D522: revlog: abort on attempt to write null revision

[martinvonz (Martin von Zweigbergk)]

martinvonz created this revision.
Herald added a reviewer: indygreg.
Herald added a subscriber: mercurial-devel.
Herald added a reviewer: hg-reviewers.

REVISION SUMMARY
  My repo got corrupted yesterday by something that ended up writing the
  null revision to the revlog (nullid hash, not nullrev index, of
  course).  We use many extensions internally (narrowhg, remotefilelog,
  evolve, internal extensions) and treemanifests are on. The null
  revision was written to the changelog, the root manifest log, and one
  subdirectory manifest log. I have no idea exactly why the null
  revision was written, but it seems cheap enough to check that we
  should fail instead of corrupting the repo.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D522

AFFECTED FILES
  mercurial/revlog.py

CHANGE DETAILS

diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -1575,6 +1575,9 @@
         useful when reusing a revision not stored in this revlog (ex: received
         over wire, or read from an external bundle).
         """
+        if node == nullid:
+            raise RevlogError(_("%s: attempt to add null revision") %
+                              (self.indexfile))
         dfh = None
         if not self._inline:
             dfh = self.opener(self.datafile, "a+")



To: martinvonz, indygreg, #hg-reviewers
Cc: mercurial-devel