https://fedorahosted.org/fedora-packager/ticket/64

Add man page generator to generate a man page at build time.

usage: fedpkg.py initial-merge [-h] [-n] [repo-path [repo-path ...]]

Performs a 'git merge' of all git branches with the same content
(i.e. with the same package spec files, patch files, etc.), regardless
of their history.

This is useful after Fedora's dist-cvs to dist-git migration, as often
different branches have different histories but the same content on the
filesystem.

After these initial merges of identical trees, future merges between
the branches will be a lot easier: Easier to follow in the dependency
graph, and easier to perform without conflicts.

positional arguments:
  repo-path      Path to a repo to initial-merge

optional arguments:
  -h, --help     show this help message and exit
  -n, --dry-run  Whether to run without actually merging

Move the argparse setup and the actual argument parsing into
a separate parse_cmdline function.

This makes the actual main program more clear, and allows
reusing of the argparse setup for man page generation later.