diff --git a/mercurial/changegroup.py b/mercurial/changegroup.py
--- a/mercurial/changegroup.py
+++ b/mercurial/changegroup.py
@@ -245,7 +245,8 @@
         # no new manifest will be created and the manifest group will
         # be empty during the pull
         self.manifestheader()
-        repo.manifestlog._revlog.addgroup(self, revmap, trp)
+        deltas = self.deltaiter(revmap)
+        repo.manifestlog._revlog.addgroup(deltas, trp)
         repo.ui.progress(_('manifests'), None)
         self.callback = None
 
@@ -307,7 +308,8 @@
                 efiles.update(cl.readfiles(node))
 
             self.changelogheader()
-            cgnodes = cl.addgroup(self, csmap, trp, addrevisioncb=onchangelog)
+            deltas = self.deltaiter(csmap)
+            cgnodes = cl.addgroup(deltas, trp, addrevisioncb=onchangelog)
             efiles = len(efiles)
 
             if not cgnodes:
@@ -428,6 +430,27 @@
             ret = deltaheads + 1
         return ret
 
+    def deltaiter(self, linkmapper):
+        """
+        returns an iterator of the deltas in this changegroup
+
+        Useful for passing to the underlying storage system to be stored.
+        """
+        chain = None
+        for chunkdata in iter(lambda: self.deltachunk(chain), {}):
+            node = chunkdata['node']
+            p1 = chunkdata['p1']
+            p2 = chunkdata['p2']
+            cs = chunkdata['cs']
+            deltabase = chunkdata['deltabase']
+            delta = chunkdata['delta']
+            flags = chunkdata['flags']
+
+            link = linkmapper(cs)
+            chain = node
+
+            yield (node, p1, p2, link, deltabase, delta, flags)
+
 class cg2unpacker(cg1unpacker):
     """Unpacker for cg2 streams.
 
@@ -468,7 +491,8 @@
             d = chunkdata["filename"]
             repo.ui.debug("adding %s revisions\n" % d)
             dirlog = repo.manifestlog._revlog.dirlog(d)
-            if not dirlog.addgroup(self, revmap, trp):
+            deltas = self.deltaiter(revmap)
+            if not dirlog.addgroup(deltas, trp):
                 raise error.Abort(_("received dir revlog group is empty"))
 
 class headerlessfixup(object):
@@ -949,7 +973,8 @@
         fl = repo.file(f)
         o = len(fl)
         try:
-            if not fl.addgroup(source, revmap, trp):
+            deltas = source.deltaiter(revmap)
+            if not fl.addgroup(deltas, trp):
                 raise error.Abort(_("received file revlog group is empty"))
         except error.CensoredBaseError as e:
             raise error.Abort(_("received delta base is censored: %s") % e)
diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -1872,7 +1872,7 @@
             ifh.write(data[1])
             self.checkinlinesize(transaction, ifh)
 
-    def addgroup(self, cg, linkmapper, transaction, addrevisioncb=None):
+    def addgroup(self, deltas, transaction, addrevisioncb=None):
         """
         add a delta group
 
@@ -1905,20 +1905,12 @@
             ifh.flush()
         try:
             # loop through our set of deltas
-            chain = None
-            for chunkdata in iter(lambda: cg.deltachunk(chain), {}):
-                node = chunkdata['node']
-                p1 = chunkdata['p1']
-                p2 = chunkdata['p2']
-                cs = chunkdata['cs']
-                deltabase = chunkdata['deltabase']
-                delta = chunkdata['delta']
-                flags = chunkdata['flags'] or REVIDX_DEFAULT_FLAGS
+            for data in deltas:
+                node, p1, p2, link, deltabase, delta, flags = data
+                flags = flags or REVIDX_DEFAULT_FLAGS
 
                 nodes.append(node)
-                chain = node
 
-                link = linkmapper(cs)
                 if node in self.nodemap:
                     # this can happen if two branches make the same change
                     continue
diff --git a/tests/test-revlog-raw.py b/tests/test-revlog-raw.py
--- a/tests/test-revlog-raw.py
+++ b/tests/test-revlog-raw.py
@@ -119,11 +119,28 @@
                     'deltabase': rlog.node(deltaparent),
                     'delta': rlog.revdiff(deltaparent, r)}
 
+        def deltaiter(self, linkmapper):
+            chain = None
+            for chunkdata in iter(lambda: self.deltachunk(chain), {}):
+                node = chunkdata['node']
+                p1 = chunkdata['p1']
+                p2 = chunkdata['p2']
+                cs = chunkdata['cs']
+                deltabase = chunkdata['deltabase']
+                delta = chunkdata['delta']
+                flags = chunkdata['flags']
+
+                link = linkmapper(cs)
+                chain = node
+
+                yield (node, p1, p2, link, deltabase, delta, flags)
+
     def linkmap(lnode):
         return rlog.rev(lnode)
 
     dlog = newrevlog(destname, recreate=True)
-    dlog.addgroup(dummychangegroup(), linkmap, tr)
+    dummydeltas = dummychangegroup().deltaiter(linkmap)
+    dlog.addgroup(dummydeltas, tr)
     return dlog
 
 def lowlevelcopy(rlog, tr, destname=b'_destrevlog.i'):