[PATCH 09/11] format-patch: stricter S-o-b detection

[Brandon Casey <drafnel@gmail.com>]

From: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>

S-o-b in the middle of a sentence, at the beginning of the sentence
but it is just because of text wrapping, or a full paragraph of valid
S-o-b in the middle of the message. All these are not S-o-b, but
detected as is. Fix them.

[bc: add two additional tests to demonstrate shortcomings of the current
   code:

   1. failure to detect non-conforming elements in the footer when last
      line matches committer's s-o-b.
   2. failure to handle various s-o-b -like elements in the footer as
      conforming. e.g. "Change-id: IXXXX or Bug: 1234"

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Brandon Casey <bcasey@nvidia.com>
---
 log-tree.c              | 37 +++++++++++++++++--
 t/t4014-format-patch.sh | 95 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 130 insertions(+), 2 deletions(-)

diff --git a/log-tree.c b/log-tree.c
index 4f86def..14ebf69 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -260,14 +260,47 @@ static void append_signoff(struct strbuf *sb, const char *signoff)
 	int has_signoff = 0;
 	char *cp;
 
-	cp = sb->buf;
+	/*
+	 * Only search in the last paragrah, don't be fooled by a
+	 * paragraph full of valid S-o-b in the middle.
+	 */
+	cp = sb->buf + sb->len - 1;
+	while (cp > sb->buf) {
+		if (cp[0] == '\n' && cp[1] == '\n') {
+			cp += 2;
+			break;
+		}
+		cp--;
+	}
 
 	/* First see if we already have the sign-off by the signer */
 	while ((cp = strstr(cp, signed_off_by))) {
+		const char *s = cp;
+		cp += strlen(signed_off_by);
+
+		if (!has_signoff && s > sb->buf) {
+			/*
+			 * S-o-b in the middle of a sentence is not
+			 * really S-o-b
+			 */
+			if (s[-1] != '\n')
+				continue;
+
+			if (s - 1 > sb->buf && s[-2] == '\n')
+				; /* the first S-o-b */
+			else if (!detect_any_signoff(sb->buf, s - sb->buf))
+				/*
+				 * The previous line looks like an
+				 * S-o-b. There's still no guarantee
+				 * that it's an actual S-o-b. For that
+				 * we need to look back until we find
+				 * a blank line, which is too costly.
+				 */
+				continue;
+		}
 
 		has_signoff = 1;
 
-		cp += strlen(signed_off_by);
 		if (cp + signoff_len >= sb->buf + sb->len)
 			break;
 		if (strncmp(cp, signoff, signoff_len))
diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
index dfe9209..30e37a7 100755
--- a/t/t4014-format-patch.sh
+++ b/t/t4014-format-patch.sh
@@ -1062,6 +1062,60 @@ EOF
 	test_cmp expected actual
 '
 
+test_expect_success 'signoff: not really a signoff' '
+	append_signoff <<\EOF >actual &&
+subject
+
+I want to mention about Signed-off-by: here.
+EOF
+	cat >expected <<\EOF &&
+4:Subject: [PATCH] subject
+8:
+9:I want to mention about Signed-off-by: here.
+10:
+11:Signed-off-by: C O Mitter <committer@example.com>
+EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'signoff: not really a signoff (2)' '
+	append_signoff <<\EOF >actual &&
+subject
+
+My unfortunate
+Signed-off-by: example happens to be wrapped here.
+EOF
+	cat >expected <<\EOF &&
+4:Subject: [PATCH] subject
+8:
+10:Signed-off-by: example happens to be wrapped here.
+11:
+12:Signed-off-by: C O Mitter <committer@example.com>
+EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'signoff: valid S-o-b paragraph in the middle' '
+	append_signoff <<\EOF >actual &&
+subject
+
+Signed-off-by: my@house
+Signed-off-by: your@house
+
+A lot of houses.
+EOF
+	cat >expected <<\EOF &&
+4:Subject: [PATCH] subject
+8:
+9:Signed-off-by: my@house
+10:Signed-off-by: your@house
+11:
+13:
+14:Signed-off-by: C O Mitter <committer@example.com>
+EOF
+	test_cmp expected actual
+'
+
 test_expect_success 'signoff: the same signoff at the end' '
 	append_signoff <<\EOF >actual &&
 subject
@@ -1109,4 +1163,45 @@ EOF
 	test_cmp expected actual
 '
 
+test_expect_failure 'signoff: detect garbage in non-conforming footer' '
+	append_signoff <<\EOF >actual &&
+subject
+
+body
+
+Tested-by: my@house
+Some Trash
+Signed-off-by: C O Mitter <committer@example.com>
+EOF
+	cat >expected <<\EOF &&
+4:Subject: [PATCH] subject
+8:
+10:
+13:Signed-off-by: C O Mitter <committer@example.com>
+14:
+15:Signed-off-by: C O Mitter <committer@example.com>
+EOF
+	test_cmp expected actual
+'
+
+test_expect_failure 'signoff: footer begins with non-signoff without @ sign' '
+	append_signoff <<\EOF >actual &&
+subject
+
+body
+
+Tested-by: my@house
+Change-id: Ideadbeef
+Signed-off-by: C O Mitter <committer@example.com>
+Bug: 1234
+EOF
+	cat >expected <<\EOF &&
+4:Subject: [PATCH] subject
+8:
+10:
+13:Signed-off-by: C O Mitter <committer@example.com>
+EOF
+	test_cmp expected actual
+'
+
 test_done
-- 
1.8.0.284.g959048a