view mercurial/discovery.py @ 13550:1792b8a9422b stable

merge: back out single-parent fast-forward merge

This backs out

 changeset:   13158:9e7e24052745
 user:        Mads Kiilerich <[e-mail]>
 date:        Tue Dec 07 03:29:21 2010 +0100
 summary:     merge: fast-forward merge with descendant

Before named branches, the invariants were:

a) "merges" always have two parents
b) p1 is not linearly related to p2

Adding named branches made (b) problematic, so the above patch was
introduced, which fixed (b) but broke (a).

After discussion, we decided that the invariants should be:

a) "merges" always have two parents
b) p1 is not linearly related to p2 OR p1 and p2 are on different branches

# discovery.py - protocol changeset discovery functions
#
# Copyright 2010 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from node import nullid, short
from i18n import _
import util, error

def findcommonincoming(repo, remote, heads=None, force=False):
    """Return a tuple (common, missing roots, heads) used to identify
    missing nodes from remote.

    If a list of heads is specified, return only nodes which are heads
    or ancestors of these heads.
    """
    m = repo.changelog.nodemap
    search = []
    fetch = set()
    seen = set()
    seenbranch = set()
    base = set()

    if not heads:
        heads = remote.heads()

    if repo.changelog.tip() == nullid:
        base.add(nullid)
        if heads != [nullid]:
            return [nullid], [nullid], list(heads)
        return [nullid], [], []

    # assume we're closer to the tip than the root
    # and start by examining the heads
    repo.ui.status(_("searching for changes\n"))

    unknown = []
    for h in heads:
        if h not in m:
            unknown.append(h)
        else:
            base.add(h)

    heads = unknown
    if not unknown:
        return list(base), [], []

    req = set(unknown)
    reqcnt = 0

    # search through remote branches
    # a 'branch' here is a linear segment of history, with four parts:
    # head, root, first parent, second parent
    # (a branch always has two parents (or none) by definition)
    unknown = remote.branches(unknown)
    while unknown:
        r = []
        while unknown:
            n = unknown.pop(0)
            if n[0] in seen:
                continue

            repo.ui.debug("examining %s:%s\n"
                          % (short(n[0]), short(n[1])))
            if n[0] == nullid: # found the end of the branch
                pass
            elif n in seenbranch:
                repo.ui.debug("branch already found\n")
                continue
            elif n[1] and n[1] in m: # do we know the base?
                repo.ui.debug("found incomplete branch %s:%s\n"
                              % (short(n[0]), short(n[1])))
                search.append(n[0:2]) # schedule branch range for scanning
                seenbranch.add(n)
            else:
                if n[1] not in seen and n[1] not in fetch:
                    if n[2] in m and n[3] in m:
                        repo.ui.debug("found new changeset %s\n" %
                                      short(n[1]))
                        fetch.add(n[1]) # earliest unknown
                    for p in n[2:4]:
                        if p in m:
                            base.add(p) # latest known

                for p in n[2:4]:
                    if p not in req and p not in m:
                        r.append(p)
                        req.add(p)
            seen.add(n[0])

        if r:
            reqcnt += 1
            repo.ui.progress(_('searching'), reqcnt, unit=_('queries'))
            repo.ui.debug("request %d: %s\n" %
                        (reqcnt, " ".join(map(short, r))))
            for p in xrange(0, len(r), 10):
                for b in remote.branches(r[p:p + 10]):
                    repo.ui.debug("received %s:%s\n" %
                                  (short(b[0]), short(b[1])))
                    unknown.append(b)

    # do binary search on the branches we found
    while search:
        newsearch = []
        reqcnt += 1
        repo.ui.progress(_('searching'), reqcnt, unit=_('queries'))
        for n, l in zip(search, remote.between(search)):
            l.append(n[1])
            p = n[0]
            f = 1
            for i in l:
                repo.ui.debug("narrowing %d:%d %s\n" % (f, len(l), short(i)))
                if i in m:
                    if f <= 2:
                        repo.ui.debug("found new branch changeset %s\n" %
                                          short(p))
                        fetch.add(p)
                        base.add(i)
                    else:
                        repo.ui.debug("narrowed branch search to %s:%s\n"
                                      % (short(p), short(i)))
                        newsearch.append((p, i))
                    break
                p, f = i, f * 2
            search = newsearch

    # sanity check our fetch list
    for f in fetch:
        if f in m:
            raise error.RepoError(_("already have changeset ")
                                  + short(f[:4]))

    base = list(base)
    if base == [nullid]:
        if force:
            repo.ui.warn(_("warning: repository is unrelated\n"))
        else:
            raise util.Abort(_("repository is unrelated"))

    repo.ui.debug("found new changesets starting at " +
                 " ".join([short(f) for f in fetch]) + "\n")

    repo.ui.progress(_('searching'), None)
    repo.ui.debug("%d total queries\n" % reqcnt)

    return base, list(fetch), heads

def findoutgoing(repo, remote, base=None, remoteheads=None, force=False):
    """Return list of nodes that are roots of subsets not in remote

    If base dict is specified, assume that these nodes and their parents
    exist on the remote side.
    If remotehead is specified, assume it is the list of the heads from
    the remote repository.
    """
    if base is None:
        base = findcommonincoming(repo, remote, heads=remoteheads,
                                  force=force)[0]
    else:
        base = list(base)

    repo.ui.debug("common changesets up to "
                  + " ".join(map(short, base)) + "\n")

    remain = set(repo.changelog.nodemap)

