Re: [PATCH 3/8] daemon: recognize hidden request arguments

> 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.
> 
> In order to get around this limitation teach git-daemon to recognize
> additional request arguments hidden behind a second NUL byte.  Requests
> can then be structured like:
> "command path/to/repo\0host=..\0\0version=1\0key=value\0".  git-daemon
> can then parse out the extra arguments and set 'GIT_PROTOCOL'
> accordingly.

> @@ -574,7 +583,7 @@ static void canonicalize_client(struct strbuf *out, const char *in)
>  /*
>   * Read the host as supplied by the client connection.
>   */
> -static void parse_host_arg(struct hostinfo *hi, char *extra_args, int buflen)
> +static char *parse_host_arg(struct hostinfo *hi, char *extra_args, int buflen)
>  {
>  	char *val;
>  	int vallen;
> @@ -602,6 +611,39 @@ static void parse_host_arg(struct hostinfo *hi, char *extra_args, int buflen)
>  		if (extra_args < end && *extra_args)
>  			die("Invalid request");
>  	}
> +
> +	return extra_args;
> +}
> +
> +static void parse_extra_args(struct argv_array *env, const char *extra_args,
> +			     int buflen)
> +{
> +	const char *end = extra_args + buflen;
> +	struct strbuf git_protocol = STRBUF_INIT;
> +
> +	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);
>  }