format-patch: do not wrap non-rfc2047 headers too early

Do not wrap the second and later lines of non-rfc2047-encoded headers
substantially before the 78 character limit.

Instead of passing the remaining length of the first line as wrapping
width, use the correct maximum length and tell strbuf_add_wrapped_bytes()
how many characters of the first line are already used.

Signed-off-by: Jan H. Schönherr <schnhrr@cs.tu-berlin.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pretty.c

@@ -286,7 +286,7 @@ static void add_rfc2047(struct strbuf *sb, const char *line, int len,
 		if ((i + 1 < len) && (ch == '=' && line[i+1] == '?'))
 			goto needquote;
 	}
-	strbuf_add_wrapped_bytes(sb, line, len, 0, 1, max_length - line_len);
+	strbuf_add_wrapped_bytes(sb, line, len, -line_len, 1, max_length);
 	return;
 
 needquote:

t/t4014-format-patch.sh

@@ -752,16 +752,14 @@ M64=$M8$M8$M8$M8$M8$M8$M8$M8
 M512=$M64$M64$M64$M64$M64$M64$M64$M64
 cat >expect <<'EOF'
 Subject: [PATCH] foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo
- bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar
+ bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar
- foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo
+ foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo
- bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar
+ bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar
- foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo
+ foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo
- bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar
+ bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar
- foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo
+ foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar
- bar foo bar foo bar foo bar foo bar foo bar foo bar foo bar
- foo bar foo bar foo bar foo bar
 EOF
-test_expect_success 'format-patch wraps extremely long headers (ascii)' '
+test_expect_success 'format-patch wraps extremely long subject (ascii)' '
 	echo content >>file &&
 	git add file &&
 	git commit -m "$M512" &&
@@ -807,28 +805,12 @@ test_expect_success 'format-patch wraps extremely long headers (rfc2047)' '
 	test_cmp expect subject
 '
 
-M8="foo_bar_"
-M64=$M8$M8$M8$M8$M8$M8$M8$M8
-cat >expect <<EOF
-From: $M64
- <foobar@foo.bar>
-EOF
-test_expect_success 'format-patch wraps non-quotable headers' '
-	rm -rf patches/ &&
-	echo content >>file &&
-	git add file &&
-	git commit -mfoo --author "$M64 <foobar@foo.bar>" &&
-	git format-patch --stdout -1 >patch &&
-	sed -n "/^From: /p; /^ /p; /^$/q" <patch >from &&
-	test_cmp expect from
-'
-
 check_author() {
 	echo content >>file &&
 	git add file &&
 	GIT_AUTHOR_NAME=$1 git commit -m author-check &&
 	git format-patch --stdout -1 >patch &&
-	grep ^From: patch >actual &&
+	sed -n "/^From: /p; /^ /p; /^$/q" <patch >actual &&
 	test_cmp expect actual
 }
 
@@ -853,6 +835,32 @@ test_expect_success 'rfc2047-encoded headers also double-quote 822 specials' '
 	check_author "Föo B. Bar"
 '
 
+cat >expect <<EOF
+From: foo_bar_foo_bar_foo_bar_foo_bar_foo_bar_foo_bar_foo_bar_foo_bar_
+ <author@example.com>
+EOF
+test_expect_success 'format-patch wraps moderately long from-header (ascii)' '
+	check_author "foo_bar_foo_bar_foo_bar_foo_bar_foo_bar_foo_bar_foo_bar_foo_bar_"
+'
+
+cat >expect <<'EOF'
+From: Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar
+ Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo
+ Bar Foo Bar Foo Bar Foo Bar <author@example.com>
+EOF
+test_expect_success 'format-patch wraps extremely long from-header (ascii)' '
+	check_author "Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar"
+'
+
+cat >expect <<'EOF'
+From: "Foo.Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar
+ Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo
+ Bar Foo Bar Foo Bar Foo Bar" <author@example.com>
+EOF
+test_expect_success 'format-patch wraps extremely long from-header (rfc822)' '
+	check_author "Foo.Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar Foo Bar"
+'
+
 cat >expect <<'EOF'
 Subject: header with . in it
 EOF