Add git_branch option to specify a branch to checkout
Add --force option to force write SRPM even when git repo was not updated.

This does not update the package Version of Release, just regenerates the SRPM.
Useful when there's a typo in .spec file or something and you need to redo the
SRPM.
Add 'realname' option to be used in changelog instead of username

When the realname option is not specified, username option is used instead.
This is to make it possible to use different name in changelog than is
username in COPR.
Add copr_name option to specify COPR in which all SRPMs should be built

Rather than having one copr for each package, we want to build multiple packages
in one COPR. For that we specify the COPR name on 'copr_name' option and use it
in API calls.
Update authors