mercurial/ancestor.py
author Alexis S. L. Carvalho <alexis@cecm.usp.br>
Sat, 10 Mar 2007 23:00:57 -0300
changeset 4190 e8ee8fdeddb1
parent 3673 eb0b4a2d70a9
permissions -rw-r--r--
change locate to use relglobs by default This makes its default behaviour useful again (issue108), and changes it search the entire repository by default (instead of just the cwd), just like all other commands. It also hides issue204 by default, but you'll still see the same behaviour if you give it a relpath: pattern.

# ancestor.py - generic DAG ancestor algorithm for mercurial
#
# Copyright 2006 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

import heapq

def ancestor(a, b, pfunc):
    """
    return the least common ancestor of nodes a and b or None if there
    is no such ancestor.

    pfunc must return a list of parent vertices
    """

    if a == b:
        return a

    # find depth from root of all ancestors
    visit = [a, b]
    depth = {}
    while visit:
        vertex = visit[-1]
        pl = pfunc(vertex)
        if not pl:
            depth[vertex] = 0
            visit.pop()
        else:
            for p in pl:
                if p == a or p == b: # did we find a or b as a parent?
                    return p # we're done
                if p not in depth:
                    visit.append(p)
            if visit[-1] == vertex:
                depth[vertex] = min([depth[p] for p in pl]) - 1
                visit.pop()

    # traverse ancestors in order of decreasing distance from root
    def ancestors(vertex):
        h = [(depth[vertex], vertex)]
        seen = {}
        while h:
            d, n = heapq.heappop(h)
            if n not in seen:
                seen[n] = 1
                yield (d, n)
                for p in pfunc(n):
                    heapq.heappush(h, (depth[p], p))

    def generations(vertex):
        sg, s = None, {}
        for g, v in ancestors(vertex):
            if g != sg:
                if sg:
                    yield sg, s
                sg, s = g, {v:1}
            else:
                s[v] = 1
        yield sg, s

    x = generations(a)
    y = generations(b)
    gx = x.next()
    gy = y.next()

    # increment each ancestor list until it is closer to root than
    # the other, or they match
    try:
        while 1:
            if gx[0] == gy[0]:
                for v in gx[1]:
                    if v in gy[1]:
                        return v
                gy = y.next()
                gx = x.next()
            elif gx[0] > gy[0]:
                gy = y.next()
            else:
                gx = x.next()
    except StopIteration:
        return None