view mercurial/ancestor.py @ 50336:cf4d2f31660d stable

chg: populate CHGHG if not set

Normally, chg determines which `hg` executable to use by first consulting the
`$CHGHG` and `$HG` environment variables, and if neither are present defaults
to the `hg` found in the user's `$PATH`. If built with the `HGPATHREL` compiler
flag, chg will instead assume that there exists an `hg` executable in the same
directory as the `chg` binary and attempt to use that.

This can cause problems in situations where there are multiple actively-used
Mercurial installations on the same system. When a `chg` client connects to a
running command server, the server process performs some basic validation to
determine whether a new command server needs to be spawned. These checks include
things like checking certain "sensitive" environment variables and config
sections, as well as checking whether the mtime of the extensions, hg's
`__version__.py` module, and the Python interpreter have changed.

Crucially, the command server doesn't explicitly check whether the executable it
is running from matches the executable that the `chg` client would have
otherwise invoked had there been no existing command server process. Without
`HGPATHREL`, this still gets implicitly checked during the validation step,
because the only way to specify an alternate hg executable (apart from `$PATH`)
is via the `$CHGHG` and `$HG` environment variables, both of which are checked.

With `HGPATHREL`, however, the command server has no way of knowing which hg
executable the client would have run. This means that a client located at
`/version_B/bin/chg` will happily connect to a command server running
`/version_A/bin/hg` instead of `/version_B/bin/hg` as expected. A simple
solution is to have the client set `$CHGHG` itself, which then allows the
command server's environment validation to work as intended.

I have tested this manually using two locally built hg installations and it
seems to work with no ill effects. That said, I'm not sure how to write an
automated test for this since the `chg` available to the tests isn't even built
with the `HGPATHREL` compiler flag to begin with.

# ancestor.py - generic DAG ancestor algorithm for mercurial
#
# Copyright 2006 Olivia 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.


import heapq

from .node import nullrev
from . import (
    dagop,
    policy,
)

parsers = policy.importmod('parsers')


def commonancestorsheads(pfunc, *nodes):
    """Returns a set with the heads of all common ancestors of all nodes,
    heads(::nodes[0] and ::nodes[1] and ...) .

    pfunc must return a list of parent vertices for a given vertex.
    """
    if not isinstance(nodes, set):
        nodes = set(nodes)
    if nullrev in nodes:
        return set()
    if len(nodes) <= 1:
        return nodes

    allseen = (1 << len(nodes)) - 1
    seen = [0] * (max(nodes) + 1)
    for i, n in enumerate(nodes):
        seen[n] = 1 << i
    poison = 1 << (i + 1)

    gca = set()
    interesting = len(nodes)
    nv = len(seen) - 1
    while nv >= 0 and interesting:
        v = nv
        nv -= 1
        if not seen[v]:
            continue
        sv = seen[v]
        if sv < poison:
            interesting -= 1
            if sv == allseen:
                gca.add(v)
                sv |= poison
                if v in nodes:
                    # history is linear
                    return {v}
        if sv < poison:
            for p in pfunc(v):
                sp = seen[p]
                if p == nullrev:
                    continue
                if sp == 0:
                    seen[p] = sv
                    interesting += 1
                elif sp != sv:
                    seen[p] |= sv
        else:
            for p in pfunc(v):
                if p == nullrev:
                    continue
                sp = seen[p]
                if sp and sp < poison:
                    interesting -= 1
                seen[p] = sv
    return gca


def ancestors(pfunc, *orignodes):
    """
    Returns the common ancestors of a and b that are furthest from a
    root (as measured by longest path).

