Teach bash completion about recent log long options

(Somewhat) recently git-log learned about --reverse (to show commits
in the opposite order) and a looong time ago I think it learned
about --raw (to show the raw diff, rather than a unified diff).
These are both useful options, so we should make them easy for the
user to complete.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

contrib/completion/git-completion.bash

@@ -592,13 +592,13 @@ _git_log ()
 		__gitcomp "
 			--max-count= --max-age= --since= --after=
 			--min-age= --before= --until=
-			--root --topo-order --date-order
+			--root --topo-order --date-order --reverse
 			--no-merges
 			--abbrev-commit --abbrev=
 			--relative-date
 			--author= --committer= --grep=
 			--all-match
-			--pretty= --name-status --name-only
+			--pretty= --name-status --name-only --raw
 			--not --all
 			"
 		return