Editing An Incorrect Commit Message In Git

To fix an incorrect commit message to the head of a repository use the following command:

git commit --amend

This will allow you to enter a new message for the previous commit. From stack overflow:

Used to amend the tip of the current branch. Prepare the tree object you would want to replace the latest commit as usual (this includes the usual -i/-o and explicit paths), and the commit log editor is seeded with the commit message from the tip of the current branch. The commit you create replaces the current tip – if it was a merge, it will have the parents of the current tip as parents – so the current top commit is discarded.

It is a rough equivalent for:

$ git reset --soft HEAD^
$ ... do something else to come up with the right tree ...
$ git commit -c ORIG_HEAD

but can be used to amend a merge commit.