format-patch: wrap cover-letter's shortlog sensibly

Earlier, overly-long onelines would not be wrapped at all, and indented
with 6 spaces.

Instead, we now wrap around at 72 characters, with a first-line indent
of 2 spaces, and the rest with 4 spaces.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-log.c

@@ -683,6 +683,10 @@ static void make_cover_letter(struct rev_info *rev, int use_stdout,
 	strbuf_release(&sb);
 
 	shortlog_init(&log);
+	log.wrap_lines = 1;
+	log.wrap = 72;
+	log.in1 = 2;
+	log.in2 = 4;
 	for (i = 0; i < nr; i++)
 		shortlog_add_commit(&log, list[i]);
 

t/t4013/diff.format-patch_--stdout_--cover-letter_-n_initial..master^

@@ -7,8 +7,8 @@ Subject: [DIFFERENT_PREFIX 0/2] *** SUBJECT HERE ***
 *** BLURB HERE ***
 
 A U Thor (2):
-      Second
-      Third
+  Second
+  Third
 
  dir/sub |    4 ++++
  file0   |    3 +++

t/t4014-format-patch.sh

@@ -211,4 +211,23 @@ test_expect_success 'cover-letter inherits diff options' '
 	grep "file => foo .* 0 *$" 0000-cover-letter.patch
 
 '
+
+cat > expect << EOF
+  This is an excessively long subject line for a message due to the
+    habit some projects have of not having a short, one-line subject at
+    the start of the commit message, but rather sticking a whole
+    paragraph right at the start as the only thing in the commit
+    message. It had better not become the filename for the patch.
+  foo
+
+EOF
+
+test_expect_success 'shortlog of cover-letter wraps overly-long onelines' '
+
+	git format-patch --cover-letter -2 &&
+	sed -e "1,/A U Thor/d" -e "/^$/q" < 0000-cover-letter.patch > output &&
+	git diff expect output
+
+'
+
 test_done