git 修改上次提交信息 与 撤销此操作.

git commit --amend

撤销 git commit --amend

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}