mercurial/revset.py

revlog: improve delta generation heuristics for generaldelta

Without this change, pulls (and clones) into a generaldelta repository could
generate very inefficient revlogs, the size of which could be at least twice
the original size.

This was caused by the generated delta chains covering too large distances,
causing new chains to be built far too often. This change addresses the
problem by forcing a delta against second parent or against the previous
revision, when the first parent delta is in danger of creating a long chain.

# revset.py - revision set queries for mercurial
#
# 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.

import re
import parser, util, error, discovery, help, hbisect
import bookmarks as bookmarksmod
import match as matchmod
from i18n import _

elements = {
    "(": (20, ("group", 1, ")"), ("func", 1, ")")),
    "~": (18, None, ("ancestor", 18)),
    "^": (18, None, ("parent", 18), ("parentpost", 18)),
    "-": (5, ("negate", 19), ("minus", 5)),
    "::": (17, ("dagrangepre", 17), ("dagrange", 17),
           ("dagrangepost", 17)),
    "..": (17, ("dagrangepre", 17), ("dagrange", 17),
           ("dagrangepost", 17)),
    ":": (15, ("rangepre", 15), ("range", 15), ("rangepost", 15)),
    "not": (10, ("not", 10)),
    "!": (10, ("not", 10)),
    "and": (5, None, ("and", 5)),
    "&": (5, None, ("and", 5)),
    "or": (4, None, ("or", 4)),
    "|": (4, None, ("or", 4)),
    "+": (4, None, ("or", 4)),
    ",": (2, None, ("list", 2)),
    ")": (0, None, None),
    "symbol": (0, ("symbol",), None),
    "string": (0, ("string",), None),
    "end": (0, None, None),
}

keywords = set(['and', 'or', 'not'])

def tokenize(program):
    pos, l = 0, len(program)
    while pos < l:
        c = program[pos]
        if c.isspace(): # skip inter-token whitespace
            pass
        elif c == ':' and program[pos:pos + 2] == '::': # look ahead carefully
            yield ('::', None, pos)
            pos += 1 # skip ahead
        elif c == '.' and program[pos:pos + 2] == '..': # look ahead carefully
            yield ('..', None, pos)
            pos += 1 # skip ahead
        elif c in "():,-|&+!~^": # handle simple operators
            yield (c, None, pos)
        elif (c in '"\'' or c == 'r' and
              program[pos:pos + 2] in ("r'", 'r"')): # handle quoted strings
            if c == 'r':
                pos += 1
                c = program[pos]
                decode = lambda x: x
            else:
                decode = lambda x: x.decode('string-escape')
            pos += 1
            s = pos
            while pos < l: # find closing quote
                d = program[pos]
                if d == '\\': # skip over escaped characters
                    pos += 2
                    continue
                if d == c:
                    yield ('string', decode(program[s:pos]), s)
                    break
                pos += 1
            else:
                raise error.ParseError(_("unterminated string"), s)
        elif c.isalnum() or c in '._' or ord(c) > 127: # gather up a symbol/keyword
            s = pos
            pos += 1
            while pos < l: # find end of symbol
                d = program[pos]
                if not (d.isalnum() or d in "._" or ord(d) > 127):
                    break
                if d == '.' and program[pos - 1] == '.': # special case for ..
                    pos -= 1
                    break
                pos += 1
            sym = program[s:pos]
            if sym in keywords: # operator keywords
                yield (sym, None, s)
            else:
                yield ('symbol', sym, s)
            pos -= 1
        else:
            raise error.ParseError(_("syntax error"), pos)
        pos += 1
    yield ('end', None, pos)

# helpers

def getstring(x, err):
    if x and (x[0] == 'string' or x[0] == 'symbol'):
        return x[1]
    raise error.ParseError(err)

def getlist(x):
    if not x:
        return []
    if x[0] == 'list':
        return getlist(x[1]) + [x[2]]
    return [x]

def getargs(x, min, max, err):
    l = getlist(x)
    if len(l) < min or len(l) > max:
        raise error.ParseError(err)
    return l

def getset(repo, subset, x):
    if not x:
        raise error.ParseError(_("missing argument"))
    return methods[x[0]](repo, subset, *x[1:])

