view mercurial/discovery.py @ 31793:69d8fcf20014

help: document bundle specifications

I softly formalized the concept of a "bundle specification" a while
ago when I was working on clone bundles and stream clone bundles and
wanted a more robust way to define what exactly is in a bundle file.

The concept has existed for a while. Since it is part of the clone
bundles feature and exposed to the user via the "-t" argument to
`hg bundle`, it is something we need to support for the long haul.

After the 4.1 release, I heard a few people comment that they didn't
realize you could generate zstd bundles with `hg bundle`. I'm
partially to blame for not documenting it in bundle's docstring.

Additionally, I added a hacky, experimental feature for controlling
the compression level of bundles in 76104a4899ad. As the commit
message says, I went with a quick and dirty solution out of time
constraints. Furthermore, I wanted to eventually store this
configuration in the "bundlespec" so it could be made more flexible.

Given:

a) bundlespecs are here to stay
b) we don't have great documentation over what they are, despite being
   a user-facing feature
c) the list of available compression engines and their behavior isn't
   exposed
d) we need an extensible place to modify behavior of compression
   engines

I want to move forward with formalizing bundlespecs as a user-facing
feature. This commit does that by introducing a "bundlespec" help
page. Leaning on the just-added compression engine documentation
and API, the topic also conveniently lists available compression
engines and details about them. This makes features like zstd
bundle compression more discoverable. e.g. you can now
`hg help -k zstd` and it lists the "bundlespec" topic.

# 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 __future__ import absolute_import

from .i18n import _
from .node import (
    nullid,
    short,
)

from . import (
    bookmarks,
    branchmap,
    error,
    obsolete,
    phases,
    setdiscovery,
    treediscovery,
    util,
)

def findcommonincoming(repo, remote, heads=None, force=False):
    """Return a tuple (common, anyincoming, heads) used to identify the common
    subset of nodes between repo and remote.

    "common" is a list of (at least) the heads of the common subset.
    "anyincoming" is testable as a boolean indicating if any nodes are missing
      locally. If remote does not support getbundle, this actually is a list of
      roots of the nodes that would be incoming, to be supplied to
      changegroupsubset. No code except for pull should be relying on this fact
      any longer.
    "heads" is either the supplied heads, or else the remote's heads.

    If you pass heads and they are all known locally, the response lists just
    these heads in "common" and in "heads".

    Please use findcommonoutgoing to compute the set of outgoing nodes to give
    extensions a good hook into outgoing.
    """

    if not remote.capable('getbundle'):
        return treediscovery.findcommonincoming(repo, remote, heads, force)

    if heads:
        allknown = True
        knownnode = repo.changelog.hasnode # no nodemap until it is filtered
        for h in heads:
            if not knownnode(h):
                allknown = False
                break
        if allknown:
            return (heads, False, heads)

    res = setdiscovery.findcommonheads(repo.ui, repo, remote,
                                       abortwhenunrelated=not force)
    common, anyinc, srvheads = res
    return (list(common), anyinc, heads or list(srvheads))

class outgoing(object):
    '''Represents the set of nodes present in a local repo but not in a
    (possibly) remote one.

    Members:

      missing is a list of all nodes present in local but not in remote.
      common is a list of all nodes shared between the two repos.
      excluded is the list of missing changeset that shouldn't be sent remotely.
      missingheads is the list of heads of missing.
      commonheads is the list of heads of common.

    The sets are computed on demand from the heads, unless provided upfront
    by discovery.'''

    def __init__(self, repo, commonheads=None, missingheads=None,
                 missingroots=None):
        # at least one of them must not be set
        assert None in (commonheads, missingroots)
        cl = repo.changelog
        if missingheads is None:
            missingheads = cl.heads()
        if missingroots:
            discbases = []
            for n in missingroots:
                discbases.extend([p for p in cl.parents(n) if p != nullid])
            # TODO remove call to nodesbetween.
            # TODO populate attributes on outgoing instance instead of setting
            # discbases.
            csets, roots, heads = cl.nodesbetween(missingroots, missingheads)
            included = set(csets)
            missingheads = heads
            commonheads = [n for n in discbases if n not in included]
        elif not commonheads:
            commonheads = [nullid]
        self.commonheads = commonheads
        self.missingheads = missingheads
        self._revlog = cl
        self._common = None
        self._missing = None
        self.excluded = []

    def _computecommonmissing(self):
        sets = self._revlog.findcommonmissing(self.commonheads,
                                              self.missingheads)
        self._common, self._missing = sets

