localrepo: move the _changegroupsubset method in changegroup module

This is a gratuitous code move aimed at reducing the localrepo bloatness.

The method had 3 callers total, far too few for being kept in local repo.

mercurial/changegroup.py

@@ -428,3 +428,20 b' class bundle10(object):'
     def builddeltaheader(self, node, p1n, p2n, basenode, linknode):
         # do nothing with basenode, it is implicitly the previous one in HG10
         return struct.pack(self.deltaheader, node, p1n, p2n, linknode)
+
+def getsubset(repo, outgoing, bundler, source, fastpath=False):
+    repo = repo.unfiltered()
+    commonrevs = outgoing.common
+    csets = outgoing.missing
+    heads = outgoing.missingheads
+    # We go through the fast path if we get told to, or if all (unfiltered
+    # heads have been requested (since we then know there all linkrevs will
+    # be pulled by the client).
+    heads.sort()
+    fastpathlinkrev = fastpath or (
+            repo.filtername is None and heads == sorted(repo.heads()))
+
+    repo.hook('preoutgoing', throw=True, source=source)
+    repo.changegroupinfo(csets, source)
+    gengroup = bundler.generate(commonrevs, csets, fastpathlinkrev, source)
+    return unbundle10(util.chunkbuffer(gengroup), 'UN')

mercurial/exchange.py

@@ -181,7 +181,8 b' def _pushchangeset(pushop):'
         # push everything,
         # use the fast path, no race possible on push
         bundler = changegroup.bundle10(pushop.repo, bundlecaps)
-        cg = pushop.repo._changegroupsubset(outgoing,
+        cg = changegroup.getsubset(pushop.repo,
+                                   outgoing,
                                             bundler,
                                             'push',
                                             fastpath=True)

mercurial/localrepo.py

@@ -1714,7 +1714,7 b' class localrepository(object):'
             discbases.extend([p for p in cl.parents(n) if p != nullid])
         outgoing = discovery.outgoing(cl, discbases, heads)
         bundler = changegroup.bundle10(self)
-        return self._changegroupsubset(outgoing, bundler, source)
+        return changegroup.getsubset(self, outgoing, bundler, source)
 
     def getlocalbundle(self, source, outgoing, bundlecaps=None):
         """Like getbundle, but taking a discovery.outgoing as an argument.
@@ -1724,7 +1724,7 b' class localrepository(object):'
         if not outgoing.missing:
             return None
         bundler = changegroup.bundle10(self, bundlecaps)
-        return self._changegroupsubset(outgoing, bundler, source)
+        return changegroup.getsubset(self, outgoing, bundler, source)
 
     def getbundle(self, source, heads=None, common=None, bundlecaps=None):
         """Like changegroupsubset, but returns the set difference between the
@@ -1747,24 +1747,6 b' class localrepository(object):'
                                    discovery.outgoing(cl, common, heads),
                                    bundlecaps=bundlecaps)
 
-    @unfilteredmethod
-    def _changegroupsubset(self, outgoing, bundler, source,
-                           fastpath=False):
-        commonrevs = outgoing.common
-        csets = outgoing.missing
-        heads = outgoing.missingheads
-        # We go through the fast path if we get told to, or if all (unfiltered
-        # heads have been requested (since we then know there all linkrevs will
-        # be pulled by the client).
-        heads.sort()
-        fastpathlinkrev = fastpath or (
-                self.filtername is None and heads == sorted(self.heads()))
-
-        self.hook('preoutgoing', throw=True, source=source)
-        self.changegroupinfo(csets, source)
-        gengroup = bundler.generate(commonrevs, csets, fastpathlinkrev, source)
-        return changegroup.unbundle10(util.chunkbuffer(gengroup), 'UN')
-
     def changegroup(self, basenodes, source):
         # to avoid a race we use changegroupsubset() (issue1320)
         return self.changegroupsubset(basenodes, self.heads(), source)