comparison mercurial/copies.py @ 42222:57203e0210f8

copies: calculate mergecopies() based on pathcopies()

When copies are stored in changesets, we need a changeset-centric
version of mergecopies() just like we have a changeset-centric version
of pathcopies(). I think the natural way of thinking about
mergecopies() is in terms of pathcopies() from the base to each of the
commits. So if we can rewrite mergecopies() based on two such
pathcopies() calls, we'll get the changeset-centric version for
free. That's what this patch does.

A nice bonus is that it ends up being a lot simpler. mergecopies() has
accumulated a lot of technical debt over time. One good example is the
code for dealing with grafts (the "partial/incomplete/dirty"
stuff). Since pathcopies() already deals with backwards renames and
ping-pong renames, we get that for free.

I've run tests with hard-coded debug logging for "fullcopy" and while
I haven't looked at every difference it produces, all the ones I have
looked at seemed reasonable to me. I'm a little surprised that no more
tests fail when run with '--extra-config-opt
experimental.copies.read-from=compatibility' compared to before this
patch. This patch also fixes the broken cases in test-annotate.t and
test-fastannotate.t. It also enables the part of test-copies.t that
was previously disabled exactly because mergecopies() needed to get a
changeset-centric version.

One drawback of the rewritten code is that we may now make
remotefilelog prefetch more files. We used to prefetch files that were
unique to either side of the merge compared to the other. We now
prefetch files that are unique to either side of the merge compared to
the base. This means that if you added the same file to each side, we
would not prefetch it before, but we would now. Such cases are
probably quite rare, but one likely scenario where they happen is when
moving from a commit to its successor (or the other way around). The
user will probably already have the files in the cache in such cases,
so it's probably not a big deal.

Some timings for calculating mergecopies between two revisions
(revisions shown on each line, all using the common ancestor as base):

In the hg repo:
4.8 4.9: 0.21s -> 0.21s
4.0 4.8: 0.35s -> 0.63s

In and old copy of the mozilla-unified repo:
FIREFOX_BETA_60_BASE^ FIREFOX_BETA_60_BASE: 0.82s -> 0.82s
FIREFOX_NIGHTLY_59_END FIREFOX_BETA_60_BASE: 2.5s -> 2.6s
FIREFOX_BETA_59_END FIREFOX_BETA_60_BASE: 3.9s -> 4.1s
FIREFOX_AURORA_50_BASE FIREFOX_BETA_60_BASE: 31s -> 33s

So it's measurably slower in most cases. The most significant
difference is in the hg repo between revisions 4.0 and 4.8. In that
case it seems to come from the fact that pathcopies() uses
fctx.isintroducedafter() (in _tracefile), while the old mergecopies()
used fctx.linkrev() (in _checkcopies()). That results in a single call
to filectx._adjustlinkrev(), which is responsible for the entire
difference in time (in my repo). So we pay a performance penalty but
we get more correct code (see change in
test-mv-cp-st-diff.t). Deleting the "== f.filenode()" in _tracefile()
recovers the lost performance in the hg repo.

There were are few other optimizations in _checkcopies() that I could
not measure any impact from. One was from the "seen" set. Another was
from a "continue" when the file was not in the destination manifest
(corresponding to "am" in _tracefile).

Also note that merge copies are not calculated when updating with a
clean working copy, which is probably the most common case. I
therefore think the much simpler code is worth the slowdown.

Differential Revision: https://phab.mercurial-scm.org/D6255

42221:c83c08cf02b7

        if u2:
            repo.ui.debug("%s:\n   %s\n" % (header % 'other', "\n   ".join(u2)))

    return u1, u2

def _makegetfctx(ctx):
    """return a 'getfctx' function suitable for _checkcopies usage

    We have to re-setup the function building 'filectx' for each
    '_checkcopies' to ensure the linkrev adjustment is properly setup for
    each. Linkrev adjustment is important to avoid bug in rename
    detection. Moreover, having a proper '_ancestrycontext' setup ensures
    the performance impact of this adjustment is kept limited. Without it,
    each file could do a full dag traversal making the time complexity of
    the operation explode (see issue4537).

