show: add basic labels to work template
`hg show work` is much more usable if output is colored. This patch
implements coloring via label() in a very hacky way.
In a default Mercurial install, you'll see yellow node labels for all
phases. Branches and bookmarks use the same formatting as the commit
message. So this change doesn't help much in a default install. But if
you have a custom colors defined for these things, output is much more
readable.
The implementation obviously needs some work. But for a minor change
on a feature that isn't convered by BC, this seems like a clear win
for the feature in 4.2.
#require docutils gettext
$ $TESTDIR/check-gendoc ru
checking for parse errors