git commit --amend
修改刚才提交的commit信息
撤销 git commit --amend
思路是使用 git reflog 查看在哪里ammend的.找到HEAD{N},
N是ammend之前的那个数.
然后使用git reset --soft HEAD@{N}
see at http://stackoverflow.com/questions/1459150/how-to-undo-git-commit-amend-done-instead-of-git-commit
# Move the current head so that it's pointing at the old commit
# Leave the index intact for redoing the commit
git reset --soft HEAD@{1}
# commit the current tree using the commit details of the previous
# HEAD commit. (Note that HEAD@{1} is pointing somewhere different from the
# previous command. It's now pointing at the erroneously amended commit.)
git commit -C HEAD@{1}