Git报错Unable to create 'XXX/.

Commit failed with error
0 files committed, XX files failed to commit: XXX
Unable to create 'XXX/.git/index.lock': File exists.

Another git process seems to be running in this repository, e.g.
an editor opened by 'git commit'. Please make sure all processes
are terminated then try again. If it still fails, a git process
may have crashed in this repository earlier:
remove the file manually to continue.

解决方法：
在.git同级目录，执行rm -f .git/index.lock