# operator methods

def stringset(repo, subset, x):
    x = repo[x].rev()
    if x == -1 and len(subset) == len(repo):
        return [-1]
    if len(subset) == len(repo) or x in subset:
        return [x]
    return []

def symbolset(repo, subset, x):
    if x in symbols:
        raise error.ParseError(_("can't use %s here") % x)
    return stringset(repo, subset, x)

def rangeset(repo, subset, x, y):
    m = getset(repo, subset, x)
    if not m:
        m = getset(repo, range(len(repo)), x)

    n = getset(repo, subset, y)
    if not n:
        n = getset(repo, range(len(repo)), y)

    if not m or not n:
        return []
    m, n = m[0], n[-1]

    if m < n:
        r = range(m, n + 1)
    else:
        r = range(m, n - 1, -1)
    s = set(subset)
    return [x for x in r if x in s]

def andset(repo, subset, x, y):
    return getset(repo, getset(repo, subset, x), y)

def orset(repo, subset, x, y):
    xl = getset(repo, subset, x)
    s = set(xl)
    yl = getset(repo, [r for r in subset if r not in s], y)
    return xl + yl

def notset(repo, subset, x):
    s = set(getset(repo, subset, x))
    return [r for r in subset if r not in s]

def listset(repo, subset, a, b):
    raise error.ParseError(_("can't use a list in this context"))

def func(repo, subset, a, b):
    if a[0] == 'symbol' and a[1] in symbols:
        return symbols[a[1]](repo, subset, b)
    raise error.ParseError(_("not a function: %s") % a[1])

# functions

def adds(repo, subset, x):
    """``adds(pattern)``
    Changesets that add a file matching pattern.
    """
    # i18n: "adds" is a keyword
    pat = getstring(x, _("adds requires a pattern"))
    return checkstatus(repo, subset, pat, 1)

def ancestor(repo, subset, x):
    """``ancestor(single, single)``
    Greatest common ancestor of the two changesets.
    """
    # i18n: "ancestor" is a keyword
    l = getargs(x, 2, 2, _("ancestor requires two arguments"))
    r = range(len(repo))
    a = getset(repo, r, l[0])
    b = getset(repo, r, l[1])
    if len(a) != 1 or len(b) != 1:
        # i18n: "ancestor" is a keyword
        raise error.ParseError(_("ancestor arguments must be single revisions"))
    an = [repo[a[0]].ancestor(repo[b[0]]).rev()]

    return [r for r in an if r in subset]

def ancestors(repo, subset, x):
    """``ancestors(set)``
    Changesets that are ancestors of a changeset in set.
    """
    args = getset(repo, range(len(repo)), x)
    if not args:
        return []
    s = set(repo.changelog.ancestors(*args)) | set(args)
    return [r for r in subset if r in s]

def ancestorspec(repo, subset, x, n):
    """``set~n``
    Changesets that are the Nth ancestor (first parents only) of a changeset in set.
    """
    try:
        n = int(n[1])
    except ValueError:
        raise error.ParseError(_("~ expects a number"))
    ps = set()
    cl = repo.changelog
    for r in getset(repo, subset, x):
        for i in range(n):
            r = cl.parentrevs(r)[0]
        ps.add(r)
    return [r for r in subset if r in ps]

def author(repo, subset, x):
    """``author(string)``
    Alias for ``user(string)``.
    """
    # i18n: "author" is a keyword
    n = getstring(x, _("author requires a string")).lower()
    return [r for r in subset if n in repo[r].user().lower()]

def bisected(repo, subset, x):
    """``bisected(string)``
    Changesets marked in the specified bisect state (good, bad, skip).
    """
    state = getstring(x, _("bisect requires a string")).lower()
    if state not in ('good', 'bad', 'skip', 'unknown'):
        raise error.ParseError(_('invalid bisect state'))
    marked = set(repo.changelog.rev(n) for n in hbisect.load_state(repo)[state])
    return [r for r in subset if r in marked]

def bookmark(repo, subset, x):
    """``bookmark([name])``
    The named bookmark or all bookmarks.
    """
    # i18n: "bookmark" is a keyword
    args = getargs(x, 0, 1, _('bookmark takes one or no arguments'))
    if args:
        bm = getstring(args[0],
                       # i18n: "bookmark" is a keyword
                       _('the argument to bookmark must be a string'))
        bmrev = bookmarksmod.listbookmarks(repo).get(bm, None)
        if not bmrev:
            raise util.Abort(_("bookmark '%s' does not exist") % bm)
        bmrev = repo[bmrev].rev()
        return [r for r in subset if r == bmrev]
    bms = set([repo[r].rev()
               for r in bookmarksmod.listbookmarks(repo).values()])
    return [r for r in subset if r in bms]