    pfunc must return a list of parent vertices for a given vertex.
    """

    def deepest(nodes):
        interesting = {}
        count = max(nodes) + 1
        depth = [0] * count
        seen = [0] * count
        mapping = []
        for (i, n) in enumerate(sorted(nodes)):
            depth[n] = 1
            b = 1 << i
            seen[n] = b
            interesting[b] = 1
            mapping.append((b, n))
        nv = count - 1
        while nv >= 0 and len(interesting) > 1:
            v = nv
            nv -= 1
            dv = depth[v]
            if dv == 0:
                continue
            sv = seen[v]
            for p in pfunc(v):
                if p == nullrev:
                    continue
                dp = depth[p]
                sp = seen[p]
                if dp <= dv:
                    depth[p] = dv + 1
                    if sp != sv:
                        interesting[sv] += 1
                        seen[p] = sv
                        if sp:
                            interesting[sp] -= 1
                            if interesting[sp] == 0:
                                del interesting[sp]
                elif dv == dp - 1:
                    nsp = sp | sv
                    if nsp == sp:
                        continue
                    seen[p] = nsp
                    interesting.setdefault(nsp, 0)
                    interesting[nsp] += 1
                    interesting[sp] -= 1
                    if interesting[sp] == 0:
                        del interesting[sp]
            interesting[sv] -= 1
            if interesting[sv] == 0:
                del interesting[sv]

        if len(interesting) != 1:
            return []

        k = 0
        for i in interesting:
            k |= i
        return {n for (i, n) in mapping if k & i}

    gca = commonancestorsheads(pfunc, *orignodes)

    if len(gca) <= 1:
        return gca
    return deepest(gca)


class incrementalmissingancestors:
    """persistent state used to calculate missing ancestors incrementally

    Although similar in spirit to lazyancestors below, this is a separate class
    because trying to support contains and missingancestors operations with the
    same internal data structures adds needless complexity."""

    def __init__(self, pfunc, bases):
        self.bases = set(bases)
        if not self.bases:
            self.bases.add(nullrev)
        self.pfunc = pfunc

    def hasbases(self):
        '''whether the common set has any non-trivial bases'''
        return self.bases and self.bases != {nullrev}

    def addbases(self, newbases):
        '''grow the ancestor set by adding new bases'''
        self.bases.update(newbases)

    def basesheads(self):
        return dagop.headrevs(self.bases, self.pfunc)

    def removeancestorsfrom(self, revs):
        '''remove all ancestors of bases from the set revs (in place)'''
        bases = self.bases
        pfunc = self.pfunc
        revs.difference_update(bases)
        # nullrev is always an ancestor
        revs.discard(nullrev)
        if not revs:
            return
        # anything in revs > start is definitely not an ancestor of bases
        # revs <= start needs to be investigated
        start = max(bases)
        keepcount = sum(1 for r in revs if r > start)
        if len(revs) == keepcount:
            # no revs to consider
            return

        for curr in range(start, min(revs) - 1, -1):
            if curr not in bases:
                continue
            revs.discard(curr)
            bases.update(pfunc(curr))
            if len(revs) == keepcount:
                # no more potential revs to discard
                break

    def missingancestors(self, revs):
        """return all the ancestors of revs that are not ancestors of self.bases

        This may include elements from revs.

        Equivalent to the revset (::revs - ::self.bases). Revs are returned in
        revision number order, which is a topological order."""
        revsvisit = set(revs)
        basesvisit = self.bases
        pfunc = self.pfunc
        bothvisit = revsvisit.intersection(basesvisit)
        revsvisit.difference_update(bothvisit)
        if not revsvisit:
            return []

        start = max(max(revsvisit), max(basesvisit))
        # At this point, we hold the invariants that:
        # - revsvisit is the set of nodes we know are an ancestor of at least
        #   one of the nodes in revs
        # - basesvisit is the same for bases
        # - bothvisit is the set of nodes we know are ancestors of at least one
        #   of the nodes in revs and one of the nodes in bases. bothvisit and
        #   revsvisit are mutually exclusive, but bothvisit is a subset of
        #   basesvisit.
        # Now we walk down in reverse topo order, adding parents of nodes
        # already visited to the sets while maintaining the invariants. When a
        # node is found in both revsvisit and basesvisit, it is removed from
        # revsvisit and added to bothvisit. When revsvisit becomes empty, there
        # are no more ancestors of revs that aren't also ancestors of bases, so
        # exit.

