Re: trailers: --only-trailers normalizes URLs to trailers

[Jeff King <peff@peff.net>]

On Thu, Jun 04, 2026 at 11:27:51PM +0200, Kristoffer Haugsbakk wrote:

> The following is a bug that follows straightforwardly from the documented
> or discussed behavior. In that sense it is not a bug. But it is a bug in
> the sense that it makes things inconvenient and violates a design goal.

Yeah, though if you'll allow me to nitpick your subject a moment: I
don't think --only-trailers is really the culprit here. It demonstrates
the problem because it normalizes the "trailer" it found. But the loose
trailer matching is the more fundamental issue. For example:

git interpret-trailers --trailer=foo=bar <<\EOF
subject

body

http://example.com
EOF

will stick the new "foo: bar" trailer right up against the (now-broken)
"http:" trailer. When it should come in its own stanza, which it would
if you added a line "other" at the end, since that tells us that "http:"
can't be a trailer.

> > What's different between what you expected and what actually happened?
> 
> In an ideal world to have some special-casing of URLs so that they are
> not detected as trailers. Does anyone realistically want trailers like
> this?:
> 
>     file: //...
>     http: //...
>     https: //...

I could even see those as trailers, if somebody really wanted to allow
arbitrary values that might just happen to start with "//". But without
the whitespace after the colon, it is quite questionable.

> Just special-casing `https` would go a long way.

Agreed, though I think a rule like: ":// (with no whitespace)" is not a
valid separator. Something like this:

diff --git a/trailer.c b/trailer.c
index 6d8ec7fa8d..342ed81c78 100644
--- a/trailer.c
+++ b/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)) {
+			/* special case to avoid accidental URL matches */
+			if (*c == ':' && c[1] == '/' && c[2] == '/')
+				return -1;
 			return c - line;
+		}
 		if (!whitespace_found && (isalnum(*c) || *c == '-'))
 			continue;
 		if (c != line && (*c == ' ' || *c == '\t')) {

-Peff