Warn user when set committers and commit committers differ

[chiptopher]

Feature Request

Description

When appending a commit message with the intention of changing the authors, one might do something like this:

$ guet set initials1 initials2
$ git commit -m "Initial commit"
$ guet set initials2 initials3
$ git commit --amend

However, if they don't supply the --reset-author flag to the git commit, the author will remain initials1. It would be nice if a warning that told them there is a mismatch between the currently set committers and the committers on the commit.

Example

$ guet set initials1 initials2
$ git commit -m "Initial commit"
$ guet set initials2 initials3
$ git commit --amend
The guet committers are set to "initials2 initials3", but the most recently amended
commit has the committers set to "initials1 initials2". To reset the author of the
commit you must include the --reset-author command.