git-gui: Expose the browser as a subcommand.
git-gui: Expose the browser as a subcommand.

Some users may find being able to browse around an arbitrary
branch to be handy, so we now expose our graphical browser
through `git gui browse <committish>`.

Yes, I'm being somewhat lazy and making the user give us
the name of the branch to browse.  They can always enter
HEAD.

Signed-off-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>
destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git