def branch(repo, subset, x):
    """``branch(string or set)``
    All changesets belonging to the given branch or the branches of the given
    changesets.
    """
    try:
        b = getstring(x, '')
        if b in repo.branchmap():
            return [r for r in subset if repo[r].branch() == b]
    except error.ParseError:
        # not a string, but another revspec, e.g. tip()
        pass

    s = getset(repo, range(len(repo)), x)
    b = set()
    for r in s:
        b.add(repo[r].branch())
    s = set(s)
    return [r for r in subset if r in s or repo[r].branch() in b]

def checkstatus(repo, subset, pat, field):
    m = matchmod.match(repo.root, repo.getcwd(), [pat])
    s = []
    fast = (m.files() == [pat])
    for r in subset:
        c = repo[r]
        if fast:
            if pat not in c.files():
                continue
        else:
            for f in c.files():
                if m(f):
                    break
            else:
                continue
        files = repo.status(c.p1().node(), c.node())[field]
        if fast:
            if pat in files:
                s.append(r)
        else:
            for f in files:
                if m(f):
                    s.append(r)
                    break
    return s

def children(repo, subset, x):
    """``children(set)``
    Child changesets of changesets in set.
    """
    cs = set()
    cl = repo.changelog
    s = set(getset(repo, range(len(repo)), x))
    for r in xrange(0, len(repo)):
        for p in cl.parentrevs(r):
            if p in s:
                cs.add(r)
    return [r for r in subset if r in cs]

def closed(repo, subset, x):
    """``closed()``
    Changeset is closed.
    """
    # i18n: "closed" is a keyword
    getargs(x, 0, 0, _("closed takes no arguments"))
    return [r for r in subset if repo[r].extra().get('close')]

def contains(repo, subset, x):
    """``contains(pattern)``
    Revision contains pattern.
    """
    # i18n: "contains" is a keyword
    pat = getstring(x, _("contains requires a pattern"))
    m = matchmod.match(repo.root, repo.getcwd(), [pat])
    s = []
    if m.files() == [pat]:
        for r in subset:
            if pat in repo[r]:
                s.append(r)
    else:
        for r in subset:
            for f in repo[r].manifest():
                if m(f):
                    s.append(r)
                    break
    return s

def date(repo, subset, x):
    """``date(interval)``
    Changesets within the interval, see :hg:`help dates`.
    """
    # i18n: "date" is a keyword
    ds = getstring(x, _("date requires a string"))
    dm = util.matchdate(ds)
    return [r for r in subset if dm(repo[r].date()[0])]

def descendants(repo, subset, x):
    """``descendants(set)``
    Changesets which are descendants of changesets in set.
    """
    args = getset(repo, range(len(repo)), x)
    if not args:
        return []
    s = set(repo.changelog.descendants(*args)) | set(args)
    return [r for r in subset if r in s]

def follow(repo, subset, x):
    """``follow()``
    An alias for ``::.`` (ancestors of the working copy's first parent).
    """
    # i18n: "follow" is a keyword
    getargs(x, 0, 0, _("follow takes no arguments"))
    p = repo['.'].rev()
    s = set(repo.changelog.ancestors(p)) | set([p])
    return [r for r in subset if r in s]

def getall(repo, subset, x):
    """``all()``
    All changesets, the same as ``0:tip``.
    """
    # i18n: "all" is a keyword
    getargs(x, 0, 0, _("all takes no arguments"))
    return subset

def grep(repo, subset, x):
    """``grep(regex)``
    Like ``keyword(string)`` but accepts a regex. Use ``grep(r'...')``
    to ensure special escape characters are handled correctly.
    """
    try:
        # i18n: "grep" is a keyword
        gr = re.compile(getstring(x, _("grep requires a string")))
    except re.error, e:
        raise error.ParseError(_('invalid match pattern: %s') % e)
    l = []
    for r in subset:
        c = repo[r]
        for e in c.files() + [c.user(), c.description()]:
            if gr.search(e):
                l.append(r)
                break
    return l

