Unify appending signoff in format-patch, commit and sequencer

There are two implementations of append_signoff in log-tree.c and
sequencer.c, which do more or less the same thing.  Unify on top of the
sequencer.c implementation.

Add a test in t4014 to demonstrate support for non-s-o-b elements in the
commit footer provided by sequence.c:append_sob.  Mark tests fixed as
appropriate.

[Commit message mostly stolen from Nguyễn Thái Ngọc Duy's original
 unification patch]

Signed-off-by: Brandon Casey <bcasey@nvidia.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

log-tree.c

@@ -9,8 +9,7 @@
 #include "string-list.h"
 #include "color.h"
 #include "gpg-interface.h"
-
+#include "sequencer.h"
-#define APPEND_SIGNOFF_DEDUP (1u <<0)
 
 struct decoration name_decoration = { "object names" };
 
@@ -208,94 +207,6 @@ void show_decorations(struct rev_info *opt, struct commit *commit)
 	putchar(')');
 }
 
-/*
- * Search for "^[-A-Za-z]+: [^@]+@" pattern. It usually matches
- * Signed-off-by: and Acked-by: lines.
- */
-static int detect_any_signoff(char *letter, int size)
-{
-	char *cp;
-	int seen_colon = 0;
-	int seen_at = 0;
-	int seen_name = 0;
-	int seen_head = 0;
-
-	cp = letter + size;
-	while (letter <= --cp && *cp == '\n')
-		continue;
-
-	while (letter <= cp) {
-		char ch = *cp--;
-		if (ch == '\n')
-			break;
-
-		if (!seen_at) {
-			if (ch == '@')
-				seen_at = 1;
-			continue;
-		}
-		if (!seen_colon) {
-			if (ch == '@')
-				return 0;
-			else if (ch == ':')
-				seen_colon = 1;
-			else
-				seen_name = 1;
-			continue;
-		}
-		if (('A' <= ch && ch <= 'Z') ||
-		    ('a' <= ch && ch <= 'z') ||
-		    ch == '-') {
-			seen_head = 1;
-			continue;
-		}
-		/* no empty last line doesn't match */
-		return 0;
-	}
-	return seen_head && seen_name;
-}
-
-static void append_signoff(struct strbuf *sb, int ignore_footer, unsigned flag)
-{
-	unsigned no_dup_sob = flag & APPEND_SIGNOFF_DEDUP;
-	static const char signed_off_by[] = "Signed-off-by: ";
-	char *signoff = xstrdup(fmt_name(getenv("GIT_COMMITTER_NAME"),
-					       getenv("GIT_COMMITTER_EMAIL")));
-	size_t signoff_len = strlen(signoff);
-	int has_signoff = 0;
-	char *cp;
-
-	cp = sb->buf;
-
-	/* First see if we already have the sign-off by the signer */
-	while ((cp = strstr(cp, signed_off_by))) {
-
-		has_signoff = 1;
-
-		cp += strlen(signed_off_by);
-		if (cp + signoff_len >= sb->buf + sb->len)
-			break;
-		if (strncmp(cp, signoff, signoff_len))
-			continue;
-		if (!isspace(cp[signoff_len]))
-			continue;
-		/* we already have him */
-		free(signoff);
-		return;
-	}
-
-	if (!has_signoff)
-		has_signoff = detect_any_signoff(sb->buf, sb->len);
-
-	if (!has_signoff)
-		strbuf_addch(sb, '\n');
-
-	strbuf_addstr(sb, signed_off_by);
-	strbuf_add(sb, signoff, signoff_len);
-	strbuf_addch(sb, '\n');
-	free(signoff);
-}
-
 static unsigned int digits_in_number(unsigned int number)
 {
 	unsigned int i = 10, result = 1;

t/t4014-format-patch.sh

@@ -1045,7 +1045,28 @@ EOF
 	test_cmp expected actual
 '
 
-test_expect_failure 'signoff: some random signoff-alike' '
+test_expect_success 'signoff: misc conforming footer elements' '
+	append_signoff <<\EOF >actual &&
+subject
+
+body
+
+Signed-off-by: my@house
+(cherry picked from commit da39a3ee5e6b4b0d3255bfef95601890afd80709)
+Tested-by: Some One <someone@example.com>
+Bug: 1234
+EOF
+	cat >expected <<\EOF &&
+4:Subject: [PATCH] subject
+8:
+10:
+11:Signed-off-by: my@house
+15:Signed-off-by: C O Mitter <committer@example.com>
+EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'signoff: some random signoff-alike' '
 	append_signoff <<\EOF >actual &&
 subject
 
@@ -1061,7 +1082,7 @@ EOF
 	test_cmp expected actual
 '
 
-test_expect_failure 'signoff: not really a signoff' '
+test_expect_success 'signoff: not really a signoff' '
 	append_signoff <<\EOF >actual &&
 subject
 
@@ -1077,7 +1098,7 @@ EOF
 	test_cmp expected actual
 '
 
-test_expect_failure 'signoff: not really a signoff (2)' '
+test_expect_success 'signoff: not really a signoff (2)' '
 	append_signoff <<\EOF >actual &&
 subject
 
@@ -1094,7 +1115,7 @@ EOF
 	test_cmp expected actual
 '
 
-test_expect_failure 'signoff: valid S-o-b paragraph in the middle' '
+test_expect_success 'signoff: valid S-o-b paragraph in the middle' '
 	append_signoff <<\EOF >actual &&
 subject
 
@@ -1162,7 +1183,7 @@ EOF
 	test_cmp expected actual
 '
 
-test_expect_failure 'signoff: detect garbage in non-conforming footer' '
+test_expect_success 'signoff: detect garbage in non-conforming footer' '
 	append_signoff <<\EOF >actual &&
 subject