Add a mirror configuration example

Signed-off-by:  <stefhen.hovland+github@gmail.com>

example.conf

@@ -53,6 +53,8 @@ daemon = yes
 # homelink = http://example.com/
 
 ## Set a mirror for all repository
+## (all repositories with a post-receive hook
+##  running "gitosis-run-hook update-mirrors")
 [mirror github]
 repos = @all
 uri = git@github.com:res0nat0r/%s.git

mirror.conf

@@ -0,0 +1,24 @@
+## Mirroring is possible for any repository with
+## the gitosis default post-receive hooks.
+## This hook need to run "gitosis-run-hook update-mirrors"
+
+[gitosis]
+## Create a repository alias
+public = bar baz
+
+## The public repositories have to be mirrored
+## on a github account
+[mirror github]
+repos = @public
+uri = git@github.com:alice/%s.git
+## %s will be replaced by the repository name
+
+[group admin]
+members = alice
+writable = gitosis
+
+## The developpers have access some private repository
+## and to all the public repositories 
+[group dev-team]
+members = bob @admin
+writable = foo @public