[PATCH 2 of 2 V2] contrib: add a minimal extension enabling obsolescence

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at logilab.fr>
# Date 1358821461 -3600
# Branch stable
# Node ID e9421379b2f2ba7e5941d4b0361897c897d9c5ec
# Parent  9f92ee2c969579d2c65cafaccffd938f82303982
contrib: add a minimal extension enabling obsolescence

Changeset evolution is still not ready for prime time but we made huge progress
toward it. The evolve extension is still necessary for daily usage client side,
but a very simple extension in contrib will helps on two topics:

1) setting up server:

   The evolve extension only adds new clients commands and UI message. It has no
   added value for a server. Moreover, the evolve extension still have a
   dependency to the debase extension that increase the amount of noise that an
   administrator need to activate on a server.

   Having this little extensions available in contrib will help people to setup
   server with obsolescence which is very valuable to find bug and collect
    future statistics.

2) testing:

   I expect a lot of third party codes and extensions to be incompatible with
   filtering. Having this extension around will help to setup simple
   instructions for testing them with this aspect of 2.5.

diff --git a/contrib/obs.py b/contrib/obs.py
new file mode 100644
--- /dev/null
+++ b/contrib/obs.py
@@ -0,0 +1,10 @@
+'''enable experimental obsolescence feature of Mercurial
+
+OBSOLESCENCE IS AN EXPERIMENTAL FEATURE MAKE SURE YOU UNDERSTOOD THE INVOLVED
+CONCEPT BEFORE USING IT.
+
+For client side usages it is recommended to use the evolve extension for
+improved user interface.'''
+
+import mercurial.obsolete
+mercurial.obsolete._enabled = True