revlog: add a `get_revlog` method

This might seen weird, but I actually thing we have been needing this for a
long time. There is multiple object that kind of pretend being revlogs while
actually wrapping the actual revlog. Since multiple code needs to access the
actuel revlog. See documentation for more details.

Expect cleanup of various places one the current series is done.

mercurial/filelog.py

@@ -42,6 +42,15 b' class filelog:'
         opts = opener.options
         self._fix_issue6528 = opts.get(b'issue6528.fix-incoming', True)
 
+    def get_revlog(self):
+        """return an actual revlog instance if any
+
+        This exist because a lot of code leverage the fact the underlying
+        storage is a revlog for optimization, so giving simple way to access
+        the revlog instance helps such code.
+        """
+        return self._revlog
+
     def __len__(self):
         return len(self._revlog)
 

mercurial/interfaces/repository.py

@@ -1404,6 +1404,14 b' class imanifeststorage(interfaceutil.Int'
         This one behaves the same way, except for manifest data.
         """
 
+    def get_revlog():
+        """return an actual revlog instance if any
+
+        This exist because a lot of code leverage the fact the underlying
+        storage is a revlog for optimization, so giving simple way to access
+        the revlog instance helps such code.
+        """
+
 
 class imanifestlog(interfaceutil.Interface):
     """Interface representing a collection of manifest snapshots.

mercurial/manifest.py

@@ -1617,6 +1617,15 b' class manifestrevlog:'
         self.index = self._revlog.index
         self._generaldelta = self._revlog._generaldelta
 
+    def get_revlog(self):
+        """return an actual revlog instance if any
+
+        This exist because a lot of code leverage the fact the underlying
+        storage is a revlog for optimization, so giving simple way to access
+        the revlog instance helps such code.
+        """
+        return self._revlog
+
     def _setupmanifestcachehooks(self, repo):
         """Persist the manifestfulltextcache on lock release"""
         if not util.safehasattr(repo, '_wlockref'):

mercurial/revlog.py

@@ -663,6 +663,10 b' class revlog:'
         # revlog header -> revlog compressor
         self._decompressors = {}
 
+    def get_revlog(self):
+        """simple function to mirror API of other not-really-revlog API"""
+        return self
+
     @util.propertycache
     def revlog_kind(self):
         return self.target[0]