    This function exists here mostly to limit the impact on stable. Feel
    free to refactor on default.
    """
    rev = ctx.rev()
    repo = ctx._repo
    ac = getattr(ctx, '_ancestrycontext', None)
    if ac is None:
        revs = [rev]
        if rev is None:
            revs = [p.rev() for p in ctx.parents()]
        ac = repo.changelog.ancestors(revs, inclusive=True)
        ctx._ancestrycontext = ac
    def makectx(f, n):
        if n in node.wdirfilenodeids:  # in a working context?
            if ctx.rev() is None:
                return ctx.filectx(f)
            return repo[None][f]
        fctx = repo.filectx(f, fileid=n)
        # setup only needed for filectx not create from a changectx
        fctx._ancestrycontext = ac
        fctx._descendantrev = rev
        return fctx
    return util.lrucachefunc(makectx)

def _combinecopies(copyfrom, copyto, finalcopy, diverge, incompletediverge):
    """combine partial copy paths"""
    remainder = {}
    for f in copyfrom:
        if f in copyto:
            finalcopy[copyto[f]] = copyfrom[f]
            del copyto[f]
    for f in incompletediverge:
        assert f not in diverge
        ic = incompletediverge[f]
        if ic[0] in copyto:
            diverge[f] = [copyto[ic[0]], ic[1]]
        else:
            remainder[f] = ic
    return remainder

def mergecopies(repo, c1, c2, base):
    """
    Finds moves and copies between context c1 and c2 that are relevant for
    merging. 'base' will be used as the merge base.

                                              'copytrace.sourcecommitlimit')
        commits = len(repo.revs('%d::%d', base.rev(), c1.rev()))
        return commits < sourcecommitlimit
    return False

def _fullcopytracing(repo, c1, c2, base):
    """ The full copytracing algorithm which finds all the new files that were
    added from merge base up to the top commit and for each file it checks if
    this file was copied from another file.

    This is pretty slow when a lot of changesets are involved but will track all
    the copies.
    """
    # In certain scenarios (e.g. graft, update or rebase), base can be
    # overridden We still need to know a real common ancestor in this case We
    # can't just compute _c1.ancestor(_c2) and compare it to ca, because there
    # can be multiple common ancestors, e.g. in case of bidmerge.  Because our
    # caller may not know if the revision passed in lieu of the CA is a genuine
    # common ancestor or not without explicitly checking it, it's better to
    # determine that here.
    #
    # base.isancestorof(wc) is False, work around that
    _c1 = c1.p1() if c1.rev() is None else c1
    _c2 = c2.p1() if c2.rev() is None else c2
    # an endpoint is "dirty" if it isn't a descendant of the merge base
    # if we have a dirty endpoint, we need to trigger graft logic, and also
    # keep track of which endpoint is dirty
    dirtyc1 = not base.isancestorof(_c1)
    dirtyc2 = not base.isancestorof(_c2)
    graft = dirtyc1 or dirtyc2
    tca = base
    if graft:
        tca = _c1.ancestor(_c2)

    limit = _findlimit(repo, c1, c2)

    m1 = c1.manifest()
    m2 = c2.manifest()
    mb = base.manifest()

    # gather data from _checkcopies:
    # - diverge = record all diverges in this dict
    # - copy = record all non-divergent copies in this dict
    # - fullcopy = record all copies in this dict
    # - incomplete = record non-divergent partial copies here
    # - incompletediverge = record divergent partial copies here
    diverge = {} # divergence data is shared
    incompletediverge  = {}
    data1 = {'copy': {},
             'fullcopy': {},
             'incomplete': {},
             'diverge': diverge,
             'incompletediverge': incompletediverge,
            }
    data2 = {'copy': {},
             'fullcopy': {},
             'incomplete': {},
             'diverge': diverge,
             'incompletediverge': incompletediverge,
            }

