config: give a more detailed sample repo config

Some examples of the typical configurations that one might want to do
in an .hg/hgrc file. This includes a default-push that happens to
point to the same location as my-fork.

I insist on the myfork terminology for a server-side clone. Bitbucket,
Github, and others have widely popularised this meaning of "fork".

This also includes a gentle nudge to use a repo-specific username,
which is something that people might not instinctively realise is an
option.

mercurial/ui.py

@@ -28,6 +28,18 b' username ='
 
     'local':
 """# example repository config (see "hg help config" for more info)
+[paths]
+# path aliases to other clones of this repo in URLs or filesystem paths
+# (see "hg help config.paths" for more info)
+#
+# default      = http://example.com/hg/example-repo
+# default-push = ssh://[e-mail]/hg/jdoes-fork
+# my-fork      = ssh://[e-mail]/hg/jdoes-fork
+# my-clone     = /home/jdoe/jdoes-clone
+
+[ui]
+# name and email (local to this repository, optional), e.g.
+# username = Jane Doe <[e-mail]>
 """,
 
     'global':