Documentation: add upload-archive service to git-daemon.

This patch minimaly documents the upload-archive service,
hoping that someone with better knowledge will improve upon.
Signed-off-by: NChristian Couder <chriscool@tuxfamily.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/git-daemon.txt

@@ -37,6 +37,8 @@ from `git-fetch`, `git-ls-remote`, and `git-clone`.
 This is ideally suited for read-only updates, i.e., pulling from
 git repositories.
 
+An `upload-archive` also exists to serve `git-archive`.
+
 OPTIONS
 -------
 --strict-paths::
@@ -155,6 +157,9 @@ upload-pack::
 	disable it by setting `daemon.uploadpack` configuration
 	item to `false`.
 
+upload-archive::
+	This serves `git-archive --remote`.
+
 EXAMPLES
 --------
 git-daemon as inetd server::