# HG changeset patch
# User Boris Feld <boris.feld@octobus.net>
# Date 2018-10-31 10:02:08
# Node ID bafa1c4bb7a8d397f62e0cd75b8064ef1375b753
# Parent  588f1e9a4d1665b8dc02ab409312f59d06414d02

sparse-revlog: only refine delta candidates in the sparse case (issue6006)

Starting with 5aef5afa8654, a valid delta parent might be "refined". This
allows repository using sparse-revlog to produce better delta chain by using
better intermediate snapshot base.

However, this refining step was performed in all cases, including for
repository not using sparse-revlog. This could produce a strange chain in the
general delta case and corrupted repository in the non-general delta case.

We now skip this step unless sparse-revlog is in use.

In issue 6006, Yuya Nishihara provided a test case using an external
repository, so we did not include it. Finding "laboratory" condition to
reproduce this case and implementing an efficient test reproducing it is a bit
tricky. We do not foresee to have the time to provide one by the release date.

Differential Revision: https://phab.mercurial-scm.org/D5197

diff --git a/mercurial/revlogutils/deltas.py b/mercurial/revlogutils/deltas.py
--- a/mercurial/revlogutils/deltas.py
+++ b/mercurial/revlogutils/deltas.py
@@ -646,6 +646,11 @@ def _refinedgroups(revlog, p1, p2, cache
         if good is not None:
             break
 
+    # If sparse revlog is enabled, we can try to refine the available deltas
+    if not revlog._sparserevlog:
+        yield None
+        return
+
     # if we have a refinable value, try to refine it
     if good is not None and good not in (p1, p2) and revlog.issnapshot(good):
         # refine snapshot down