def hasfile(repo, subset, x):
    """``file(pattern)``
    Changesets affecting files matched by pattern.
    """
    # i18n: "file" is a keyword
    pat = getstring(x, _("file requires a pattern"))
    m = matchmod.match(repo.root, repo.getcwd(), [pat])
    s = []
    for r in subset:
        for f in repo[r].files():
            if m(f):
                s.append(r)
                break
    return s

def head(repo, subset, x):
    """``head()``
    Changeset is a named branch head.
    """
    # i18n: "head" is a keyword
    getargs(x, 0, 0, _("head takes no arguments"))
    hs = set()
    for b, ls in repo.branchmap().iteritems():
        hs.update(repo[h].rev() for h in ls)
    return [r for r in subset if r in hs]

def heads(repo, subset, x):
    """``heads(set)``
    Members of set with no children in set.
    """
    s = getset(repo, subset, x)
    ps = set(parents(repo, subset, x))
    return [r for r in s if r not in ps]

def keyword(repo, subset, x):
    """``keyword(string)``
    Search commit message, user name, and names of changed files for
    string.
    """
    # i18n: "keyword" is a keyword
    kw = getstring(x, _("keyword requires a string")).lower()
    l = []
    for r in subset:
        c = repo[r]
        t = " ".join(c.files() + [c.user(), c.description()])
        if kw in t.lower():
            l.append(r)
    return l

def limit(repo, subset, x):
    """``limit(set, n)``
    First n members of set.
    """
    # i18n: "limit" is a keyword
    l = getargs(x, 2, 2, _("limit requires two arguments"))
    try:
        # i18n: "limit" is a keyword
        lim = int(getstring(l[1], _("limit requires a number")))
    except ValueError:
        # i18n: "limit" is a keyword
        raise error.ParseError(_("limit expects a number"))
    ss = set(subset)
    os = getset(repo, range(len(repo)), l[0])[:lim]
    return [r for r in os if r in ss]

def last(repo, subset, x):
    """``last(set, n)``
    Last n members of set.
    """
    # i18n: "last" is a keyword
    l = getargs(x, 2, 2, _("last requires two arguments"))
    try:
        # i18n: "last" is a keyword
        lim = int(getstring(l[1], _("last requires a number")))
    except ValueError:
        # i18n: "last" is a keyword
        raise error.ParseError(_("last expects a number"))
    ss = set(subset)
    os = getset(repo, range(len(repo)), l[0])[-lim:]
    return [r for r in os if r in ss]

def maxrev(repo, subset, x):
    """``max(set)``
    Changeset with highest revision number in set.
    """
    os = getset(repo, range(len(repo)), x)
    if os:
        m = max(os)
        if m in subset:
            return [m]
    return []

def merge(repo, subset, x):
    """``merge()``
    Changeset is a merge changeset.
    """
    # i18n: "merge" is a keyword
    getargs(x, 0, 0, _("merge takes no arguments"))
    cl = repo.changelog
    return [r for r in subset if cl.parentrevs(r)[1] != -1]

def minrev(repo, subset, x):
    """``min(set)``
    Changeset with lowest revision number in set.
    """
    os = getset(repo, range(len(repo)), x)
    if os:
        m = min(os)
        if m in subset:
            return [m]
    return []

def modifies(repo, subset, x):
    """``modifies(pattern)``
    Changesets modifying files matched by pattern.
    """
    # i18n: "modifies" is a keyword
    pat = getstring(x, _("modifies requires a pattern"))
    return checkstatus(repo, subset, pat, 0)

def node(repo, subset, x):
    """``id(string)``
    Revision non-ambiguously specified by the given hex string prefix.
    """
    # i18n: "id" is a keyword
    l = getargs(x, 1, 1, _("id requires one argument"))
    # i18n: "id" is a keyword
    n = getstring(l[0], _("id requires a string"))
    if len(n) == 40:
        rn = repo[n].rev()
    else:
        rn = repo.changelog.rev(repo.changelog._partialmatch(n))
    return [r for r in subset if r == rn]

