Application: gvSIG desktop » gvSIG scripting

# diff_tree.py -- Utilities for diffing files and trees.

# Copyright (C) 2010 Google, Inc.

#

# Dulwich is dual-licensed under the Apache License, Version 2.0 and the GNU

# General Public License as public by the Free Software Foundation; version 2.0

# or (at your option) any later version. You can redistribute it and/or

# modify it under the terms of either of these two licenses.

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

#

# You should have received a copy of the licenses; if not, see

# <http://www.gnu.org/licenses/> for a copy of the GNU General Public License

# and <http://www.apache.org/licenses/LICENSE-2.0> for a copy of the Apache

# License, Version 2.0.

#

"""Utilities for diffing files and trees."""

import sys

from collections import (

    defaultdict,

    namedtuple,

    )

from io import BytesIO

from itertools import chain

import stat

from dulwich.objects import (

    S_ISGITLINK,

    TreeEntry,

    )

# TreeChange type constants.

CHANGE_ADD = 'add'

CHANGE_MODIFY = 'modify'

CHANGE_DELETE = 'delete'

CHANGE_RENAME = 'rename'

CHANGE_COPY = 'copy'

CHANGE_UNCHANGED = 'unchanged'

RENAME_CHANGE_TYPES = (CHANGE_RENAME, CHANGE_COPY)

_NULL_ENTRY = TreeEntry(None, None, None)

_MAX_SCORE = 100

RENAME_THRESHOLD = 60

MAX_FILES = 200

REWRITE_THRESHOLD = None

class TreeChange(namedtuple('TreeChange', ['type', 'old', 'new'])):

    """Named tuple a single change between two trees."""

    @classmethod

    def add(cls, new):

        return cls(CHANGE_ADD, _NULL_ENTRY, new)

    @classmethod

    def delete(cls, old):

        return cls(CHANGE_DELETE, old, _NULL_ENTRY)

def _tree_entries(path, tree):

    result = []

    if not tree:

        return result

    for entry in tree.iteritems(name_order=True):

        result.append(entry.in_path(path))

    return result

def _merge_entries(path, tree1, tree2):

    """Merge the entries of two trees.

    :param path: A path to prepend to all tree entry names.

    :param tree1: The first Tree object to iterate, or None.

    :param tree2: The second Tree object to iterate, or None.

    :return: A list of pairs of TreeEntry objects for each pair of entries in

        the trees. If an entry exists in one tree but not the other, the other

        entry will have all attributes set to None. If neither entry's path is

        None, they are guaranteed to match.

    """

    entries1 = _tree_entries(path, tree1)

    entries2 = _tree_entries(path, tree2)

    i1 = i2 = 0

    len1 = len(entries1)

    len2 = len(entries2)

    result = []

    while i1 < len1 and i2 < len2:

        entry1 = entries1[i1]

        entry2 = entries2[i2]

        if entry1.path < entry2.path:

            result.append((entry1, _NULL_ENTRY))

            i1 += 1

        elif entry1.path > entry2.path:

            result.append((_NULL_ENTRY, entry2))

            i2 += 1

        else:

            result.append((entry1, entry2))

            i1 += 1

            i2 += 1

    for i in range(i1, len1):

        result.append((entries1[i], _NULL_ENTRY))

    for i in range(i2, len2):

        result.append((_NULL_ENTRY, entries2[i]))

    return result

def _is_tree(entry):

    mode = entry.mode

    if mode is None:

        return False

    return stat.S_ISDIR(mode)

def walk_trees(store, tree1_id, tree2_id, prune_identical=False):

    """Recursively walk all the entries of two trees.

    Iteration is depth-first pre-order, as in e.g. os.walk.

    :param store: An ObjectStore for looking up objects.

    :param tree1_id: The SHA of the first Tree object to iterate, or None.

    :param tree2_id: The SHA of the second Tree object to iterate, or None.

    :param prune_identical: If True, identical subtrees will not be walked.

    :return: Iterator over Pairs of TreeEntry objects for each pair of entries

        in the trees and their subtrees recursively. If an entry exists in one

        tree but not the other, the other entry will have all attributes set

        to None. If neither entry's path is None, they are guaranteed to

        match.

    """

    # This could be fairly easily generalized to >2 trees if we find a use

    # case.

    mode1 = tree1_id and stat.S_IFDIR or None

    mode2 = tree2_id and stat.S_IFDIR or None

    todo = [(TreeEntry(b'', mode1, tree1_id), TreeEntry(b'', mode2, tree2_id))]

    while todo:

        entry1, entry2 = todo.pop()

        is_tree1 = _is_tree(entry1)

        is_tree2 = _is_tree(entry2)

        if prune_identical and is_tree1 and is_tree2 and entry1 == entry2:

            continue

        tree1 = is_tree1 and store[entry1.sha] or None

        tree2 = is_tree2 and store[entry2.sha] or None

        path = entry1.path or entry2.path

        todo.extend(reversed(_merge_entries(path, tree1, tree2)))

        yield entry1, entry2

def _skip_tree(entry):

    if entry.mode is None or stat.S_ISDIR(entry.mode):

        return _NULL_ENTRY

    return entry

def tree_changes(store, tree1_id, tree2_id, want_unchanged=False,

                 rename_detector=None):

    """Find the differences between the contents of two trees.

    :param store: An ObjectStore for looking up objects.

