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addrevision: rework generaldelta computation

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The old code have multiple explicit tests and code duplications. This makes it
hard to improve the code. We rewrite the logic in a more generic way, not
changing anything of the computed result.

The final goal here is to eventually be able to:

- factor out the default fallback case "try against 'prev'" in a single place

- allow 'lazydeltabase' case to use the smarter general delta code path when
  the incoming base does not provide us with a good delta.
This commit is contained in:
Pierre-Yves David 2015-12-01 18:45:16 -08:00
parent b35ce782e0
commit 01dc52b10b
1 changed files with 14 additions and 25 deletions
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39
mercurial/revlog.py
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@ -1434,34 +1434,23 @@ class revlog(object):
# Try against prev to hopefully save us a fulltext.
delta = builddelta(prev)
elif self._generaldelta:
if p2r != nullrev and self._aggressivemergedeltas:
delta = builddelta(p1r)
delta2 = builddelta(p2r)
p1good = self._isgooddelta(delta, textlen)
p2good = self._isgooddelta(delta2, textlen)
if p1good and p2good:
# If both are good deltas, choose the smallest
if delta2[1] < delta[1]:
delta = delta2
elif p2good:
# If only p2 is good, use it
delta = delta2
elif p1good:
pass
else:
# Neither is good, try against prev to hopefully save us
# a fulltext.
delta = builddelta(prev)
else:
parents = [p1r, p2r]
if not self._aggressivemergedeltas:
# Pick whichever parent is closer to us (to minimize the
# chance of having to build a fulltext). Since
# nullrev == -1, any non-merge commit will always pick p1r.
drev = p2r if p2r > p1r else p1r
delta = builddelta(drev)
# If the chosen delta will result in us making a full text,
# give it one last try against prev.
if drev != prev and not self._isgooddelta(delta, textlen):
delta = builddelta(prev)
parents = [max(parents)]
pdeltas = []
for p in parents:
pd = builddelta(p)
if self._isgooddelta(pd, textlen):
pdeltas.append(pd)
if pdeltas:
delta = min(pdeltas, key=lambda x: x[1])
elif prev not in parents:
# Neither is good, try against prev to hopefully save us
# a fulltext.
delta = builddelta(prev)
else:
delta = builddelta(prev)
if delta is not None: