trailer: handle NULL value when parsing trailer-specific config

When parsing the "key", "command", and "cmd" trailer config, we just
make a copy of the value string.  If we see an implicit bool like:

  [trailer "foo"]
  key

we'll segfault trying to copy a NULL pointer. We can fix this with the
usual config_error_nonbool() check.

I split this out from the other vanilla cases, because at first glance
it looks like a better fix here would be to move the NULL check out of
the switch statement. But it would change the behavior of other keys
like trailer.*.ifExists, where an implicit bool is interpreted as
EXISTS_DEFAULT.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/trailer.c b/trailer.c
index b0e2ec224a2fa16ab0f87012a5b0a4bf90996760..e4b08ed267fa9aa0c3c1535b636b70edc21c70cb 100644 (file)
--- a/trailer.c
+++ b/trailer.c
@@ -553,16 +553,22 @@ static int git_trailer_config(const char *conf_key, const char *value,
        case TRAILER_KEY:
                if (conf->key)
                        warning(_("more than one %s"), conf_key);
+               if (!value)
+                       return config_error_nonbool(conf_key);
                conf->key = xstrdup(value);
                break;
        case TRAILER_COMMAND:
                if (conf->command)
                        warning(_("more than one %s"), conf_key);
+               if (!value)
+                       return config_error_nonbool(conf_key);
                conf->command = xstrdup(value);
                break;
        case TRAILER_CMD:
                if (conf->cmd)
                        warning(_("more than one %s"), conf_key);
+               if (!value)
+                       return config_error_nonbool(conf_key);
                conf->cmd = xstrdup(value);
                break;
        case TRAILER_WHERE: