mercurial/copies.py

copies: add docstring for mergecopies

# copies.py - copy detection for Mercurial
#
# Copyright 2008 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 util
import heapq

def _nonoverlap(d1, d2, d3):
    "Return list of elements in d1 not in d2 or d3"
    return sorted([d for d in d1 if d not in d3 and d not in d2])

def _dirname(f):
    s = f.rfind("/")
    if s == -1:
        return ""
    return f[:s]

def _dirs(files):
    d = set()
    for f in files:
        f = _dirname(f)
        while f not in d:
            d.add(f)
            f = _dirname(f)
    return d

def _findlimit(repo, a, b):
    """Find the earliest revision that's an ancestor of a or b but not both,
    None if no such revision exists.
    """
    # basic idea:
    # - mark a and b with different sides
    # - if a parent's children are all on the same side, the parent is
    #   on that side, otherwise it is on no side
    # - walk the graph in topological order with the help of a heap;
    #   - add unseen parents to side map
    #   - clear side of any parent that has children on different sides
    #   - track number of interesting revs that might still be on a side
    #   - track the lowest interesting rev seen
    #   - quit when interesting revs is zero

    cl = repo.changelog
    working = len(cl) # pseudo rev for the working directory
    if a is None:
        a = working
    if b is None:
        b = working

    side = {a: -1, b: 1}
    visit = [-a, -b]
    heapq.heapify(visit)
    interesting = len(visit)
    hascommonancestor = False
    limit = working

    while interesting:
        r = -heapq.heappop(visit)
        if r == working:
            parents = [cl.rev(p) for p in repo.dirstate.parents()]
        else:
            parents = cl.parentrevs(r)
        for p in parents:
            if p < 0:
                continue
            if p not in side:
                # first time we see p; add it to visit
                side[p] = side[r]
                if side[p]:
                    interesting += 1
                heapq.heappush(visit, -p)
            elif side[p] and side[p] != side[r]:
                # p was interesting but now we know better
                side[p] = 0
                interesting -= 1
                hascommonancestor = True
        if side[r]:
            limit = r # lowest rev visited
            interesting -= 1

    if not hascommonancestor:
        return None
    return limit

def _chain(src, dst, a, b):
    '''chain two sets of copies a->b'''
    t = a.copy()
    for k, v in b.iteritems():
        if v in t:
            # found a chain
            if t[v] != k:
                # file wasn't renamed back to itself
                t[k] = t[v]
            if v not in dst:
                # chain was a rename, not a copy
                del t[v]
        if v in src:
            # file is a copy of an existing file
            t[k] = v

    # remove criss-crossed copies
    for k, v in t.items():
        if k in src and v in dst:
            del t[k]

    return t

def _tracefile(fctx, actx):
    '''return file context that is the ancestor of fctx present in actx'''
    stop = actx.rev()
    am = actx.manifest()

    for f in fctx.ancestors():
        if am.get(f.path(), None) == f.filenode():
            return f
        if f.rev() < stop:
            return None

def _dirstatecopies(d):
    ds = d._repo.dirstate
    c = ds.copies().copy()
    for k in c.keys():
        if ds[k] not in 'anm':
            del c[k]
    return c

def _forwardcopies(a, b):
    '''find {dst@b: src@a} copy mapping where a is an ancestor of b'''

    # check for working copy
    w = None
    if b.rev() is None:
        w = b
        b = w.p1()
        if a == b:
            # short-circuit to avoid issues with merge states
            return _dirstatecopies(w)

    # find where new files came from
    # we currently don't try to find where old files went, too expensive
    # this means we can miss a case like 'hg rm b; hg cp a b'
    cm = {}
    for f in b:
        if f not in a:
            ofctx = _tracefile(b[f], a)
            if ofctx:
                cm[f] = ofctx.path()

    # combine copies from dirstate if necessary
    if w is not None:
        cm = _chain(a, w, cm, _dirstatecopies(w))

    return cm

def _backwardcopies(a, b):
    # because the forward mapping is 1:n, we can lose renames here
    # in particular, we find renames better than copies
    f = _forwardcopies(b, a)
    r = {}
    for k, v in f.iteritems():
        r[v] = k
    return r

def pathcopies(x, y):
    '''find {dst@y: src@x} copy mapping for directed compare'''
    if x == y or not x or not y:
        return {}
    a = y.ancestor(x)
    if a == x:
        return _forwardcopies(x, y)
    if a == y:
        return _backwardcopies(x, y)
    return _chain(x, y, _backwardcopies(x, a), _forwardcopies(a, y))

def mergecopies(repo, c1, c2, ca, checkdirs=True):
    """
    Find moves and copies between context c1 and c2 that are relevant
    for merging.

    Returns two dicts, "copy" and "diverge".

    "copy" is a mapping from source name -> destination name,
    where source is in c1 and destination is in c2 or vice-versa.

    "diverge" is a mapping of source name -> list of destination names
    for divergent renames.
    """
    # avoid silly behavior for update from empty dir
    if not c1 or not c2 or c1 == c2:
        return {}, {}

    # avoid silly behavior for parent -> working dir
    if c2.node() is None and c1.node() == repo.dirstate.p1():
        return repo.dirstate.copies(), {}

    limit = _findlimit(repo, c1.rev(), c2.rev())
    if limit is None:
        # no common ancestor, no copies
        return {}, {}
    m1 = c1.manifest()
    m2 = c2.manifest()
    ma = ca.manifest()

    def makectx(f, n):
        if len(n) != 20: # in a working context?
            if c1.rev() is None:
                return c1.filectx(f)
            return c2.filectx(f)
        return repo.filectx(f, fileid=n)

    ctx = util.lrucachefunc(makectx)
    copy = {}
    fullcopy = {}
    diverge = {}

    def related(f1, f2, limit):
        # Walk back to common ancestor to see if the two files originate
        # from the same file. Since workingfilectx's rev() is None it messes
        # up the integer comparison logic, hence the pre-step check for
        # None (f1 and f2 can only be workingfilectx's initially).

        if f1 == f2:
            return f1 # a match

        g1, g2 = f1.ancestors(), f2.ancestors()
        try:
            f1r, f2r = f1.rev(), f2.rev()

            if f1r is None:
                f1 = g1.next()
            if f2r is None:
                f2 = g2.next()

            while True:
                f1r, f2r = f1.rev(), f2.rev()
                if f1r > f2r:
                    f1 = g1.next()
                elif f2r > f1r:
                    f2 = g2.next()
                elif f1 == f2:
                    return f1 # a match
                elif f1r == f2r or f1r < limit or f2r < limit:
                    return False # copy no longer relevant
        except StopIteration:
            return False

    def checkcopies(f, m1, m2):
        '''check possible copies of f from m1 to m2'''
        of = None
        seen = set([f])
        for oc in ctx(f, m1[f]).ancestors():
            ocr = oc.rev()
            of = oc.path()
            if of in seen:
                # check limit late - grab last rename before
                if ocr < limit:
                    break
                continue
            seen.add(of)

            fullcopy[f] = of # remember for dir rename detection
            if of not in m2:
                continue # no match, keep looking
            if m2[of] == ma.get(of):
                break # no merge needed, quit early
            c2 = ctx(of, m2[of])
            cr = related(oc, c2, ca.rev())
            if cr and (of == f or of == c2.path()): # non-divergent
                copy[f] = of
                of = None
                break

        if of in ma:
            diverge.setdefault(of, []).append(f)

    repo.ui.debug("  searching for copies back to rev %d\n" % limit)

    u1 = _nonoverlap(m1, m2, ma)
    u2 = _nonoverlap(m2, m1, ma)

    if u1:
        repo.ui.debug("  unmatched files in local:\n   %s\n"
                      % "\n   ".join(u1))
    if u2:
        repo.ui.debug("  unmatched files in other:\n   %s\n"
                      % "\n   ".join(u2))

    for f in u1:
        checkcopies(f, m1, m2)
    for f in u2:
        checkcopies(f, m2, m1)

    diverge2 = set()
    for of, fl in diverge.items():
        if len(fl) == 1 or of in c2:
            del diverge[of] # not actually divergent, or not a rename
        else:
            diverge2.update(fl) # reverse map for below

    if fullcopy:
        repo.ui.debug("  all copies found (* = to merge, ! = divergent):\n")
        for f in fullcopy:
            note = ""
            if f in copy:
                note += "*"
            if f in diverge2:
                note += "!"
            repo.ui.debug("   %s -> %s %s\n" % (f, fullcopy[f], note))
    del diverge2

    if not fullcopy or not checkdirs:
        return copy, diverge

    repo.ui.debug("  checking for directory renames\n")

    # generate a directory move map
    d1, d2 = _dirs(m1), _dirs(m2)
    invalid = set()
    dirmove = {}

    # examine each file copy for a potential directory move, which is
    # when all the files in a directory are moved to a new directory
    for dst, src in fullcopy.iteritems():
        dsrc, ddst = _dirname(src), _dirname(dst)
        if dsrc in invalid:
            # already seen to be uninteresting
            continue
        elif dsrc in d1 and ddst in d1:
            # directory wasn't entirely moved locally
            invalid.add(dsrc)
        elif dsrc in d2 and ddst in d2:
            # directory wasn't entirely moved remotely
            invalid.add(dsrc)
        elif dsrc in dirmove and dirmove[dsrc] != ddst:
            # files from the same directory moved to two different places
            invalid.add(dsrc)
        else:
            # looks good so far
            dirmove[dsrc + "/"] = ddst + "/"

    for i in invalid:
        if i in dirmove:
            del dirmove[i]
    del d1, d2, invalid

    if not dirmove:
        return copy, diverge

    for d in dirmove:
        repo.ui.debug("  dir %s -> %s\n" % (d, dirmove[d]))

    # check unaccounted nonoverlapping files against directory moves
    for f in u1 + u2:
        if f not in fullcopy:
            for d in dirmove:
                if f.startswith(d):
                    # new file added in a directory that was moved, move it
                    df = dirmove[d] + f[len(d):]
                    if df not in copy:
                        copy[f] = df
                        repo.ui.debug("  file %s -> %s\n" % (f, copy[f]))
                    break

    return copy, diverge