/Documents/demo$ git log --oneline 539d895 add new.log ba7f561 commit 0e94145 add test.txt fox@fox:~/Documents/demo$ git reset --hard ba7f561 fox@fox:~/Documents/demo$ git log --oneline ba7f561 commit 0e94145 add test.txt
发现在执行git reset的时候,master发生了变化，git log也随之进行了变化，那么问题来了，是不是我们只能git reset 历史commit呢？也就是这样的游标只能往后，不能往前，其实不是的。我们继续看一下提交log。
fox@fox:~/Documents/demo$ cat .git/logs/refs/heads/master 0000000000000000000000000000000000000000 0e94145e01eb5da2420dd8a47d103aeab1dff44b fox <leehaoran111@163.com> 1476806519 +0800 commit (initial): add test.txt 0e94145e01eb5da2420dd8a47d103aeab1dff44b ba7f561a2798f2b41a7131888bdbc58531ba89c5 fox <leehaoran111@163.com> 1478435045 +0800 commit: commit ba7f561a2798f2b41a7131888bdbc58531ba89c5 d4c1f0765b0b58ce464d95989f2ebfe4094f4f54 fox <leehaoran111@163.com> 1478439077 +0800 commit: ok d4c1f0765b0b58ce464d95989f2ebfe4094f4f54 ba7f561a2798f2b41a7131888bdbc58531ba89c5 fox <leehaoran111@163.com> 1480241004 +0800 reset: moving to HEAD^ ba7f561a2798f2b41a7131888bdbc58531ba89c5 539d8955e8820776f914d93f5778e2025884f0a6 fox <leehaoran111@163.com> 1480241093 +0800 commit: add new.log 539d8955e8820776f914d93f5778e2025884f0a6 ba7f561a2798f2b41a7131888bdbc58531ba89c5 fox <leehaoran111@163.com> 1480241299 +0800 reset: moving to HEAD^ ba7f561a2798f2b41a7131888bdbc58531ba89c5 539d8955e8820776f914d93f5778e2025884f0a6 fox <leehaoran111@163.com> 1480242249 +0800 reset: moving to 539d895 539d8955e8820776f914d93f5778e2025884f0a6 ba7f561a2798f2b41a7131888bdbc58531ba89c5 fox <leehaoran111@163.com> 1480242306 +0800 reset: moving to ba7f561 fox@fox:~/Documents/demo$ git cat-file -p 539d8955 tree b5f005e70497d197ba637c9576621beda3ec7233 parent ba7f561a2798f2b41a7131888bdbc58531ba89c5 author fox <leehaoran111@163.com> 1480241093 +0800 committer fox <leehaoran111@163.com> 1480241093 +0800 add new.log fox@fox:~/Documents/demo$ git cat-file -p b5f005e 100644 blob 6594dfffc7a1e8b880c02eb5f97d11caef98a6d0 new.log 100644 blob 7aeee4f72cc77cc564fcc3aa7fd03caea3542fcb test.txt fox@fox:~/Documents/demo$ git cat-file -p 6594dfff git reset demo
发现可以在git 的提交log中找到历史的master commit id. 也就是539d8955e88。
通过git reset 539d8955e88 会发现new.log又回来了。
fox@fox:~/Documents/demo$ git reset --hard 539d8955e HEAD is now at 539d895 add new.log fox@fox:~/Documents/demo$ ll total 20 drwxrwxr-x 3 fox fox 4096 11月 27 18:35 ./ drwxr-xr-x 10 fox fox 4096 11月 6 22:06 ../ drwxrwxr-x 8 fox fox 4096 11月 27 18:35 .git/ -rw-rw-r-- 1 fox fox 15 11月 27 18:35 new.log -rw-rw-r-- 1 fox fox 45 11月 6 21:18 test.txt
前面log文件中记录的master变化是顺序的，也就是最新的在最下面，git reflog可以看到倒序的变化，这样方便我们查看。
fox@fox:~/Documents/demo$ git reflog
539d895 HEAD@{0}: reset: moving to 539d8955e
ba7f561 HEAD@{1}: reset: moving to ba7f561a
539d895 HEAD@{2}: reset: moving to 539d8955e
ba7f561 HEAD@{3}: reset: moving to ba7f56
539d895 HEAD@{4}: reset: moving to 539d8955e8
ba7f561 HEAD@{5}: reset: moving to ba7f561
539d895 HEAD@{6}: reset: moving to 539d895
ba7f561 HEAD@{7}: reset: moving to HEAD^
539d895 HEAD@{8}: commit: add new.log
ba7f561 HEAD@{9}: reset: moving to HEAD^
d4c1f07 HEAD@{10}: commit: ok
ba7f561 HEAD@{11}: commit: commit
0e94145 HEAD@{12}: commit (initial): add test.txt这样，我们可以通过git log 和git reflog就可以查看之前之后的提交commit id.
