commit: more compact summary and without extra quotes

Update the report format again to save the screen real estates, while
avoiding from enclosing the one-line summary of the commit log inside
double quotes pair, which looks awkward when the message begins or ends
with a double quote.  The old format looked like this:

    [master]: created d9a5491: "foo:bar"

Simply removing the double quotes were found to be confusing as a message
often begins with a short-word (area of the system) and a colon.

The new format looks like this:

    [master d9a5491] foo:bar

As discussed in the git mailing list:

    http://thread.gmane.org/gmane.comp.version-control.git/101687/focus=101735Signed-off-by: NSanti Béjar <santi@agolina.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-commit.c

@@ -883,7 +883,7 @@ static void print_summary(const char *prefix, const unsigned char *sha1)
 {
 	struct rev_info rev;
 	struct commit *commit;
-	static const char *format = "format:%h: \"%s\"";
+	static const char *format = "format:%h] %s";
 	unsigned char junk_sha1[20];
 	const char *head = resolve_ref("HEAD", junk_sha1, 0, NULL);
 
@@ -910,7 +910,7 @@ static void print_summary(const char *prefix, const unsigned char *sha1)
 	rev.diffopt.break_opt = 0;
 	diff_setup_done(&rev.diffopt);
 
-	printf("[%s%s]: created ",
+	printf("[%s%s ",
 		!prefixcmp(head, "refs/heads/") ?
 			head + 11 :
 			!strcmp(head, "HEAD") ?