revlog: make sure we never use sparserevlog without general delta (issue6056) We are getting user report where the delta code tries to use `sparse-revlog` logic on repository where `generaldelta` is disabled. This can't work so we ensure the two booleans have a consistent value. Creating this kind of repository is not expected to be possible the current bug report point at a clonebundle related bug that is still to be properly isolated (Yuya Nishihara seems to a have done it). Corrupting a repository to reproduce the issue is possible. A test using this method is included in this fix.

--- a/mercurial/revlog.py	Wed Jan 30 18:15:38 2019 +0100
+++ b/mercurial/revlog.py	Thu Jan 24 18:22:47 2019 -0500
@@ -497,6 +497,9 @@
         else:
             raise error.RevlogError(_('unknown version (%d) in revlog %s') %
                                     (fmt, self.indexfile))
+        # sparse-revlog can't be on without general-delta (issue6056)
+        if not self._generaldelta:
+            self._sparserevlog = False
 
         self._storedeltachains = True