i18n: fix some misformated placeholders in command synopsis

* add '<>' around arguments where missing
 * convert plurals into '...' forms

This applies the style guide for documentation.

Signed-off-by: Jean-Noël Avila <jn.avila@free.fr>
Reviewed-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fast-export.c

@@ -26,7 +26,7 @@
 #include "commit-slab.h"
 
 static const char *fast_export_usage[] = {
-	N_("git fast-export [rev-list-opts]"),
+	N_("git fast-export [<rev-list-opts>]"),
 	NULL
 };
 

builtin/reflog.c

@@ -17,10 +17,10 @@ static const char reflog_expire_usage[] =
 N_("git reflog expire [--expire=<time>] "
    "[--expire-unreachable=<time>] "
    "[--rewrite] [--updateref] [--stale-fix] [--dry-run | -n] "
-   "[--verbose] [--all] <refs>...");
+   "[--verbose] [--all] <ref>...");
 static const char reflog_delete_usage[] =
 N_("git reflog delete [--rewrite] [--updateref] "
-   "[--dry-run | -n] [--verbose] <refs>...");
+   "[--dry-run | -n] [--verbose] <ref>...");
 static const char reflog_exists_usage[] =
 N_("git reflog exists <ref>");
 

builtin/rev-list.c

@@ -20,7 +20,7 @@
 #include "packfile.h"
 
 static const char rev_list_usage[] =
-"git rev-list [OPTION] <commit-id>... [ -- paths... ]\n"
+"git rev-list [<options>] <commit-id>... [-- <path>...]\n"
 "  limiting output:\n"
 "    --max-count=<n>\n"
 "    --max-age=<epoch>\n"