        missing = []
        for curr in range(start, nullrev, -1):
            if not revsvisit:
                break

            if curr in bothvisit:
                bothvisit.remove(curr)
                # curr's parents might have made it into revsvisit through
                # another path
                for p in pfunc(curr):
                    revsvisit.discard(p)
                    basesvisit.add(p)
                    bothvisit.add(p)
                continue

            if curr in revsvisit:
                missing.append(curr)
                revsvisit.remove(curr)
                thisvisit = revsvisit
                othervisit = basesvisit
            elif curr in basesvisit:
                thisvisit = basesvisit
                othervisit = revsvisit
            else:
                # not an ancestor of revs or bases: ignore
                continue

            for p in pfunc(curr):
                if p == nullrev:
                    pass
                elif p in othervisit or p in bothvisit:
                    # p is implicitly in thisvisit. This means p is or should be
                    # in bothvisit
                    revsvisit.discard(p)
                    basesvisit.add(p)
                    bothvisit.add(p)
                else:
                    # visit later
                    thisvisit.add(p)

        missing.reverse()
        return missing


# Extracted from lazyancestors.__iter__ to avoid a reference cycle
def _lazyancestorsiter(parentrevs, initrevs, stoprev, inclusive):
    seen = {nullrev}
    heappush = heapq.heappush
    heappop = heapq.heappop
    heapreplace = heapq.heapreplace
    see = seen.add

    if inclusive:
        visit = [-r for r in initrevs]
        seen.update(initrevs)
        heapq.heapify(visit)
    else:
        visit = []
        heapq.heapify(visit)
        for r in initrevs:
            p1, p2 = parentrevs(r)
            if p1 not in seen:
                heappush(visit, -p1)
                see(p1)
            if p2 not in seen:
                heappush(visit, -p2)
                see(p2)

    while visit:
        current = -visit[0]
        if current < stoprev:
            break
        yield current
        # optimize out heapq operation if p1 is known to be the next highest
        # revision, which is quite common in linear history.
        p1, p2 = parentrevs(current)
        if p1 not in seen:
            if current - p1 == 1:
                visit[0] = -p1
            else:
                heapreplace(visit, -p1)
            see(p1)
        else:
            heappop(visit)
        if p2 not in seen:
            heappush(visit, -p2)
            see(p2)


class lazyancestors:
    def __init__(self, pfunc, revs, stoprev=0, inclusive=False):
        """Create a new object generating ancestors for the given revs. Does
        not generate revs lower than stoprev.

        This is computed lazily starting from revs. The object supports
        iteration and membership.

        cl should be a changelog and revs should be an iterable. inclusive is
        a boolean that indicates whether revs should be included. Revs lower
        than stoprev will not be generated.

        Result does not include the null revision."""
        self._parentrevs = pfunc
        self._initrevs = [r for r in revs if r >= stoprev]
        self._stoprev = stoprev
        self._inclusive = inclusive

        self._containsseen = set()
        self._containsiter = _lazyancestorsiter(
            self._parentrevs, self._initrevs, self._stoprev, self._inclusive
        )

    def __nonzero__(self):
        """False if the set is empty, True otherwise."""
        try:
            next(iter(self))
            return True
        except StopIteration:
            return False

    __bool__ = __nonzero__

    def __iter__(self):
        """Generate the ancestors of _initrevs in reverse topological order.

        If inclusive is False, yield a sequence of revision numbers starting
        with the parents of each revision in revs, i.e., each revision is
        *not* considered an ancestor of itself. Results are emitted in reverse
        revision number order. That order is also topological: a child is
        always emitted before its parent.

        If inclusive is True, the source revisions are also yielded. The
        reverse revision number order is still enforced."""
        return _lazyancestorsiter(
            self._parentrevs, self._initrevs, self._stoprev, self._inclusive
        )

    def __contains__(self, target):
        """Test whether target is an ancestor of self._initrevs."""
        seen = self._containsseen
        if target in seen:
            return True
        iter = self._containsiter
        if iter is None:
            # Iterator exhausted
            return False
        # Only integer target is valid, but some callers expect 'None in self'
        # to be False. So we explicitly allow it.
        if target is None:
            return False

        see = seen.add
        try:
            while True:
                rev = next(iter)
                see(rev)
                if rev == target:
                    return True
                if rev < target:
                    return False
        except StopIteration:
            # Set to None to indicate fast-path can be used next time, and to
            # free up memory.
            self._containsiter = None
            return False