getsubset: get the unpacker version from the bundler

getsubset: get the unpacker version from the bundler

The current setup requires to pass both a packer and, optionally, the version
of the unpacker. This is confusing and error prone as the two value cannot
mismatch. Instead, we simply grab the version from the packer. This fixes a bug
where requesting a cg2 from 'hg bundle' were reported as changegroup 1.

I should have caught that in the initial changeset but I missed it somehow.

--- a/mercurial/changegroup.py	Mon Oct 12 15:42:32 2015 +0300
+++ b/mercurial/changegroup.py	Fri Oct 09 14:59:37 2015 -0700
@@ -584,9 +584,9 @@
     _changegroupinfo(repo, csets, source)
     return bundler.generate(commonrevs, csets, fastpathlinkrev, source)
 
-def getsubset(repo, outgoing, bundler, source, fastpath=False, version='01'):
+def getsubset(repo, outgoing, bundler, source, fastpath=False):
     gengroup = getsubsetraw(repo, outgoing, bundler, source, fastpath)
-    return packermap[version][1](util.chunkbuffer(gengroup), None)
+    return packermap[bundler.version][1](util.chunkbuffer(gengroup), None)
 
 def changegroupsubset(repo, roots, heads, source, version='01'):
     """Compute a changegroup consisting of all the nodes that are
@@ -613,7 +613,7 @@
     discbases = [n for n in discbases if n not in included]
     outgoing = discovery.outgoing(cl, discbases, heads)
     bundler = packermap[version][0](repo)
-    return getsubset(repo, outgoing, bundler, source, version=version)
+    return getsubset(repo, outgoing, bundler, source)
 
 def getlocalchangegroupraw(repo, source, outgoing, bundlecaps=None,
                            version='01'):

--- a/tests/test-bundle-type.t	Mon Oct 12 15:42:32 2015 +0300
+++ b/tests/test-bundle-type.t	Fri Oct 09 14:59:37 2015 -0700
@@ -63,7 +63,7 @@
   1 changesets found
   HG20\x00\x00 (esc)
   Stream params: {}
-  changegroup -- "{'version': '01'}"
+  changegroup -- "{'version': '02'}"
       c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
   
   % test bundle type v2
@@ -71,7 +71,7 @@
   1 changesets found
   HG20\x00\x00 (esc)
   Stream params: {'Compression': 'BZ'}
-  changegroup -- "{'version': '01'}"
+  changegroup -- "{'version': '02'}"
       c35a0f9217e65d1fdb90c936ffa7dbe679f83ddf
   
   % test bundle type v1