    # find interesting file sets from manifests
    addedinm1 = m1.filesnotin(mb, repo.narrowmatch())
    addedinm2 = m2.filesnotin(mb, repo.narrowmatch())
    bothnew = sorted(addedinm1 & addedinm2)
    if tca == base:
        # unmatched file from base
        u1r, u2r = _computenonoverlap(repo, c1, c2, addedinm1, addedinm2)
        u1u, u2u = u1r, u2r
    else:
        # unmatched file from base (DAG rotation in the graft case)
        u1r, u2r = _computenonoverlap(repo, c1, c2, addedinm1, addedinm2)
        # unmatched file from topological common ancestors (no DAG rotation)
        # need to recompute this for directory move handling when grafting
        mta = tca.manifest()
        u1u, u2u = _computenonoverlap(repo, c1, c2,
                                      m1.filesnotin(mta, repo.narrowmatch()),
                                      m2.filesnotin(mta, repo.narrowmatch()),
                                      debug=False)

    for f in u1u:
        _checkcopies(c1, c2, f, base, tca, dirtyc1, limit, data1)

    for f in u2u:
        _checkcopies(c2, c1, f, base, tca, dirtyc2, limit, data2)

    copy = dict(data1['copy'])
    copy.update(data2['copy'])
    fullcopy = dict(data1['fullcopy'])
    fullcopy.update(data2['fullcopy'])

    if dirtyc1:
        _combinecopies(data2['incomplete'], data1['incomplete'], copy, diverge,
                       incompletediverge)
    if dirtyc2:
        _combinecopies(data1['incomplete'], data2['incomplete'], copy, diverge,
                       incompletediverge)

    renamedelete = {}
    renamedeleteset = set()
    divergeset = set()
    for of, fl in list(diverge.items()):
        if len(fl) == 1 or of in c1 or of in c2:
            del diverge[of] # not actually divergent, or not a rename
            if of not in c1 and of not in c2:
                # renamed on one side, deleted on the other side, but filter
                # out files that have been renamed and then deleted
                renamedelete[of] = [f for f in fl if f in c1 or f in c2]
                renamedeleteset.update(fl) # reverse map for below
        else:
            divergeset.update(fl) # reverse map for below

    bothdiverge = {}
    bothincompletediverge = {}
    remainder = {}
    both1 = {'copy': {},
             'fullcopy': {},
             'incomplete': {},
             'diverge': bothdiverge,
             'incompletediverge': bothincompletediverge
            }
    both2 = {'copy': {},
             'fullcopy': {},
             'incomplete': {},
             'diverge': bothdiverge,
             'incompletediverge': bothincompletediverge
            }
    for f in bothnew:
        _checkcopies(c1, c2, f, base, tca, dirtyc1, limit, both1)
        _checkcopies(c2, c1, f, base, tca, dirtyc2, limit, both2)
    if dirtyc1 and dirtyc2:
        remainder = _combinecopies(both2['incomplete'], both1['incomplete'],
                                   copy, bothdiverge, bothincompletediverge)
        remainder1 = _combinecopies(both1['incomplete'], both2['incomplete'],
                                   copy, bothdiverge, bothincompletediverge)
        remainder.update(remainder1)
    elif dirtyc1:
        # incomplete copies may only be found on the "dirty" side for bothnew
        assert not both2['incomplete']
        remainder = _combinecopies({}, both1['incomplete'], copy, bothdiverge,
                                   bothincompletediverge)
    elif dirtyc2:
        assert not both1['incomplete']
        remainder = _combinecopies({}, both2['incomplete'], copy, bothdiverge,
                                   bothincompletediverge)
    else:
        # incomplete copies and divergences can't happen outside grafts
        assert not both1['incomplete']
        assert not both2['incomplete']
        assert not bothincompletediverge
    for f in remainder:
        assert f not in bothdiverge
        ic = remainder[f]
        if ic[0] in (m1 if dirtyc1 else m2):
            # backed-out rename on one side, but watch out for deleted files
            bothdiverge[f] = ic
    for of, fl in bothdiverge.items():
        if len(fl) == 2 and fl[0] == fl[1]:
            copy[fl[0]] = of # not actually divergent, just matching renames