    @util.propertycache
    def common(self):
        if self._common is None:
            self._computecommonmissing()
        return self._common

    @util.propertycache
    def missing(self):
        if self._missing is None:
            self._computecommonmissing()
        return self._missing

def findcommonoutgoing(repo, other, onlyheads=None, force=False,
                       commoninc=None, portable=False):
    '''Return an outgoing instance to identify the nodes present in repo but
    not in other.

    If onlyheads is given, only nodes ancestral to nodes in onlyheads
    (inclusive) are included. If you already know the local repo's heads,
    passing them in onlyheads is faster than letting them be recomputed here.

    If commoninc is given, it must be the result of a prior call to
    findcommonincoming(repo, other, force) to avoid recomputing it here.

    If portable is given, compute more conservative common and missingheads,
    to make bundles created from the instance more portable.'''
    # declare an empty outgoing object to be filled later
    og = outgoing(repo, None, None)

    # get common set if not provided
    if commoninc is None:
        commoninc = findcommonincoming(repo, other, force=force)
    og.commonheads, _any, _hds = commoninc

    # compute outgoing
    mayexclude = (repo._phasecache.phaseroots[phases.secret] or repo.obsstore)
    if not mayexclude:
        og.missingheads = onlyheads or repo.heads()
    elif onlyheads is None:
        # use visible heads as it should be cached
        og.missingheads = repo.filtered("served").heads()
        og.excluded = [ctx.node() for ctx in repo.set('secret() or extinct()')]
    else:
        # compute common, missing and exclude secret stuff
        sets = repo.changelog.findcommonmissing(og.commonheads, onlyheads)
        og._common, allmissing = sets
        og._missing = missing = []
        og.excluded = excluded = []
        for node in allmissing:
            ctx = repo[node]
            if ctx.phase() >= phases.secret or ctx.extinct():
                excluded.append(node)
            else:
                missing.append(node)
        if len(missing) == len(allmissing):
            missingheads = onlyheads
        else: # update missing heads
            missingheads = phases.newheads(repo, onlyheads, excluded)
        og.missingheads = missingheads
    if portable:
        # recompute common and missingheads as if -r<rev> had been given for
        # each head of missing, and --base <rev> for each head of the proper
        # ancestors of missing
        og._computecommonmissing()
        cl = repo.changelog
        missingrevs = set(cl.rev(n) for n in og._missing)
        og._common = set(cl.ancestors(missingrevs)) - missingrevs
        commonheads = set(og.commonheads)
        og.missingheads = [h for h in og.missingheads if h not in commonheads]

    return og

def _headssummary(repo, remote, outgoing):
    """compute a summary of branch and heads status before and after push

    return {'branch': ([remoteheads], [newheads], [unsyncedheads])} mapping

    - branch: the branch name
    - remoteheads: the list of remote heads known locally
                   None if the branch is new
    - newheads: the new remote heads (known locally) with outgoing pushed
    - unsyncedheads: the list of remote heads unknown locally.
    """
    cl = repo.changelog
    headssum = {}
    # A. Create set of branches involved in the push.
    branches = set(repo[n].branch() for n in outgoing.missing)
    remotemap = remote.branchmap()
    newbranches = branches - set(remotemap)
    branches.difference_update(newbranches)

    # A. register remote heads
    remotebranches = set()
    for branch, heads in remote.branchmap().iteritems():
        remotebranches.add(branch)
        known = []
        unsynced = []
        knownnode = cl.hasnode # do not use nodemap until it is filtered
        for h in heads:
            if knownnode(h):
                known.append(h)
            else:
                unsynced.append(h)
        headssum[branch] = (known, list(known), unsynced)
    # B. add new branch data
    missingctx = list(repo[n] for n in outgoing.missing)
    touchedbranches = set()
    for ctx in missingctx:
        branch = ctx.branch()
        touchedbranches.add(branch)
        if branch not in headssum:
            headssum[branch] = (None, [], [])

