How to remove file and commit from history in git(git中如何移除 commit 曆史紀錄)

假設我們的 commit tree 如下：

R–A–B–C–D–E–HEAD

準備工作：

 rm -rf .git test.txt

 touch test.txt && git init && git add .
 echo "R" >> test.txt && git ci -a -m "R"
 echo "A" >> test.txt && git ci -a -m "A"
 echo "B" >> test.txt && git ci -a -m "B"
 echo "C" >> test.txt && git ci -a -m "C"
 echo "D" >> test.txt && git ci -a -m "D"
 echo "E" >> test.txt && git ci -a -m "E"

接下來要移除 B 跟 C 的 commit tree，變成

R–A -- D–E–HEAD

這兒有兩種方法移除 B & C：

方法一：

# detach head and move to D commit
git checkout <SHA1-for-D>

# move HEAD to A, but leave the index and working tree as for D
git reset --soft <SHA1-for-A>

# Redo the D commit re-using the commit message, but now on top of A
git commit -C <SHA1-for-D>

在這兒，你可以增加，刪除（某些意外提交的臨時檔案）然後提交。

# Re-apply everything from the old D onwards onto this new place 
git rebase --onto HEAD <SHA1-for-D> master

# push it
git push --force

方法二：  利用 cherry-pick

git rereset --hard <SHA1 of A>
git cherry-pick <SHA1 of D>
git cherry-pick <SHA1 of E>

中間可能出現的問題

http://rwmj.wordpress.com/2010/05/14/git-cherry-pick-wins/

If it’s unable to apply the patch directly, then you’ll see a message

like this:

  Automatic cherry-pick failed.  After resolving the conflicts,
  mark the corrected paths with 'git add <paths>' or 'git rm <paths>' and commit the result.
  When commiting, use the option '-c 94e310d' to retain authorship and message.

This is fairly self-explanatory. Use “git status” to see which files
are problematic:

Edit the file to manually resolve the conflict, add the file, and then
commit with the “-c” option noted in the original message.

cherry-pick不好的地方在於，如果有D後面有多次提交的話，要多次執行該命令，而且可能有衝突需要手動解決。

這兩種方法都會直接忽略 B 跟 C 的 history,，但是B 和C 所做更改依然存在，只是把
commit history移出了而已。

詳細資料可以查詢 git help cherry-pick 或者是 git help rebase

參考：
Git: removing selected commits from repository
http://stackoverflow.com/questions/495345/git-removing-selected-commits-from-repository
Git: how to remove file and commit from history
http://bogdan.org.ua/2009/02/13/git-how-to-remove-file-commit-from-history.html
Re: ! [rejected] master -> master (non-fast forward)
http://kerneltrap.org/mailarchive/git/2007/11/18/425729