Git alias: fix-index

[kieranpotts]

If a Git operation fails to complete, you can get fatal errors on subsequent commands.

$ git commit -m "message"
fatal: Unable to create '/path/to/.git/index.lock': File exists.

The solution is to remove the index.lock file:

$ rm -f ./.git/index.lock

The scope of this ticket is:

1. To create a Git alias for this command.
2. To suggest using this command whenever another alias encounters this fatal error.