Add a HOWTO for setting up a standalone git daemon

Setting up a git-daemon came up the other day on IRC, and it is slightly
non trivial for the uninitiated.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/howto/use-git-daemon.txt

@@ -0,0 +1,52 @@
+How to use git-daemon
+
+Git can be run in inetd mode and in stand alone mode. But all you want is
+let a coworker pull from you, and therefore need to set up a git server
+real quick, right?
+
+Note that git-daemon is not really chatty at the moment, especially when
+things do not go according to plan (e.g. a socket could not be bound).
+
+Another word of warning: if you run
+
+	$ git ls-remote git://127.0.0.1/rule-the-world.git
+
+and you see a message like
+
+	fatal: The remote end hung up unexpectedly
+
+it only means that _something_ went wrong. To find out _what_ went wrong,
+you have to ask the server. (Git refuses to be more precise for your
+security only. Take off your shoes now. You have any coins in your pockets?
+Sorry, not allowed -- who knows what you planned to do with them?)
+
+With these two caveats, let's see an example:
+
+	$ git daemon --reuseaddr --verbose --base-path=/home/gitte/git \
+	  --export-all -- /home/gitte/git/rule-the-world.git
+
+(Of course, unless your user name is `gitte` _and_ your repository is in
+~/rule-the-world.git, you have to adjust the paths. If your repository is
+not bare, be aware that you have to type the path to the .git directory!)
+
+This invocation tries to reuse the address if it is already taken
+(this can save you some debugging, because otherwise killing and restarting
+git-daemon could just silently fail to bind to a socket).
+
+Also, it is (relatively) verbose when somebody actually connects to it.
+It also sets the base path, which means that all the projects which can be
+accessed using this daemon have to reside in or under that path.
+
+The option `--export-all` just means that you _don't_ have to create a
+file named `git-daemon-export-ok` in each exported repository. (Otherwise,
+git-daemon would complain loudly, and refuse to cooperate.)
+
+Last of all, the repository which should be exported is specified. It is
+a good practice to put the paths after a "--" separator.
+
+Now, test your daemon with
+
+	$ git ls-remote git://127.0.0.1/rule-the-world.git
+
+If this does not work, find out why, and submit a patch to this document.
+