    # prune everything remote has from the tree
    remain.remove(nullid)
    remove = base
    while remove:
        n = remove.pop(0)
        if n in remain:
            remain.remove(n)
            for p in repo.changelog.parents(n):
                remove.append(p)

    # find every node whose parents have been pruned
    subset = []
    # find every remote head that will get new children
    for n in remain:
        p1, p2 = repo.changelog.parents(n)
        if p1 not in remain and p2 not in remain:
            subset.append(n)

    return subset

def prepush(repo, remote, force, revs, newbranch):
    '''Analyze the local and remote repositories and determine which
    changesets need to be pushed to the remote. Return value depends
    on circumstances:

    If we are not going to push anything, return a tuple (None,
    outgoing) where outgoing is 0 if there are no outgoing
    changesets and 1 if there are, but we refuse to push them
    (e.g. would create new remote heads).

    Otherwise, return a tuple (changegroup, remoteheads), where
    changegroup is a readable file-like object whose read() returns
    successive changegroup chunks ready to be sent over the wire and
    remoteheads is the list of remote heads.'''
    remoteheads = remote.heads()
    common, inc, rheads = findcommonincoming(repo, remote, heads=remoteheads,
                                             force=force)

    cl = repo.changelog
    update = findoutgoing(repo, remote, common, remoteheads)
    outg, bases, heads = cl.nodesbetween(update, revs)

    if not bases:
        repo.ui.status(_("no changes found\n"))
        return None, 1

    if not force and remoteheads != [nullid]:
        if remote.capable('branchmap'):
            # Check for each named branch if we're creating new remote heads.
            # To be a remote head after push, node must be either:
            # - unknown locally
            # - a local outgoing head descended from update
            # - a remote head that's known locally and not
            #   ancestral to an outgoing head

            # 1. Create set of branches involved in the push.
            branches = set(repo[n].branch() for n in outg)

            # 2. Check for new branches on the remote.
            remotemap = remote.branchmap()
            newbranches = branches - set(remotemap)
            if newbranches and not newbranch: # new branch requires --new-branch
                branchnames = ', '.join(sorted(newbranches))
                raise util.Abort(_("push creates new remote branches: %s!")
                                   % branchnames,
                                 hint=_("use 'hg push --new-branch' to create"
                                        " new remote branches"))
            branches.difference_update(newbranches)

            # 3. Construct the initial oldmap and newmap dicts.
            # They contain information about the remote heads before and
            # after the push, respectively.
            # Heads not found locally are not included in either dict,
            # since they won't be affected by the push.
            # unsynced contains all branches with incoming changesets.
            oldmap = {}
            newmap = {}
            unsynced = set()
            for branch in branches:
                remotebrheads = remotemap[branch]
                prunedbrheads = [h for h in remotebrheads if h in cl.nodemap]
                oldmap[branch] = prunedbrheads
                newmap[branch] = list(prunedbrheads)
                if len(remotebrheads) > len(prunedbrheads):
                    unsynced.add(branch)

            # 4. Update newmap with outgoing changes.
            # This will possibly add new heads and remove existing ones.
            ctxgen = (repo[n] for n in outg)
            repo._updatebranchcache(newmap, ctxgen)

        else:
            # 1-4b. old servers: Check for new topological heads.
            # Construct {old,new}map with branch = None (topological branch).
            # (code based on _updatebranchcache)
            oldheads = set(h for h in remoteheads if h in cl.nodemap)
            newheads = oldheads.union(outg)
            if len(newheads) > 1:
                for latest in reversed(outg):
                    if latest not in newheads:
                        continue
                    minhrev = min(cl.rev(h) for h in newheads)
                    reachable = cl.reachable(latest, cl.node(minhrev))
                    reachable.remove(latest)
                    newheads.difference_update(reachable)
            branches = set([None])
            newmap = {None: newheads}
            oldmap = {None: oldheads}
            unsynced = inc and branches or set()

        # 5. Check for new heads.
        # If there are more heads after the push than before, a suitable
        # error message, depending on unsynced status, is displayed.
        error = None
        for branch in branches:
            newhs = set(newmap[branch])
            oldhs = set(oldmap[branch])
            if len(newhs) > len(oldhs):
                if error is None:
                    if branch:
                        error = _("push creates new remote heads "
                                  "on branch '%s'!") % branch
                    else:
                        error = _("push creates new remote heads!")
                    if branch in unsynced:
                        hint = _("you should pull and merge or "
                                 "use push -f to force")
                    else:
                        hint = _("did you forget to merge? "
                                 "use push -f to force")
                if branch:
                    repo.ui.debug("new remote heads on branch '%s'\n" % branch)
                for h in (newhs - oldhs):
                    repo.ui.debug("new remote head %s\n" % short(h))
        if error:
            raise util.Abort(error, hint=hint)

        # 6. Check for unsynced changes on involved branches.
        if unsynced:
            repo.ui.warn(_("note: unsynced remote changes!\n"))

    if revs is None:
        # use the fast path, no race possible on push
        nodes = repo.changelog.findmissing(common)
        cg = repo._changegroup(nodes, 'push')
    else:
        cg = repo.changegroupsubset(update, revs, 'push')
    return cg, remoteheads