builtin-commit: fix --signoff

The Signed-off-by: line contained a spurious timestamp.  The reason was
a call to git_committer_info(1), which automatically added the
timestamp.

Instead, fmt_ident() was taught to interpret an empty string for the
date (as opposed to NULL, which still triggers the default behavior)
as "do not bother with the timestamp", and builtin-commit.c uses it.

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

builtin-commit.c

@@ -183,21 +183,29 @@ static int prepare_log_message(const char *index_file, const char *prefix)
 		die("could not open %s\n", git_path(commit_editmsg));
 
 	stripspace(&sb, 0);
-	if (fwrite(sb.buf, 1, sb.len, fp) < sb.len)
-		die("could not write commit template: %s\n",
-		    strerror(errno));
 
 	if (signoff) {
-		const char *info, *bol;
-
-		info = git_committer_info(1);
-		strbuf_addch(&sb, '\0');
-		bol = strrchr(sb.buf + sb.len - 1, '\n');
-		if (!bol || prefixcmp(bol, sign_off_header))
-			fprintf(fp, "\n");
-		fprintf(fp, "%s%s\n", sign_off_header, git_committer_info(1));
+		struct strbuf sob;
+		int i;
+
+		strbuf_init(&sob, 0);
+		strbuf_addstr(&sob, sign_off_header);
+		strbuf_addstr(&sob, fmt_ident(getenv("GIT_COMMITTER_NAME"),
+					      getenv("GIT_COMMITTER_EMAIL"),
+					      "", 1));
+		strbuf_addch(&sob, '\n');
+
+		for (i = sb.len - 1; i > 0 && sb.buf[i - 1] != '\n'; i--)
+			; /* do nothing */
+		if (prefixcmp(sb.buf + i, sob.buf))
+			strbuf_addbuf(&sb, &sob);
+		strbuf_release(&sob);
 	}
 
+	if (fwrite(sb.buf, 1, sb.len, fp) < sb.len)
+		die("could not write commit template: %s\n",
+		    strerror(errno));
+
 	strbuf_release(&sb);
 
 	if (in_merge && !no_edit)

ident.c

@@ -224,13 +224,17 @@ const char *fmt_ident(const char *name, const char *email,
 	}
 
 	strcpy(date, git_default_date);
-	if (date_str)
-		parse_date(date_str, date, sizeof(date));
+	if (date_str) {
+		if (*date_str)
+			parse_date(date_str, date, sizeof(date));
+		else
+			date[0] = '\0';
+	}
 
 	i = copy(buffer, sizeof(buffer), 0, name);
 	i = add_raw(buffer, sizeof(buffer), i, " <");
 	i = copy(buffer, sizeof(buffer), i, email);
-	i = add_raw(buffer, sizeof(buffer), i, "> ");
+	i = add_raw(buffer, sizeof(buffer), i, date[0] ? "> " : ">");
 	i = copy(buffer, sizeof(buffer), i, date);
 	if (i >= sizeof(buffer))
 		die("Impossibly long personal identifier");

t/t7500-commit.sh

@@ -122,7 +122,19 @@ test_expect_success 'using alternate GIT_INDEX_FILE (2)' '
 
 	) &&
 	cmp .git/index saved-index >/dev/null
+'
 
+cat > expect << EOF
+zort
+Signed-off-by: C O Mitter <committer@example.com>
+EOF
+
+test_expect_success '--signoff' '
+	echo "yet another content *narf*" >> foo &&
+	echo "zort" |
+		GIT_EDITOR=../t7500/add-content git commit -s -F - foo &&
+	git cat-file commit HEAD | sed "1,/^$/d" > output &&
+	diff expect output
 '
 
 test_done