bundlerevlog: extract 'baserevision' method

This makes possible to use bundlerevlog class with subclasses of revlog
that override revlog's 'revision' method. In particular this change is necessary
to implement manifest compression, as it allows extension to replace manifest
class and override 'revision' method there.

mercurial/bundlerepo.py

@@ -120,7 +120,7 b' class bundlerevlog(revlog.revlog):'
             chain.append(iterrev)
             iterrev = self.index[iterrev][3]
         if text is None:
-            text = revlog.revlog.revision(self, iterrev)
+            text = self.baserevision(iterrev)
 
         while chain:
             delta = self._chunk(chain.pop())
@@ -130,6 +130,12 b' class bundlerevlog(revlog.revlog):'
         self._cache = (node, rev, text)
         return text
 
+    def baserevision(self, nodeorrev):
+        # Revlog subclasses may override 'revision' method to modify format of
+        # content retrieved from revlog. To use bundlerevlog with such class one
+        # needs to override 'baserevision' and make more specific call here.
+        return revlog.revlog.revision(self, nodeorrev)
+
     def addrevision(self, text, transaction, link, p1=None, p2=None, d=None):
         raise NotImplementedError
     def addgroup(self, revs, linkmapper, transaction):
@@ -146,12 +152,21 b' class bundlechangelog(bundlerevlog, chan'
         bundlerevlog.__init__(self, opener, self.indexfile, bundle,
                               linkmapper)
 
+    def baserevision(self, nodeorrev):
+        # Although changelog doesn't override 'revision' method, some extensions
+        # may replace this class with another that does. Same story with
+        # manifest and filelog classes.
+        return changelog.changelog.revision(self, nodeorrev)
+
 class bundlemanifest(bundlerevlog, manifest.manifest):
     def __init__(self, opener, bundle, linkmapper):
         manifest.manifest.__init__(self, opener)
         bundlerevlog.__init__(self, opener, self.indexfile, bundle,
                               linkmapper)
 
+    def baserevision(self, nodeorrev):
+        return manifest.manifest.revision(self, nodeorrev)
+
 class bundlefilelog(bundlerevlog, filelog.filelog):
     def __init__(self, opener, path, bundle, linkmapper, repo):
         filelog.filelog.__init__(self, opener, path)
@@ -159,6 +174,9 b' class bundlefilelog(bundlerevlog, filelo'
                               linkmapper)
         self._repo = repo
 
+    def baserevision(self, nodeorrev):
+        return filelog.filelog.revision(self, nodeorrev)
+
     def _file(self, f):
         self._repo.file(f)