    # C drop data about untouched branches:
    for branch in remotebranches - touchedbranches:
        del headssum[branch]

    # D. Update newmap with outgoing changes.
    # This will possibly add new heads and remove existing ones.
    newmap = branchmap.branchcache((branch, heads[1])
                                 for branch, heads in headssum.iteritems()
                                 if heads[0] is not None)
    newmap.update(repo, (ctx.rev() for ctx in missingctx))
    for branch, newheads in newmap.iteritems():
        headssum[branch][1][:] = newheads
    return headssum

def _oldheadssummary(repo, remoteheads, outgoing, inc=False):
    """Compute branchmapsummary for repo without branchmap support"""

    # 1-4b. old servers: Check for new topological heads.
    # Construct {old,new}map with branch = None (topological branch).
    # (code based on update)
    knownnode = repo.changelog.hasnode # no nodemap until it is filtered
    oldheads = set(h for h in remoteheads if knownnode(h))
    # all nodes in outgoing.missing are children of either:
    # - an element of oldheads
    # - another element of outgoing.missing
    # - nullrev
    # This explains why the new head are very simple to compute.
    r = repo.set('heads(%ln + %ln)', oldheads, outgoing.missing)
    newheads = list(c.node() for c in r)
    # set some unsynced head to issue the "unsynced changes" warning
    if inc:
        unsynced = set([None])
    else:
        unsynced = set()
    return {None: (oldheads, newheads, unsynced)}

def _nowarnheads(pushop):
    # Compute newly pushed bookmarks. We don't warn about bookmarked heads.
    repo = pushop.repo.unfiltered()
    remote = pushop.remote
    localbookmarks = repo._bookmarks
    remotebookmarks = remote.listkeys('bookmarks')
    bookmarkedheads = set()

    # internal config: bookmarks.pushing
    newbookmarks = [localbookmarks.expandname(b)
                    for b in pushop.ui.configlist('bookmarks', 'pushing')]

    for bm in localbookmarks:
        rnode = remotebookmarks.get(bm)
        if rnode and rnode in repo:
            lctx, rctx = repo[bm], repo[rnode]
            if bookmarks.validdest(repo, rctx, lctx):
                bookmarkedheads.add(lctx.node())
        else:
            if bm in newbookmarks and bm not in remotebookmarks:
                bookmarkedheads.add(repo[bm].node())

    return bookmarkedheads

def checkheads(pushop):
    """Check that a push won't add any outgoing head

    raise Abort error and display ui message as needed.
    """

    repo = pushop.repo.unfiltered()
    remote = pushop.remote
    outgoing = pushop.outgoing
    remoteheads = pushop.remoteheads
    newbranch = pushop.newbranch
    inc = bool(pushop.incoming)

    # 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
    if remoteheads == [nullid]:
        # remote is empty, nothing to check.
        return

    if remote.capable('branchmap'):
        headssum = _headssummary(repo, remote, outgoing)
    else:
        headssum = _oldheadssummary(repo, remoteheads, outgoing, inc)
    newbranches = [branch for branch, heads in headssum.iteritems()
                   if heads[0] is None]
    # 1. Check for new branches on the remote.
    if newbranches and not newbranch:  # new branch requires --new-branch
        branchnames = ', '.join(sorted(newbranches))
        raise error.Abort(_("push creates new remote branches: %s!")
                           % branchnames,
                         hint=_("use 'hg push --new-branch' to create"
                                " new remote branches"))

