git: Improve git log parsing

Make the tag parsing case-insensitive and use regular expressions.

Change-Id: 16c01e4099
review post: Make the output more consistent

Review the review post subcommand and make the output a bit more consistent with
other commands. Also dropped a few funky sentences from the output, it is more
irritating than helping to see the important info. Sorry, I am boring, I know.

Change-Id: bae17f3055