revlogv2: temporarily forbid inline revlogs

See inline comments. I plan to fix the underlying issue before revlogv2 is
stabilized.

Differential Revision: https://phab.mercurial-scm.org/D10030

mercurial/revlog.py

@@ -639,7 +639,11 b' class revlog(object):'
                     % (flags >> 16, fmt, self.indexfile)
                 )
 
-            self._inline = versionflags & FLAG_INLINE_DATA
+            # There is a bug in the transaction handling when going from an
+            # inline revlog to a separate index and data file. Turn it off until
+            # it's fixed, since v2 revlogs sometimes get rewritten on exchange.
+            # See issue6485
+            self._inline = False
             # generaldelta implied by version 2 revlogs.
             self._generaldelta = True