    # Sometimes we get invalid copies here (the "and not remotebase" in
    # _checkcopies() seems suspicious). Filter them out.
    for dst, src in fullcopy.copy().items():
        if src not in mb:
            del fullcopy[dst]
    # Sometimes we forget to add entries from "copy" to "fullcopy", so fix
    # that up here
    for dst, src in copy.items():
        fullcopy[dst] = src
    # Sometimes we forget to add entries from "diverge" to "fullcopy", so fix
    # that up here
    for src, dsts in diverge.items():
        for dst in dsts:
            fullcopy[dst] = src

    if not fullcopy:
        return copy, {}, diverge, renamedelete, {}

    if repo.ui.debugflag:
        repo.ui.debug("  all copies found (* = to merge, ! = divergent, "

        repo.ui.debug("   discovered dir src: '%s' -> dst: '%s'\n" %
                      (d, dirmove[d]))

    movewithdir = {}
    # check unaccounted nonoverlapping files against directory moves
    for f in u1r + u2r:
        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):]

                f2 = next(g2)
            else: # f1 and f2 point to files in the same linkrev
                return f1 == f2 # true if they point to the same file
    except StopIteration:
        return False

def _checkcopies(srcctx, dstctx, f, base, tca, remotebase, limit, data):
    """
    check possible copies of f from msrc to mdst

    srcctx = starting context for f in msrc
    dstctx = destination context for f in mdst
    f = the filename to check (as in msrc)
    base = the changectx used as a merge base
    tca = topological common ancestor for graft-like scenarios
    remotebase = True if base is outside tca::srcctx, False otherwise
    limit = the rev number to not search beyond
    data = dictionary of dictionary to store copy data. (see mergecopies)

    note: limit is only an optimization, and provides no guarantee that
    irrelevant revisions will not be visited
    there is no easy way to make this algorithm stop in a guaranteed way
    once it "goes behind a certain revision".
    """

    msrc = srcctx.manifest()
    mdst = dstctx.manifest()
    mb = base.manifest()
    mta = tca.manifest()
    # Might be true if this call is about finding backward renames,
    # This happens in the case of grafts because the DAG is then rotated.
    # If the file exists in both the base and the source, we are not looking
    # for a rename on the source side, but on the part of the DAG that is
    # traversed backwards.
    #
    # In the case there is both backward and forward renames (before and after
    # the base) this is more complicated as we must detect a divergence.
    # We use 'backwards = False' in that case.
    backwards = not remotebase and base != tca and f in mb
    getsrcfctx = _makegetfctx(srcctx)
    getdstfctx = _makegetfctx(dstctx)

    if msrc[f] == mb.get(f) and not remotebase:
        # Nothing to merge
        return

    of = None
    seen = {f}
    for oc in getsrcfctx(f, msrc[f]).ancestors():
        of = oc.path()
        if of in seen:
            # check limit late - grab last rename before
            if oc.linkrev() < limit:
                break
            continue
        seen.add(of)

        # remember for dir rename detection
        if backwards:
            data['fullcopy'][of] = f # grafting backwards through renames
        else:
            data['fullcopy'][f] = of
        if of not in mdst:
            continue # no match, keep looking
        if mdst[of] == mb.get(of):
            return # no merge needed, quit early
        c2 = getdstfctx(of, mdst[of])
        # c2 might be a plain new file on added on destination side that is
        # unrelated to the droids we are looking for.
        cr = _related(oc, c2)
        if cr and (of == f or of == c2.path()): # non-divergent
            if backwards:
                data['copy'][of] = f
            elif of in mb:
                data['copy'][f] = of
            elif remotebase: # special case: a <- b <- a -> b "ping-pong" rename
                data['copy'][of] = f
                del data['fullcopy'][f]
                data['fullcopy'][of] = f
            else: # divergence w.r.t. graft CA on one side of topological CA
                for sf in seen:
                    if sf in mb:
                        assert sf not in data['diverge']
                        data['diverge'][sf] = [f, of]
                        break
            return

    if of in mta:
        if backwards or remotebase:
            data['incomplete'][of] = f
        else:
            for sf in seen:
                if sf in mb:
                    if tca == base:
                        data['diverge'].setdefault(sf, []).append(f)
                    else:
                        data['incompletediverge'][sf] = [of, f]
                    return

def duplicatecopies(repo, wctx, rev, fromrev, skiprev=None):
    """reproduce copies from fromrev to rev in the dirstate

    If skiprev is specified, it's a revision that should be used to

42222:57203e0210f8

        if u2:
            repo.ui.debug("%s:\n   %s\n" % (header % 'other', "\n   ".join(u2)))

    return u1, u2

def mergecopies(repo, c1, c2, base):
    """
    Finds moves and copies between context c1 and c2 that are relevant for
    merging. 'base' will be used as the merge base.

