doc: add '-d' and '-o' for 'git push'

Add the missing `-o` shortcut for `--push-option` to the synopsis.
Add the missing `-d` shortcut for `--delete` in the main section.

Signed-off-by: Andreas Heiduk <asheiduk@gmail.com>
Reviewed-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-push.txt

@@ -11,7 +11,7 @@ SYNOPSIS
 [verse]
 'git push' [--all | --mirror | --tags] [--follow-tags] [--atomic] [-n | --dry-run] [--receive-pack=<git-receive-pack>]
 	   [--repo=<repository>] [-f | --force] [-d | --delete] [--prune] [-v | --verbose]
-	   [-u | --set-upstream] [--push-option=<string>]
+	   [-u | --set-upstream] [-o <string> | --push-option=<string>]
 	   [--[no-]signed|--signed=(true|false|if-asked)]
 	   [--force-with-lease[=<refname>[:<expect>]]]
 	   [--no-verify] [<repository> [<refspec>...]]
@@ -123,6 +123,7 @@ already exists on the remote side.
 	will be tab-separated and sent to stdout instead of stderr.  The full
 	symbolic names of the refs will be given.
 
+-d::
 --delete::
 	All listed refs are deleted from the remote repository. This is
 	the same as prefixing all refs with a colon.