standardize usage info string format

This patch puts the usage info strings that were not already in docopt-
like format into docopt-like format, which will be a litle easier for
end users and a lot easier for translators. Changes include:

- Placing angle brackets around fill-in-the-blank parameters
- Putting dashes in multiword parameter names
- Adding spaces to [-f|--foobar] to make [-f | --foobar]
- Replacing <foobar>* with [<foobar>...]

Signed-off-by: Alex Henrie <alexhenrie24@gmail.com>
Reviewed-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/merge-file.c

@@ -5,7 +5,7 @@
 #include "parse-options.h"
 
 static const char *const merge_file_usage[] = {
-	N_("git merge-file [options] [-L name1 [-L orig [-L name2]]] file1 orig_file file2"),
+	N_("git merge-file [<options>] [-L <name1> [-L <orig> [-L <name2>]]] <file1> <orig-file> <file2>"),
 	NULL
 };
 
@@ -42,7 +42,7 @@ int cmd_merge_file(int argc, const char **argv, const char *prefix)
 			    N_("for conflicts, use this marker size")),
 		OPT__QUIET(&quiet, N_("do not warn about conflicts")),
 		OPT_CALLBACK('L', NULL, names, N_("name"),
-			     N_("set labels for file1/orig_file/file2"), &label_cb),
+			     N_("set labels for file1/orig-file/file2"), &label_cb),
 		OPT_END(),
 	};