def outgoing(repo, subset, x):
    """``outgoing([path])``
    Changesets not found in the specified destination repository, or the
    default push location.
    """
    import hg # avoid start-up nasties
    # i18n: "outgoing" is a keyword
    l = getargs(x, 0, 1, _("outgoing requires a repository path"))
    # i18n: "outgoing" is a keyword
    dest = l and getstring(l[0], _("outgoing requires a repository path")) or ''
    dest = repo.ui.expandpath(dest or 'default-push', dest or 'default')
    dest, branches = hg.parseurl(dest)
    revs, checkout = hg.addbranchrevs(repo, repo, branches, [])
    if revs:
        revs = [repo.lookup(rev) for rev in revs]
    other = hg.repository(hg.remoteui(repo, {}), dest)
    repo.ui.pushbuffer()
    common, outheads = discovery.findcommonoutgoing(repo, other, onlyheads=revs)
    repo.ui.popbuffer()
    cl = repo.changelog
    o = set([cl.rev(r) for r in repo.changelog.findmissing(common, outheads)])
    return [r for r in subset if r in o]

def p1(repo, subset, x):
    """``p1([set])``
    First parent of changesets in set, or the working directory.
    """
    if x is None:
        p = repo[x].p1().rev()
        return [r for r in subset if r == p]

    ps = set()
    cl = repo.changelog
    for r in getset(repo, range(len(repo)), x):
        ps.add(cl.parentrevs(r)[0])
    return [r for r in subset if r in ps]

def p2(repo, subset, x):
    """``p2([set])``
    Second parent of changesets in set, or the working directory.
    """
    if x is None:
        ps = repo[x].parents()
        try:
            p = ps[1].rev()
            return [r for r in subset if r == p]
        except IndexError:
            return []

    ps = set()
    cl = repo.changelog
    for r in getset(repo, range(len(repo)), x):
        ps.add(cl.parentrevs(r)[1])
    return [r for r in subset if r in ps]

def parents(repo, subset, x):
    """``parents([set])``
    The set of all parents for all changesets in set, or the working directory.
    """
    if x is None:
        ps = tuple(p.rev() for p in repo[x].parents())
        return [r for r in subset if r in ps]

    ps = set()
    cl = repo.changelog
    for r in getset(repo, range(len(repo)), x):
        ps.update(cl.parentrevs(r))
    return [r for r in subset if r in ps]

def parentspec(repo, subset, x, n):
    """``set^0``
    The set.
    ``set^1`` (or ``set^``), ``set^2``
    First or second parent, respectively, of all changesets in set.
    """
    try:
        n = int(n[1])
        if n not in (0, 1, 2):
            raise ValueError
    except ValueError:
        raise error.ParseError(_("^ expects a number 0, 1, or 2"))
    ps = set()
    cl = repo.changelog
    for r in getset(repo, subset, x):
        if n == 0:
            ps.add(r)
        elif n == 1:
            ps.add(cl.parentrevs(r)[0])
        elif n == 2:
            parents = cl.parentrevs(r)
            if len(parents) > 1:
                ps.add(parents[1])
    return [r for r in subset if r in ps]

def present(repo, subset, x):
    """``present(set)``
    An empty set, if any revision in set isn't found; otherwise,
    all revisions in set.
    """
    try:
        return getset(repo, subset, x)
    except error.RepoLookupError:
        return []

def removes(repo, subset, x):
    """``removes(pattern)``
    Changesets which remove files matching pattern.
    """
    # i18n: "removes" is a keyword
    pat = getstring(x, _("removes requires a pattern"))
    return checkstatus(repo, subset, pat, 2)

def rev(repo, subset, x):
    """``rev(number)``
    Revision with the given numeric identifier.
    """
    # i18n: "rev" is a keyword
    l = getargs(x, 1, 1, _("rev requires one argument"))
    try:
        # i18n: "rev" is a keyword
        l = int(getstring(l[0], _("rev requires a number")))
    except ValueError:
        # i18n: "rev" is a keyword
        raise error.ParseError(_("rev expects a number"))
    return [r for r in subset if r == l]

def reverse(repo, subset, x):
    """``reverse(set)``
    Reverse order of set.
    """
    l = getset(repo, subset, x)
    l.reverse()
    return l

def roots(repo, subset, x):
    """``roots(set)``
    Changesets with no parent changeset in set.
    """
    s = getset(repo, subset, x)
    cs = set(children(repo, subset, x))
    return [r for r in s if r not in cs]

def sort(repo, subset, x):
    """``sort(set[, [-]key...])``
    Sort set by keys. The default sort order is ascending, specify a key
    as ``-key`` to sort in descending order.

