Re: [PATCH v2 4/9] daemon: recognize hidden request arguments

Brandon Williams [off-list ref] writes:

A normal request to git-daemon is structured as
"command path/to/repo\0host=..\0" and due to a bug in an old version of
git-daemon 73bb33a94 (daemon: Strictly parse the "extra arg" part of the
command, 2009-06-04) we aren't able to place any extra args (separated
by NULs) besides the host.

It's a bit unclear if that commit _introduced_ a bug, or just
noticed an old bug and documented it in its log message.  How does
that commit impact the versons of Git that the updated code is
capable of interracting with?

+static void parse_extra_args(struct hostinfo *hi, struct argv_array *env,
+			     char *extra_args, int buflen)
+{
+	const char *end = extra_args + buflen;
+	struct strbuf git_protocol = STRBUF_INIT;
+
+	/* First look for the host argument */
+	extra_args = parse_host_arg(hi, extra_args, buflen);
+
+	/* Look for additional arguments places after a second NUL byte */
+	for (; extra_args < end; extra_args += strlen(extra_args) + 1) {
+		const char *arg = extra_args;
+
+		/*
+		 * Parse the extra arguments, adding most to 'git_protocol'
+		 * which will be used to set the 'GIT_PROTOCOL' envvar in the
+		 * service that will be run.
+		 *
+		 * If there ends up being a particular arg in the future that
+		 * git-daemon needs to parse specificly (like the 'host' arg)
+		 * then it can be parsed here and not added to 'git_protocol'.
+		 */
+		if (*arg) {
+			if (git_protocol.len > 0)
+				strbuf_addch(&git_protocol, ':');
+			strbuf_addstr(&git_protocol, arg);
+		}
+	}
+
+	if (git_protocol.len > 0)
+		argv_array_pushf(env, GIT_PROTOCOL_ENVIRONMENT "=%s",
+				 git_protocol.buf);
+	strbuf_release(&git_protocol);
 }