mailinfo: with -b, keep space after [foo]

The logic for the -b mode, where [PATCH] is dropped but [foo] is not,
silently ate all spaces after the ].

Fix this by keeping the next isspace() character, if there is any.
Being more thorough is pointless, as the later cleanup_space() call
will normalize any sequence of whitespace to a single ' '.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/mailinfo.c

@@ -250,8 +250,17 @@ static void cleanup_subject(struct strbuf *subject)
 			    (7 <= remove &&
 			     memmem(subject->buf + at, remove, "PATCH", 5)))
 				strbuf_remove(subject, at, remove);
-			else
+			else {
 				at += remove;
+				/*
+				 * If the input had a space after the ], keep
+				 * it.  We don't bother with finding the end of
+				 * the space, since we later normalize it
+				 * anyway.
+				 */
+				if (isspace(subject->buf[at]))
+					at += 1;
+			}
 			continue;
 		}
 		break;

t/t4150-am.sh

@@ -244,7 +244,7 @@ test_expect_success 'am --keep really keeps the subject' '
 	grep "Re: Re: Re: \[PATCH 1/5 v2\] \[foo\] third" actual
 '
 
-test_expect_failure 'am --keep-non-patch really keeps the non-patch part' '
+test_expect_success 'am --keep-non-patch really keeps the non-patch part' '
 	rm -fr .git/rebase-apply &&
 	git reset --hard &&
 	git checkout HEAD^ &&