                                              'copytrace.sourcecommitlimit')
        commits = len(repo.revs('%d::%d', base.rev(), c1.rev()))
        return commits < sourcecommitlimit
    return False

def _checksinglesidecopies(src, dsts1, m1, m2, mb, c2, base,
                           copy, renamedelete):
    if src not in m2:
        # deleted on side 2
        if src not in m1:
            # renamed on side 1, deleted on side 2
            renamedelete[src] = dsts1
    elif m2[src] != mb[src]:
        if not _related(c2[src], base[src]):
            return
        # modified on side 2
        for dst in dsts1:
            if dst not in m2:
                # dst not added on side 2 (handle as regular
                # "both created" case in manifestmerge otherwise)
                copy[dst] = src

def _fullcopytracing(repo, c1, c2, base):
    """ The full copytracing algorithm which finds all the new files that were
    added from merge base up to the top commit and for each file it checks if
    this file was copied from another file.

    This is pretty slow when a lot of changesets are involved but will track all
    the copies.
    """
    m1 = c1.manifest()
    m2 = c2.manifest()
    mb = base.manifest()

    copies1 = pathcopies(base, c1)
    copies2 = pathcopies(base, c2)

    inversecopies1 = {}
    inversecopies2 = {}
    for dst, src in copies1.items():
        inversecopies1.setdefault(src, []).append(dst)
    for dst, src in copies2.items():
        inversecopies2.setdefault(src, []).append(dst)

    copy = {}
    diverge = {}
    renamedelete = {}
    allsources = set(inversecopies1) | set(inversecopies2)
    for src in allsources:
        dsts1 = inversecopies1.get(src)
        dsts2 = inversecopies2.get(src)
        if dsts1 and dsts2:
            # copied/renamed on both sides
            if src not in m1 and src not in m2:
                # renamed on both sides
                dsts1 = set(dsts1)
                dsts2 = set(dsts2)
                # If there's some overlap in the rename destinations, we
                # consider it not divergent. For example, if side 1 copies 'a'
                # to 'b' and 'c' and deletes 'a', and side 2 copies 'a' to 'c'
                # and 'd' and deletes 'a'.
                if dsts1 & dsts2:
                    for dst in (dsts1 & dsts2):
                        copy[dst] = src
                else:
                    diverge[src] = sorted(dsts1 | dsts2)
            elif src in m1 and src in m2:
                # copied on both sides
                dsts1 = set(dsts1)
                dsts2 = set(dsts2)
                for dst in (dsts1 & dsts2):
                    copy[dst] = src
            # TODO: Handle cases where it was renamed on one side and copied
            # on the other side
        elif dsts1:
            # copied/renamed only on side 1
            _checksinglesidecopies(src, dsts1, m1, m2, mb, c2, base,
                                   copy, renamedelete)
        elif dsts2:
            # copied/renamed only on side 2
            _checksinglesidecopies(src, dsts2, m2, m1, mb, c1, base,
                                   copy, renamedelete)

    renamedeleteset = set()
    divergeset = set()
    for src, dsts in diverge.items():
        divergeset.update(dsts)
    for src, dsts in renamedelete.items():
        renamedeleteset.update(dsts)

    # find interesting file sets from manifests
    addedinm1 = m1.filesnotin(mb, repo.narrowmatch())
    addedinm2 = m2.filesnotin(mb, repo.narrowmatch())
    u1, u2 = _computenonoverlap(repo, c1, c2, addedinm1, addedinm2)

    fullcopy = copies1.copy()
    fullcopy.update(copies2)
    if not fullcopy:
        return copy, {}, diverge, renamedelete, {}

    if repo.ui.debugflag:
        repo.ui.debug("  all copies found (* = to merge, ! = divergent, "

        repo.ui.debug("   discovered dir src: '%s' -> dst: '%s'\n" %
                      (d, dirmove[d]))

    movewithdir = {}
    # 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):]

                f2 = next(g2)
            else: # f1 and f2 point to files in the same linkrev
                return f1 == f2 # true if they point to the same file
    except StopIteration:
        return False

def duplicatecopies(repo, wctx, rev, fromrev, skiprev=None):
    """reproduce copies from fromrev to rev in the dirstate

    If skiprev is specified, it's a revision that should be used to