2. git reset
在知道了怎样查找commit id之后，我们就可以借助git reset来按照我们的需求切换commit id了。git reset可以加路径也可以不加路径，加路径表示更改一个文件。
git reset [--soft | --mixed [-N] | --hard | --merge | --keep] [-q] [<commit>]
git reset 后面加–soft,–hard,–mixed是有区别的，这也经常会用到，我们举一个例子看一下区别
step 1:let us create a file demo.c fox@fox:~/Documents/demo$ git st On branch master Untracked files: (use "git add <file>..." to include in what will be committed) demo.c nothing added to commit but untracked files present (use "git add" to track) fox@fox:~/Documents/demo$ git add * fox@fox:~/Documents/demo$ git st On branch master Changes to be committed: (use "git reset HEAD <file>..." to unstage) new file: demo.c fox@fox:~/Documents/demo$ git reset --hard HEAD HEAD is now at 539d895 add new.log fox@fox:~/Documents/demo$ git st On branch master nothing to commit, working directory clean fox@fox:~/Documents/demo$ ll total 20 drwxrwxr-x 3 fox fox 4096 11月 27 19:02 ./ drwxr-xr-x 10 fox fox 4096 11月 6 22:06 ../ drwxrwxr-x 8 fox fox 4096 11月 27 19:02 .git/ -rw-rw-r-- 1 fox fox 15 11月 27 18:35 new.log -rw-rw-r-- 1 fox fox 45 11月 6 21:18 test.txt 发现用--hard时，staging和工作区的修改和ＨＥＡＤ一样了。同时工作区demo.c也不见了。这时要恢复demo.c就比较麻烦了，需要在objects里面挨个找了。 我们新建一个ｄｅｍｏ.c，继续看--mixed fox@fox:~/Documents/demo$ echo "i am demo.c" >demo.c fox@fox:~/Documents/demo$ git st On branch master Untracked files: (use "git add <file>..." to include in what will be committed) demo.c nothing added to commit but untracked files present (use "git add" to track) fox@fox:~/Documents/demo$ git add * fox@fox:~/Documents/demo$ git st On branch master Changes to be committed: (use "git reset HEAD <file>..." to unstage) new file: demo.c fox@fox:~/Documents/demo$ git reset --mixed HEAD fox@fox:~/Documents/demo$ git st On branch master Untracked files: (use "git add <file>..." to include in what will be committed) demo.c nothing added to commit but untracked files present (use "git add" to track) 可以看到--mixed用mstaer中的内容覆盖staging中的内容，但不修改工作区的修改。而且--mixed是默认的选项。 能猜到，--soft的话就是仅仅修改HEAD指向的commit id,不影响staging和工作区。
3 git checkout
git reset可以在当前分支中切换commit id,但是当我们想到切换HEAD指向的分支时该怎么办呢？我们知道在每一次git commit的时候，都是当前的HEAD指向的commit id会成为父提交。这时候就需要用到checkout.checkout也是经常会用到的一个命令。git checkout [-q] [-f] [-m] [<branch>] git checkout [-q] [-f] [-m] --detach [<branch>] git checkout [-q] [-f] [-m] [--detach] <commit> git checkout [-q] [-f] [-m] [[-b|-B|--orphan] <new_branch>] [<start_point>] git checkout [-f|--ours|--theirs|-m|--conflict=<style>] [<tree-ish>] [--] <paths>... git checkout [-p|--patch] [<tree-ish>] [--] [<paths>...] checkout有以下用法： 用法一：分支切换： fox@fox:~/Documents/demo$ git br fixbug * master fox@fox:~/Documents/demo$ git co fixbug Switched to branch 'fixbug' fox@fox:~/Documents/demo$ git br * fixbug master 用法二：显示staging和版本库的区别： fox@fox:~/Documents/demo$ ll total 16 drwxrwxr-x 3 fox fox 4096 11月 27 21:23 ./ drwxr-xr-x 10 fox fox 4096 11月 6 22:06 ../ drwxrwxr-x 8 fox fox 4096 11月 27 21:24 .git/ -rw-rw-r-- 1 fox fox 45 11月 6 21:18 test.txt fox@fox:~/Documents/demo$ echo "add more" >> test.txt fox@fox:~/Documents/demo$ git st On branch fixbug Changes not staged for commit: (use "git add <file>..." to update what will be committed) (use "git checkout -- <file>..." to discard changes in working directory) modified: test.txt no changes added to commit (use "git add" and/or "git commit -a") fox@fox:~/Documents/demo$ git add test.txt fox@fox:~/Documents/demo$ git st On branch fixbug Changes to be committed: (use "git reset HEAD <file>..." to unstage) modified: test.txt fox@fox:~/Documents/demo$ git co M test.txt 用法三：用其它分支的文件代替本分支staging和工作区的文件： fox@fox:~/Documents/demo$ git cat-file -p master:new.log git reset demo fox@fox:~/Documents/demo$ ll total 16 drwxrwxr-x 3 fox fox 4096 11月 27 21:28 ./ drwxr-xr-x 10 fox fox 4096 11月 6 22:06 ../ drwxrwxr-x 8 fox fox 4096 11月 27 21:28 .git/ -rw-rw-r-- 1 fox fox 45 11月 27 21:28 test.txt fox@fox:~/Documents/demo$ git co master new.log fox@fox:~/Documents/demo$ git st On branch fixbug Changes to be committed: (use "git reset HEAD <file>..." to unstage) new file: new.log fox@fox:~/Documents/demo$ cat new.log git reset demo 用法四： 撤销工作区的修改： fox@fox:~/Documents/demo$ echo "retort some demo" >> test.txt fox@fox:~/Documents/demo$ git st On branch fixbug Changes not staged for commit: (use "git add <file>..." to update what will be committed) (use "git checkout -- <file>..." to discard changes in working directory) modified: test.txt no changes added to commit (use "git add" and/or "git commit -a") fox@fox:~/Documents/demo$ git co . fox@fox:~/Documents/demo$ git st On branch fixbug nothing to commit, working directory clean
4 conclusion
this blog show some usage of git reset and git checkout, which can help us change the commit id the HEAD pointed to ,then we can cancel or renew some modifies on staging or workspace.
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