tests/bundles/test-revlog-diff-relative-to-nullrev.sh

emitrevision: if we need to compute a delta on the fly, try p1 or p2 first

Falling back to `prev` does not yield any real value on modern storage and
result in pathological changes to be created on the other side. Doing a delta
against a parent will likely be smaller (helping the network) and will be safer
to apply on the client (helping future pulls by Triggering intermediate
snapshop where they will be needed by later deltas).

#!/bin/bash
#
# Make sure to patch mercurial to create the delta against nullrev
#
# # Parent  cdb85d0512b81031d4a7b30d6a5ddbe69ef1a876
#
# diff --git a/mercurial/revlogutils/deltas.py b/mercurial/revlogutils/deltas.py
# --- a/mercurial/revlogutils/deltas.py
# +++ b/mercurial/revlogutils/deltas.py
# @@ -1117,7 +1117,10 @@ class deltacomputer:
#                  candidaterevs = next(groups)
#
#          if deltainfo is None:
# -            deltainfo = self._fullsnapshotinfo(fh, revinfo, target_rev)
# +            if revlog._generaldelta:
# +                deltainfo = self._builddeltainfo(revinfo, nullrev, fh)
# +            else:
# +                deltainfo = self._fullsnapshotinfo(fh, revinfo, target_rev)


cd "`dirname \"$0\"`"
export HGRCPATH=
export HGMODULEPOLICY=py

rm -rf nullrev-diff
../../hg init nullrev-diff  --config format.revlog-compression=zlib
cd nullrev-diff
echo hi > a
../../../hg commit -Am root-B
echo ho > a
../../../hg commit -Am child-A
hg up null
echo ha > a
../../../hg commit -Am root-A
../../../hg debugdeltachain a
rm -rf .hg/cache/ .hg/wcache/
cd ..

tar cf test-revlog-diff-relative-to-nullrev.tar nullrev-diff

rm -rf nullrev-diff