    # 2. Find heads that we need not warn about
    nowarnheads = _nowarnheads(pushop)

    # 3. Check for new heads.
    # If there are more heads after the push than before, a suitable
    # error message, depending on unsynced status, is displayed.
    errormsg = None
    # If there is no obsstore, allfuturecommon won't be used, so no
    # need to compute it.
    if repo.obsstore:
        allmissing = set(outgoing.missing)
        cctx = repo.set('%ld', outgoing.common)
        allfuturecommon = set(c.node() for c in cctx)
        allfuturecommon.update(allmissing)
    for branch, heads in sorted(headssum.iteritems()):
        remoteheads, newheads, unsyncedheads = heads
        candidate_newhs = set(newheads)
        # add unsynced data
        if remoteheads is None:
            oldhs = set()
        else:
            oldhs = set(remoteheads)
        oldhs.update(unsyncedheads)
        candidate_newhs.update(unsyncedheads)
        dhs = None # delta heads, the new heads on branch
        if not repo.obsstore:
            discardedheads = set()
            newhs = candidate_newhs
        else:
            newhs, discardedheads = _postprocessobsolete(pushop,
                                                         allfuturecommon,
                                                         candidate_newhs)
        unsynced = sorted(h for h in unsyncedheads if h not in discardedheads)
        if unsynced:
            if None in unsynced:
                # old remote, no heads data
                heads = None
            elif len(unsynced) <= 4 or repo.ui.verbose:
                heads = ' '.join(short(h) for h in unsynced)
            else:
                heads = (' '.join(short(h) for h in unsynced[:4]) +
                         ' ' + _("and %s others") % (len(unsynced) - 4))
            if heads is None:
                repo.ui.status(_("remote has heads that are "
                                 "not known locally\n"))
            elif branch is None:
                repo.ui.status(_("remote has heads that are "
                                 "not known locally: %s\n") % heads)
            else:
                repo.ui.status(_("remote has heads on branch '%s' that are "
                                 "not known locally: %s\n") % (branch, heads))
        if remoteheads is None:
            if len(newhs) > 1:
                dhs = list(newhs)
                if errormsg is None:
                    errormsg = (_("push creates new branch '%s' "
                                  "with multiple heads") % (branch))
                    hint = _("merge or"
                             " see 'hg help push' for details about"
                             " pushing new heads")
        elif len(newhs) > len(oldhs):
            # remove bookmarked or existing remote heads from the new heads list
            dhs = sorted(newhs - nowarnheads - oldhs)
        if dhs:
            if errormsg is None:
                if branch not in ('default', None):
                    errormsg = _("push creates new remote head %s "
                                 "on branch '%s'!") % (short(dhs[0]), branch)
                elif repo[dhs[0]].bookmarks():
                    errormsg = _("push creates new remote head %s "
                                 "with bookmark '%s'!") % (
                                 short(dhs[0]), repo[dhs[0]].bookmarks()[0])
                else:
                    errormsg = _("push creates new remote head %s!"
                                 ) % short(dhs[0])
                if unsyncedheads:
                    hint = _("pull and merge or"
                             " see 'hg help push' for details about"
                             " pushing new heads")
                else:
                    hint = _("merge or"
                             " see 'hg help push' for details about"
                             " pushing new heads")
            if branch is None:
                repo.ui.note(_("new remote heads:\n"))
            else:
                repo.ui.note(_("new remote heads on branch '%s':\n") % branch)
            for h in dhs:
                repo.ui.note((" %s\n") % short(h))
    if errormsg:
        raise error.Abort(errormsg, hint=hint)

def _postprocessobsolete(pushop, futurecommon, candidate_newhs):
    """post process the list of new heads with obsolescence information

    Exists as a subfunction to contain the complexity and allow extensions to
    experiment with smarter logic.
    Returns (newheads, discarded_heads) tuple
    """
    # remove future heads which are actually obsoleted by another
    # pushed element:
    #
    # XXX as above, There are several cases this code does not handle
    # XXX properly
    #
    # (1) if <nh> is public, it won't be affected by obsolete marker
    #     and a new is created
    #
    # (2) if the new heads have ancestors which are not obsolete and
    #     not ancestors of any other heads we will have a new head too.
    #
    # These two cases will be easy to handle for known changeset but
    # much more tricky for unsynced changes.
    #
    # In addition, this code is confused by prune as it only looks for
    # successors of the heads (none if pruned) leading to issue4354
    repo = pushop.repo
    newhs = set()
    discarded = set()
    for nh in candidate_newhs:
        if nh in repo and repo[nh].phase() <= phases.public:
            newhs.add(nh)
        else:
            for suc in obsolete.allsuccessors(repo.obsstore, [nh]):
                if suc != nh and suc in futurecommon:
                    discarded.add(nh)
                    break
            else:
                newhs.add(nh)
    return newhs, discarded