comparison mercurial/copies.py @ 18136:f23dea2b296e

copies: do not track backward copies, only renames (issue3739)

The inverse of a rename is a rename, but the inverse of a copy is not a copy.
Presenting it as such -- in particular, stuffing it into the same dict as real
copies -- causes bugs because other code starts believing the inverse copies
are real.

The only test whose output changes is test-mv-cp-st-diff.t. When a backwards
status -C command is run where a copy is involved, the inverse copy (which was
hitherto presented as a real copy) is no longer displayed.

Keeping track of inverse copies is useful in some situations -- composability
of diffs, for example, since adding "a" followed by an inverse copy "b" to "a"
is equivalent to a rename "b" to "a". However, representing them would require
a more complex data structure than the same dict in which real copies are also
stored.

18135:a6fe1b9cc68f

    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'''

        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):
    """
    Find moves and copies between context c1 and c2 that are relevant
    for merging.

18136:f23dea2b296e

    if w is not None:
        cm = _chain(a, w, cm, _dirstatecopies(w))

    return cm

def _backwardrenames(a, b):
    # Even though we're not taking copies into account, 1:n rename situations
    # can still exist (e.g. hg cp a b; hg mv a c). In those cases we
    # arbitrarily pick one of the renames.
    f = _forwardcopies(b, a)
    r = {}
    for k, v in f.iteritems():
        # remove copies
        if v in a:
            continue
        r[v] = k
    return r

def pathcopies(x, y):
    '''find {dst@y: src@x} copy mapping for directed compare'''

        return {}
    a = y.ancestor(x)
    if a == x:
        return _forwardcopies(x, y)
    if a == y:
        return _backwardrenames(x, y)
    return _chain(x, y, _backwardrenames(x, a), _forwardcopies(a, y))

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