超級有用的git reset –hard和git revert命令

很多時候，git新手容易誤操作，比如，在levelIISZ-1.4.dev分支下，運行了git pull idc cpp-1.0的結果，這樣做麻煩很大，經常導致maven項目格式不正確，這個時候，可以用git reset --hard 去撤銷這次修改
但是這樣做也有問題，可能之前本地的，沒有提交的修改，都消失了。可以嘗試git revert命令

reset是指將當前head的內容重設，不會留任何痕迹。

Sets the current head to the specified commit and optionally resets the index and working tree to match. 

 git reset --hard HEAD~3

會將最新的3次提交全部重設，就像沒有提交過一樣。

根據--soft --mixed --hard，會對working tree和index和HEAD進行重設。

revert是撤銷某次提交，但是這次撤銷也會作為一次提交進行儲存(這樣就不會丟失原來修改過，但是沒有提交的內容？)。

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非常好的一篇文章

http://alpha-blog.wanglianghome.org/2010/07/30/git-partial-rollback/

如何使用git回退部分修改

人總有犯錯誤的時候，如果發現不小心把私貨提交到公用程式碼程式庫，改如何挽回呢？

例如如下程式碼程式庫：

$ mkdir git-partial-revert
$ cd git-partial-revert
$ echo "hello a" >a.txt
$ echo "hello b" >b.txt
$ git init
Initialized empty Git repository in /home/liang/project/git/git-partial-revert/.git/
$ git add *.txt
$ git commit -m "initial version"
[master (root-commit) b5e1a24] initial version
 2 files changed, 2 insertions(+), 0 deletions(-)
 create mode 100644 a.txt
 create mode 100644 b.txt
$ git log
commit b5e1a24fc65202977b903435750dd9fb5e0d04d0
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 13:20:38 2010 +0800

 initial version

以下是一次錯誤的修改。

$ echo "hello a from b" >>a.txt
$ echo "hello b from a" >>b.txt
$ git commit -a -m "hello a from b"
[master df3144e] hello a from b
 2 files changed, 2 insertions(+), 0 deletions(-)
$ git push origin master
$ git log
commit df3144e3168f6ec189ed0b2b57908d8d4e862fe5
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 13:22:51 2010 +0800

 hello a from b

commit b5e1a24fc65202977b903435750dd9fb5e0d04d0
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 13:20:38 2010 +0800

 initial version

錯誤在於只應該提交對於a.txt的修改，b.txt的修改是私貨，應該留在本地，以後提交。

第一種方法：純手工修改。取決於要修改的內容多少，這可能是最簡單也可能是最笨的方法。

如果錯誤發生在最新的commit裡面，可以使用git reset修改。如下：

$ git reset b5e1a24f -- b.txt
Unstaged changes after reset:
M       b.txt
$ cat b.txt
hello b
hello b from a
$ git log
commit df3144e3168f6ec189ed0b2b57908d8d4e862fe5
Author: Liang Wang <lwang1@marvell.com>
Date:   Fri Jul 30 13:22:51 2010 +0800

 hello a from b

commit b5e1a24fc65202977b903435750dd9fb5e0d04d0
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 13:20:38 2010 +0800

 initial version
$ git diff
diff --git a/b.txt b/b.txt
index b1bdbca..ab47375 100644
--- a/b.txt
+++ b/b.txt
@@ -1 +1,2 @@
 hello b
+hello b from a
$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#       modified:   b.txt
#
# Changed but not updated:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       modified:   b.txt
#
$ git diff --cached
diff --git a/b.txt b/b.txt
index ab47375..b1bdbca 100644
--- a/b.txt
+++ b/b.txt
@@ -1,2 +1 @@
 hello b
-hello b from a
$ git commit -m "revert change in b"
[master d49f9f2] revert change in b
 1 files changed, 0 insertions(+), 1 deletions(-)
$ git push origin master
$ git status
# On branch master
# Changed but not updated:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       modified:   b.txt
#
no changes added to commit (use "git add" and/or "git commit -a")
$ git diff
diff --git a/b.txt b/b.txt
index b1bdbca..ab47375 100644
--- a/b.txt
+++ b/b.txt
@@ -1 +1,2 @@
 hello b
+hello b from a
$ git log --stat
commit d49f9f2531ed9106ea53006bd698bbcdd54698e9
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 13:34:43 2010 +0800

 revert change in b

 b.txt |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

commit df3144e3168f6ec189ed0b2b57908d8d4e862fe5
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 13:22:51 2010 +0800

 hello a from b

 a.txt |    1 +
 b.txt |    1 +
 2 files changed, 2 insertions(+), 0 deletions(-)

commit b5e1a24fc65202977b903435750dd9fb5e0d04d0
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 13:20:38 2010 +0800

 initial version

 a.txt |    1 +
 b.txt |    1 +
 2 files changed, 2 insertions(+), 0 deletions(-)

這時b的修改就從公用程式碼程式庫上拿掉了，但是還保留在本地。

或者也可以使用git revert。下面操作的缺點是沒有保留對於b.txt的修改。如何保留修改留給讀者作為習題

$ git revert -n df3144e31
Finished one revert.
$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#       modified:   a.txt
#       modified:   b.txt
#
$ git diff --cached
diff --git a/a.txt b/a.txt
index 2c5e468..74614c9 100644
--- a/a.txt
+++ b/a.txt
@@ -1,2 +1 @@
 hello a
-hello a from b
diff --git a/b.txt b/b.txt
index ab47375..b1bdbca 100644
--- a/b.txt
+++ b/b.txt
@@ -1,2 +1 @@
 hello b
-hello b from a
$ git reset HEAD a.txt
Unstaged changes after reset:
M       a.txt
$ cat a.txt
hello a
$ git checkout -- a.txt
$ cat a.txt
hello a
hello a from b
$ cat b.txt
hello b
$ git commit -m "revert change in b"
[master 5f6a2e1] revert change in b
 1 files changed, 0 insertions(+), 1 deletions(-)
$ git log --stat
commit 5f6a2e16bfd59281d0150e3644aa1485dd6c0078
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 14:17:44 2010 +0800

 revert change in b

 b.txt |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

commit df3144e3168f6ec189ed0b2b57908d8d4e862fe5
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 13:22:51 2010 +0800

 hello a from b

 a.txt |    1 +
 b.txt |    1 +
 2 files changed, 2 insertions(+), 0 deletions(-)

commit b5e1a24fc65202977b903435750dd9fb5e0d04d0
Author: Liang Wang <a@b.c>
Date:   Fri Jul 30 13:20:38 2010 +0800

 initial version

 a.txt |    1 +
 b.txt |    1 +
 2 files changed, 2 insertions(+), 0 deletions(-)

如果錯誤的修改已經不是最新的commit，則只能使用git revert。

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我們teamleader的總結，很不錯的！！！

http://guibin.iteye.com/blog/101436