finally document initremote type=git

doc/special_remotes.mdwn

@@ -24,6 +24,7 @@ the git history is not stored in them.
 * [[tor]]
 * [[web]]
 * [[webdav]]
+* [[git]]
 * [[xmpp]]
 
 The above special remotes are built into git-annex, and can be used

doc/special_remotes/git.mdwn

@@ -0,0 +1,28 @@
+Normally a git repository is not treated as a special remote, but as a git
+remote of the normal kind. Two exceptions to that are [[git-lfs]] and
+[[gcrypt]] special remotes.
+
+But it is possible to register a git repository as a special remote.
+git-annex will use it remote the same as any normal git remote, but its
+url will be recorded. One benefit of doing this is it allows [[git-annex-init]]
+to autoenable the remote.
+
+First you need a regular git remote with the url that you want to use for
+the special remote.
+
+	git remote add tmpremote ssh://...
+
+Then, to set up the special remote:
+
+	git annex initremote myremote type=git location=ssh://... autoenable=true
+
+Now `git annex init` in each clone of the repository will autoenable myremote.
+
+Note that the name of the git remote (`tmpremote` above) has to be
+different than the name you later use for the special remote,
+since [[git-annex-initremote]] will refuse to use the name of an existing
+remote. To work around that, you could finish by removing `tmpremote` and 
+enable the special remote:
+
+	git remote remove tmpremote
+	git annex enableremote myremote