Merge branch 'kh/trailers-no-urls'

The trailer parsing machinery has been updated to avoid mistaking
lines that begin with a URL (e.g., 'https://...') as trailer lines.
This prevents intended textual URLs from being mangled or mistakenly
treated as metadata keys.

* kh/trailers-no-urls:
  trailers: stop recognizing URLs as trailers

Documentation/git-interpret-trailers.adoc

@@ -123,9 +123,16 @@ OTHER RULES
 What was covered in the previous section are the rules that are relevant
 for regular use. The following points are included for completeness.
 
-This command ignores comment lines (see `core.commentString` in
-linkgit:git-config[1]). This is for use with the `prepare-commit-msg`
-and `commit-msg` hooks.
+--
+* This command ignores comment lines (see `core.commentString` in
+  linkgit:git-config[1]). This is for use with the `prepare-commit-msg`
+  and `commit-msg` hooks.
+
+* Candidate trailer lines that have `:` as the separator, that have no
+  whitespace before the value part, and that start with `//` are not
+  recognized as trailers. This is to avoid accidentally interpreting
+  URLs as trailers (e.g. lines that start with `https://`).
+--
 
 OPTIONS
 -------

t/t7513-interpret-trailers.sh

@@ -1989,4 +1989,23 @@ test_expect_success 'handling of --- lines in conjunction with cut-lines' '
 	test_cmp expected actual
 '
 
+test_expect_success 'URLs and lines that are not quite URLs' '
+	cat >expect <<-\EOF &&
+	https: //www.a-trailer.org
+	https: //www.another-trailer.org
+	Signed-off-by: somebody <somebody@somewhere>
+	EOF
+	git interpret-trailers --only-trailers >actual <<-\EOF &&
+	subject
+
+	body
+
+	https://www.not-a-trailer.org
+	https ://www.a-trailer.org
+	https: //www.another-trailer.org
+	Signed-off-by: somebody <somebody@somewhere>
+	EOF
+	test_cmp expect actual
+'
+
 test_done

t/unit-tests/u-trailer.c

@@ -318,3 +318,55 @@ void test_trailer__one_non_trailer_no_git_trailers(void)
 			   0,
 			   expected_contents);
 }
+
+void test_trailer__URL(void)
+{
+	struct contents expected_contents[] = { 0 };
+
+	t_trailer_iterator("Subject: foo bar\n"
+			   "\n"
+			   /*
+			    * We do not want to match URLs as trailers.
+			    */
+			   "https://www.example.org\n",
+			   0,
+			   expected_contents);
+}
+
+void test_trailer__not_a_URL_space_after_separator(void)
+{
+	struct contents expected_contents[] = {
+		{ .raw = "https: //www.example.org\n",
+		  .key = "https",
+		  .val = "//www.example.org" },
+		{ 0 },
+	};
+
+	t_trailer_iterator("Subject: foo bar\n"
+			   "\n"
+			   /*
+			    * This has a space after ':' so it's not a URL.
+			    */
+			   "https: //www.example.org\n",
+			   1,
+			   expected_contents);
+}
+
+void test_trailer__not_a_URL_space_before_separator(void)
+{
+	struct contents expected_contents[] = {
+		{ .raw = "https ://www.example.org\n",
+		  .key = "https",
+		  .val = "//www.example.org" },
+		{ 0 },
+	};
+
+	t_trailer_iterator("Subject: foo bar\n"
+			   "\n"
+			   /*
+			    * This has a space before ':' so it's not a URL.
+			    */
+			   "https ://www.example.org\n",
+			   1,
+			   expected_contents);
+}

trailer.c

@@ -635,8 +635,12 @@ static ssize_t find_separator(const char *line, const char *separators)
 	int whitespace_found = 0;
 	const char *c;
 	for (c = line; *c; c++) {
-		if (strchr(separators, *c))
+		if (strchr(separators, *c)) {
+			/* avoid accidental URL matches */
+			if (!whitespace_found && starts_with(c, "://"))
+				return -1;
 			return c - line;
+		}
 		if (!whitespace_found && (isalnum(*c) || *c == '-'))
 			continue;
 		if (c != line && (*c == ' ' || *c == '\t')) {