mercurial/repair.py

strip: calculate list of extra nodes to save and pass it to changegroupsubset

When we remove revision N from the repository, all revisions >= N are
affected: either it's a descendant from N and will also be removed, or
it's not a descendant of N and will be renumbered.

As a consequence, we have to (at least temporarily) remove all filelog
and manifest revisions that have a linkrev >= N, readding some of them
later.

Unfortunately, it's possible to have a revlog with two revisions
r1 and r2 such that r1 < r2, but linkrev(r1) > linkrev(r2).  If we try
to strip revision linkrev(r1) from the repository, we'll also lose
revision r2 when we truncate this revlog.

We already use changegroupsubset to create a temporary changegroup
containing the revisions that have to be restored, but that function is
unable to detect that we also wanted to save the r2 in the case above.

So we manually calculate these extra nodes and pass it to changegroupsubset.

This should fix issue764.

# repair.py - functions for repository repair for mercurial
#
# Copyright 2005, 2006 Chris Mason <[e-mail]>
# Copyright 2007 Matt Mackall
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

import changegroup, os
from node import *

def _limitheads(cl, stoprev):
    """return the list of all revs >= stoprev that have no children"""
    seen = {}
    heads = []

    for r in xrange(cl.count() - 1, stoprev - 1, -1):
        if r not in seen:
            heads.append(r)
        for p in cl.parentrevs(r):
            seen[p] = 1
    return heads

def _bundle(repo, bases, heads, node, suffix, extranodes=None):
    """create a bundle with the specified revisions as a backup"""
    cg = repo.changegroupsubset(bases, heads, 'strip', extranodes)
    backupdir = repo.join("strip-backup")
    if not os.path.isdir(backupdir):
        os.mkdir(backupdir)
    name = os.path.join(backupdir, "%s-%s" % (short(node), suffix))
    repo.ui.warn("saving bundle to %s\n" % name)
    return changegroup.writebundle(cg, name, "HG10BZ")

def _collectfilenodes(repo, striprev):
    """find out the first node that should be stripped from each filelog"""
    mm = repo.changectx(striprev).manifest()
    filenodes = {}

    for x in xrange(striprev, repo.changelog.count()):
        for name in repo.changectx(x).files():
            if name in filenodes:
                continue
            filenodes[name] = mm.get(name)

    return filenodes

def _collectextranodes(repo, files, link):
    """return the nodes that have to be saved before the strip"""
    def collectone(revlog):
        extra = []
        startrev = count = revlog.count()
        # find the truncation point of the revlog
        for i in xrange(0, count):
            node = revlog.node(i)
            lrev = revlog.linkrev(node)
            if lrev >= link:
                startrev = i + 1
                break

        # see if any revision after that point has a linkrev less than link
        # (we have to manually save these guys)
        for i in xrange(startrev, count):
            node = revlog.node(i)
            lrev = revlog.linkrev(node)
            if lrev < link:
                extra.append((node, cl.node(lrev)))

        return extra

    extranodes = {}
    cl = repo.changelog
    extra = collectone(repo.manifest)
    if extra:
        extranodes[1] = extra
    for fname in files:
        f = repo.file(fname)
        extra = collectone(f)
        if extra:
            extranodes[fname] = extra

    return extranodes

def _stripall(repo, striprev, filenodes):
    """strip the requested nodes from the filelogs"""
    # we go in two steps here so the strip loop happens in a
    # sensible order.  When stripping many files, this helps keep
    # our disk access patterns under control.

    files = filenodes.keys()
    files.sort()
    for name in files:
        f = repo.file(name)
        fnode = filenodes[name]
        frev = 0
        if fnode is not None and fnode in f.nodemap:
            frev = f.rev(fnode)
        f.strip(frev, striprev)

def strip(ui, repo, node, backup="all"):
    cl = repo.changelog
    # TODO delete the undo files, and handle undo of merge sets
    pp = cl.parents(node)
    striprev = cl.rev(node)

    # save is a list of all the branches we are truncating away
    # that we actually want to keep.  changegroup will be used
    # to preserve them and add them back after the truncate
    saveheads = []
    savebases = {}

    heads = [cl.node(r) for r in _limitheads(cl, striprev)]
    seen = {}

    # search through all the heads, finding those where the revision
    # we want to strip away is an ancestor.  Also look for merges
    # that might be turned into new heads by the strip.
    while heads:
        h = heads.pop()
        n = h
        while True:
            seen[n] = 1
            pp = cl.parents(n)
            if pp[1] != nullid:
                for p in pp:
                    if cl.rev(p) > striprev and p not in seen:
                        heads.append(p)
            if pp[0] == nullid:
                break
            if cl.rev(pp[0]) < striprev:
                break
            n = pp[0]
            if n == node:
                break
        r = cl.reachable(h, node)
        if node not in r:
            saveheads.append(h)
            for x in r:
                if cl.rev(x) > striprev:
                    savebases[x] = 1

    filenodes = _collectfilenodes(repo, striprev)

    extranodes = _collectextranodes(repo, filenodes, striprev)

    # create a changegroup for all the branches we need to keep
    if backup == "all":
        _bundle(repo, [node], cl.heads(), node, 'backup')
    if saveheads or extranodes:
        chgrpfile = _bundle(repo, savebases.keys(), saveheads, node, 'temp',
                            extranodes)

    _stripall(repo, striprev, filenodes)

    change = cl.read(node)
    cl.strip(striprev, striprev)
    repo.manifest.strip(repo.manifest.rev(change[0]), striprev)
    if saveheads or extranodes:
        ui.status("adding branch\n")
        f = open(chgrpfile, "rb")
        gen = changegroup.readbundle(f, chgrpfile)
        repo.addchangegroup(gen, 'strip', 'bundle:' + chgrpfile, True)
        f.close()
        if backup != "strip":
            os.unlink(chgrpfile)