    The keys can be:

    - ``rev`` for the revision number,
    - ``branch`` for the branch name,
    - ``desc`` for the commit message (description),
    - ``user`` for user name (``author`` can be used as an alias),
    - ``date`` for the commit date
    """
    # i18n: "sort" is a keyword
    l = getargs(x, 1, 2, _("sort requires one or two arguments"))
    keys = "rev"
    if len(l) == 2:
        keys = getstring(l[1], _("sort spec must be a string"))

    s = l[0]
    keys = keys.split()
    l = []
    def invert(s):
        return "".join(chr(255 - ord(c)) for c in s)
    for r in getset(repo, subset, s):
        c = repo[r]
        e = []
        for k in keys:
            if k == 'rev':
                e.append(r)
            elif k == '-rev':
                e.append(-r)
            elif k == 'branch':
                e.append(c.branch())
            elif k == '-branch':
                e.append(invert(c.branch()))
            elif k == 'desc':
                e.append(c.description())
            elif k == '-desc':
                e.append(invert(c.description()))
            elif k in 'user author':
                e.append(c.user())
            elif k in '-user -author':
                e.append(invert(c.user()))
            elif k == 'date':
                e.append(c.date()[0])
            elif k == '-date':
                e.append(-c.date()[0])
            else:
                raise error.ParseError(_("unknown sort key %r") % k)
        e.append(r)
        l.append(e)
    l.sort()
    return [e[-1] for e in l]

def tag(repo, subset, x):
    """``tag(name)``
    The specified tag by name, or all tagged revisions if no name is given.
    """
    # i18n: "tag" is a keyword
    args = getargs(x, 0, 1, _("tag takes one or no arguments"))
    cl = repo.changelog
    if args:
        tn = getstring(args[0],
                       # i18n: "tag" is a keyword
                       _('the argument to tag must be a string'))
        if not repo.tags().get(tn, None):
            raise util.Abort(_("tag '%s' does not exist") % tn)
        s = set([cl.rev(n) for t, n in repo.tagslist() if t == tn])
    else:
        s = set([cl.rev(n) for t, n in repo.tagslist() if t != 'tip'])
    return [r for r in subset if r in s]

def tagged(repo, subset, x):
    return tag(repo, subset, x)

def user(repo, subset, x):
    """``user(string)``
    User name is string.
    """
    return author(repo, subset, x)

symbols = {
    "adds": adds,
    "all": getall,
    "ancestor": ancestor,
    "ancestors": ancestors,
    "author": author,
    "bisected": bisected,
    "bookmark": bookmark,
    "branch": branch,
    "children": children,
    "closed": closed,
    "contains": contains,
    "date": date,
    "descendants": descendants,
    "file": hasfile,
    "follow": follow,
    "grep": grep,
    "head": head,
    "heads": heads,
    "keyword": keyword,
    "last": last,
    "limit": limit,
    "max": maxrev,
    "min": minrev,
    "merge": merge,
    "modifies": modifies,
    "id": node,
    "outgoing": outgoing,
    "p1": p1,
    "p2": p2,
    "parents": parents,
    "present": present,
    "removes": removes,
    "reverse": reverse,
    "rev": rev,
    "roots": roots,
    "sort": sort,
    "tag": tag,
    "tagged": tagged,
    "user": user,
}

methods = {
    "range": rangeset,
    "string": stringset,
    "symbol": symbolset,
    "and": andset,
    "or": orset,
    "not": notset,
    "list": listset,
    "func": func,
    "ancestor": ancestorspec,
    "parent": parentspec,
    "parentpost": p1,
}

