Merge branch 'da/completion-show-signature'

* da/completion-show-signature:
  completion: add --show-signature for log and show

contrib/completion/git-completion.bash

@@ -1467,6 +1467,7 @@ _git_log ()
 			--abbrev-commit --abbrev=
 			--relative-date --date=
 			--pretty= --format= --oneline
+			--show-signature
 			--cherry-pick
 			--graph
 			--decorate --decorate=
@@ -2344,6 +2345,7 @@ _git_show ()
 		;;
 	--*)
 		__gitcomp "--pretty= --format= --abbrev-commit --oneline
+			--show-signature
 			$__git_diff_common_options
 			"
 		return