On some systems, help2man produces color codes in the output. Remove
them to avoid manpage churn.
Also begin adding unit tests.
Change-Id: I3f0204b19d9cae524d3cb5fcfb61ee309b0931fc
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/349655
Tested-by: LaMont Jones <lamontjones@google.com>
Reviewed-by: Xin Li <delphij@google.com>