contrib/undumprevlog

snapshot: fix line order when skipping over empty deltas

The code movement in 37957e07138c introduced an error.

Since 8f83a953dddf, we discarded some revisions because they are identical to
their delta base (and use that delta base instead). That logic is good,
however, in 37957e07138c we mixed up the order of two line, adding the "new"
revision to the set of already tested one, instead of the discarded one. So in
practice, we were never investigating any revisions in a chain starting with
an empty delta. Creating significantly worst delta chain (eg: Mercurial's
manifest move goes from about 60MB up to about 80MB).

#!/usr/bin/env python
# Undump a dump from dumprevlog
# $ hg init
# $ undumprevlog < repo.dump

from __future__ import absolute_import, print_function

import sys
from mercurial import (
    node,
    revlog,
    transaction,
    vfs as vfsmod,
)
from mercurial.utils import (
    procutil,
)

for fp in (sys.stdin, sys.stdout, sys.stderr):
    procutil.setbinary(fp)

opener = vfsmod.vfs('.', False)
tr = transaction.transaction(sys.stderr.write, opener, {'store': opener},
                             "undump.journal")
while True:
    l = sys.stdin.readline()
    if not l:
        break
    if l.startswith("file:"):
        f = l[6:-1]
        r = revlog.revlog(opener, f)
        print(f)
    elif l.startswith("node:"):
        n = node.bin(l[6:-1])
    elif l.startswith("linkrev:"):
        lr = int(l[9:-1])
    elif l.startswith("parents:"):
        p = l[9:-1].split()
        p1 = node.bin(p[0])
        p2 = node.bin(p[1])
    elif l.startswith("length:"):
        length = int(l[8:-1])
        sys.stdin.readline() # start marker
        d = sys.stdin.read(length)
        sys.stdin.readline() # end marker
        r.addrevision(d, tr, lr, p1, p2)

tr.close()