def optimize(x, small):
    if x is None:
        return 0, x

    smallbonus = 1
    if small:
        smallbonus = .5

    op = x[0]
    if op == 'minus':
        return optimize(('and', x[1], ('not', x[2])), small)
    elif op == 'dagrange':
        return optimize(('and', ('func', ('symbol', 'descendants'), x[1]),
                         ('func', ('symbol', 'ancestors'), x[2])), small)
    elif op == 'dagrangepre':
        return optimize(('func', ('symbol', 'ancestors'), x[1]), small)
    elif op == 'dagrangepost':
        return optimize(('func', ('symbol', 'descendants'), x[1]), small)
    elif op == 'rangepre':
        return optimize(('range', ('string', '0'), x[1]), small)
    elif op == 'rangepost':
        return optimize(('range', x[1], ('string', 'tip')), small)
    elif op == 'negate':
        return optimize(('string',
                         '-' + getstring(x[1], _("can't negate that"))), small)
    elif op in 'string symbol negate':
        return smallbonus, x # single revisions are small
    elif op == 'and' or op == 'dagrange':
        wa, ta = optimize(x[1], True)
        wb, tb = optimize(x[2], True)
        w = min(wa, wb)
        if wa > wb:
            return w, (op, tb, ta)
        return w, (op, ta, tb)
    elif op == 'or':
        wa, ta = optimize(x[1], False)
        wb, tb = optimize(x[2], False)
        if wb < wa:
            wb, wa = wa, wb
        return max(wa, wb), (op, ta, tb)
    elif op == 'not':
        o = optimize(x[1], not small)
        return o[0], (op, o[1])
    elif op == 'parentpost':
        o = optimize(x[1], small)
        return o[0], (op, o[1])
    elif op == 'group':
        return optimize(x[1], small)
    elif op in 'range list parent ancestorspec':
        wa, ta = optimize(x[1], small)
        wb, tb = optimize(x[2], small)
        return wa + wb, (op, ta, tb)
    elif op == 'func':
        f = getstring(x[1], _("not a symbol"))
        wa, ta = optimize(x[2], small)
        if f in "grep date user author keyword branch file outgoing closed":
            w = 10 # slow
        elif f in "modifies adds removes":
            w = 30 # slower
        elif f == "contains":
            w = 100 # very slow
        elif f == "ancestor":
            w = 1 * smallbonus
        elif f in "reverse limit":
            w = 0
        elif f in "sort":
            w = 10 # assume most sorts look at changelog
        else:
            w = 1
        return w + wa, (op, x[1], ta)
    return 1, x

class revsetalias(object):
    funcre = re.compile('^([^(]+)\(([^)]+)\)$')
    args = ()

    def __init__(self, token, value):
        '''Aliases like:

        h = heads(default)
        b($1) = ancestors($1) - ancestors(default)
        '''
        if isinstance(token, tuple):
            self.type, self.name = token
        else:
            m = self.funcre.search(token)
            if m:
                self.type = 'func'
                self.name = m.group(1)
                self.args = [x.strip() for x in m.group(2).split(',')]
            else:
                self.type = 'symbol'
                self.name = token

        if isinstance(value, str):
            for arg in self.args:
                value = value.replace(arg, repr(arg))
            self.replacement, pos = parse(value)
            if pos != len(value):
                raise error.ParseError('invalid token', pos)
        else:
            self.replacement = value

    def match(self, tree):
        if not tree:
            return False
        if tree == (self.type, self.name):
            return True
        if tree[0] != self.type:
            return False
        if len(tree) > 1 and tree[1] != ('symbol', self.name):
            return False
        # 'func' + funcname + args
        if ((self.args and len(tree) != 3) or
            (len(self.args) == 1 and tree[2][0] == 'list') or
            (len(self.args) > 1 and (tree[2][0] != 'list' or
                                     len(tree[2]) - 1 != len(self.args)))):
            raise error.ParseError('invalid amount of arguments', len(tree) - 2)
        return True

    def replace(self, tree):
        if tree == (self.type, self.name):
            return self.replacement
        result = self.replacement
        def getsubtree(i):
            if tree[2][0] == 'list':
                return tree[2][i + 1]
            return tree[i + 2]
        for i, v in enumerate(self.args):
            valalias = revsetalias(('string', v), getsubtree(i))
            result = valalias.process(result)
        return result

    def process(self, tree):
        if self.match(tree):
            return self.replace(tree)
        if isinstance(tree, tuple):
            return tuple(map(self.process, tree))
        return tree

def findaliases(ui, tree):
    for k, v in ui.configitems('revsetalias'):
        alias = revsetalias(k, v)
        tree = alias.process(tree)
    return tree

parse = parser.parser(tokenize, elements).parse

def match(ui, spec):
    if not spec:
        raise error.ParseError(_("empty query"))
    tree, pos = parse(spec)
    if (pos != len(spec)):
        raise error.ParseError("invalid token", pos)
    tree = findaliases(ui, tree)
    weight, tree = optimize(tree, True)
    def mfunc(repo, subset):
        return getset(repo, subset, tree)
    return mfunc

def makedoc(topic, doc):
    return help.makeitemsdoc(topic, doc, '.. predicatesmarker', symbols)

# tell hggettext to extract docstrings from these functions:
i18nfunctions = symbols.values()