[PATCH 2 of 2] bundle2: add an 'idx' argument to the 'getbundle2partsgenerator'

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at fb.com>
# Date 1429037977 14400
#      Tue Apr 14 14:59:37 2015 -0400
# Node ID c1a731ed65a77904df26631756884d3dd17b5035
# Parent  2ec934ad3f7fdcdf389f99cceeac2bf59a80f705
bundle2: add an 'idx' argument to the 'getbundle2partsgenerator'

This argument let extensions control in what order bundle2 part are generated
server side during a pull. This is useful to ensure the transaction is in a
proper state before some actions or hooks happens.

diff --git a/mercurial/exchange.py b/mercurial/exchange.py
--- a/mercurial/exchange.py
+++ b/mercurial/exchange.py
@@ -1133,11 +1133,11 @@ getbundle2partsorder = []
 # Mapping between step name and function
 #
 # This exists to help extensions wrap steps if necessary
 getbundle2partsmapping = {}
 
-def getbundle2partsgenerator(stepname):
+def getbundle2partsgenerator(stepname, idx=None):
     """decorator for function generating bundle2 part for getbundle
 
     The function is added to the step -> function mapping and appended to the
     list of steps.  Beware that decorated functions will be added in order
     (this may matter).
@@ -1145,11 +1145,14 @@ def getbundle2partsgenerator(stepname):
     You can only use this decorator for new steps, if you want to wrap a step
     from an extension, attack the getbundle2partsmapping dictionary directly."""
     def dec(func):
         assert stepname not in getbundle2partsmapping
         getbundle2partsmapping[stepname] = func
-        getbundle2partsorder.append(stepname)
+        if idx is None:
+            getbundle2partsorder.append(stepname)
+        else:
+            getbundle2partsorder.insert(idx, stepname)
         return func
     return dec
 
 def getbundle(repo, source, heads=None, common=None, bundlecaps=None,
               **kwargs):