send-pack: properly use parse_options() API for usage string

When "send-pack" was changed to use the parse_options() API in
068c77a (builtin/send-pack.c: use parse_options API, 2015-08-19)
it was made to use one very long line, instead it should split them up
with newlines.

Furthermore we were including an inline explanation that you couldn't
combine "--all" and "<ref>", but unlike in the "blame" case this was
not preceded by an empty string.

Let's instead show that --all and <ref> can't be combined in the the
usual language of the usage syntax instead. We can make it clear that
one of the two options "--foo" and "--bar" is mandatory, but that the
two are mutually exclusive by referring to them as "( --foo | --bar
)".

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-send-pack.txt

@@ -9,10 +9,10 @@ git-send-pack - Push objects over Git protocol to another repository
 SYNOPSIS
 --------
 [verse]
-'git send-pack' [--all] [--dry-run] [--force] [--receive-pack=<git-receive-pack>]
+'git send-pack' [--dry-run] [--force] [--receive-pack=<git-receive-pack>]
 		[--verbose] [--thin] [--atomic]
 		[--[no-]signed|--signed=(true|false|if-asked)]
-		[<host>:]<directory> [<ref>...]
+		[<host>:]<directory> (--all | <ref>...)
 
 DESCRIPTION
 -----------

builtin/send-pack.c

@@ -17,10 +17,10 @@
 #include "protocol.h"
 
 static const char * const send_pack_usage[] = {
-	N_("git send-pack [--all | --mirror] [--dry-run] [--force] "
-	  "[--receive-pack=<git-receive-pack>] [--verbose] [--thin] [--atomic] "
-	  "[<host>:]<directory> [<ref>...]\n"
-	  "  --all and explicit <ref> specification are mutually exclusive."),
+	N_("git send-pack [--mirror] [--dry-run] [--force]\n"
+	   "              [--receive-pack=<git-receive-pack>]\n"
+	   "              [--verbose] [--thin] [--atomic]\n"
+	   "              [<host>:]<directory> (--all | <ref>...)"),
 	NULL,
 };