    :param tree1_id: The SHA of the source tree.

    :param tree2_id: The SHA of the target tree.

    :param want_unchanged: If True, include TreeChanges for unmodified entries

        as well.

    :param rename_detector: RenameDetector object for detecting renames.

    :return: Iterator over TreeChange instances for each change between the

        source and target tree.

    """

    if (rename_detector is not None and tree1_id is not None and

        tree2_id is not None):

        for change in rename_detector.changes_with_renames(

            tree1_id, tree2_id, want_unchanged=want_unchanged):

                yield change

        return

    entries = walk_trees(store, tree1_id, tree2_id,

                         prune_identical=(not want_unchanged))

    for entry1, entry2 in entries:

        if entry1 == entry2 and not want_unchanged:

            continue

        # Treat entries for trees as missing.

        entry1 = _skip_tree(entry1)

        entry2 = _skip_tree(entry2)

        if entry1 != _NULL_ENTRY and entry2 != _NULL_ENTRY:

            if stat.S_IFMT(entry1.mode) != stat.S_IFMT(entry2.mode):

                # File type changed: report as delete/add.

                yield TreeChange.delete(entry1)

                entry1 = _NULL_ENTRY

                change_type = CHANGE_ADD

            elif entry1 == entry2:

                change_type = CHANGE_UNCHANGED

            else:

                change_type = CHANGE_MODIFY

        elif entry1 != _NULL_ENTRY:

            change_type = CHANGE_DELETE

        elif entry2 != _NULL_ENTRY:

            change_type = CHANGE_ADD

        else:

            # Both were None because at least one was a tree.

            continue

        yield TreeChange(change_type, entry1, entry2)

def _all_eq(seq, key, value):

    for e in seq:

        if key(e) != value:

            return False

    return True

def _all_same(seq, key):

    return _all_eq(seq[1:], key, key(seq[0]))

def tree_changes_for_merge(store, parent_tree_ids, tree_id,

                           rename_detector=None):

    """Get the tree changes for a merge tree relative to all its parents.

    :param store: An ObjectStore for looking up objects.

    :param parent_tree_ids: An iterable of the SHAs of the parent trees.

    :param tree_id: The SHA of the merge tree.

    :param rename_detector: RenameDetector object for detecting renames.

    :return: Iterator over lists of TreeChange objects, one per conflicted path

        in the merge.

        Each list contains one element per parent, with the TreeChange for that

        path relative to that parent. An element may be None if it never

        existed in one parent and was deleted in two others.

        A path is only included in the output if it is a conflict, i.e. its SHA

        in the merge tree is not found in any of the parents, or in the case of

        deletes, if not all of the old SHAs match.

    """

    all_parent_changes = [tree_changes(store, t, tree_id,

                                       rename_detector=rename_detector)

                          for t in parent_tree_ids]

    num_parents = len(parent_tree_ids)

    changes_by_path = defaultdict(lambda: [None] * num_parents)

    # Organize by path.

    for i, parent_changes in enumerate(all_parent_changes):

        for change in parent_changes:

            if change.type == CHANGE_DELETE:

                path = change.old.path

            else:

                path = change.new.path

            changes_by_path[path][i] = change

    old_sha = lambda c: c.old.sha

    change_type = lambda c: c.type

    # Yield only conflicting changes.

    for _, changes in sorted(changes_by_path.items()):

        assert len(changes) == num_parents

        have = [c for c in changes if c is not None]

        if _all_eq(have, change_type, CHANGE_DELETE):

            if not _all_same(have, old_sha):

                yield changes

        elif not _all_same(have, change_type):

            yield changes

        elif None not in changes:

            # If no change was found relative to one parent, that means the SHA

            # must have matched the SHA in that parent, so it is not a

            # conflict.

            yield changes

_BLOCK_SIZE = 64

def _count_blocks(obj):

    """Count the blocks in an object.

    Splits the data into blocks either on lines or <=64-byte chunks of lines.

    :param obj: The object to count blocks for.

    :return: A dict of block hashcode -> total bytes occurring.

    """

    block_counts = defaultdict(int)

    block = BytesIO()

    n = 0

    # Cache attrs as locals to avoid expensive lookups in the inner loop.

    block_write = block.write

    block_seek = block.seek

    block_truncate = block.truncate

    block_getvalue = block.getvalue

    for c in chain(*obj.as_raw_chunks()):

        if sys.version_info[0] == 3:

            c = c.to_bytes(1, 'big')

        block_write(c)

        n += 1

        if c == b'\n' or n == _BLOCK_SIZE:

            value = block_getvalue()

            block_counts[hash(value)] += len(value)

            block_seek(0)

            block_truncate()

            n = 0

    if n > 0:

        last_block = block_getvalue()

        block_counts[hash(last_block)] += len(last_block)

    return block_counts

def _common_bytes(blocks1, blocks2):

    """Count the number of common bytes in two block count dicts.

    :param block1: The first dict of block hashcode -> total bytes.

    :param block2: The second dict of block hashcode -> total bytes.

    :return: The number of bytes in common between blocks1 and blocks2. This is

        only approximate due to possible hash collisions.

    """

    # Iterate over the smaller of the two dicts, since this is symmetrical.

    if len(blocks1) > len(blocks2):

        blocks1, blocks2 = blocks2, blocks1

    score = 0

    for block, count1 in blocks1.items():

        count2 = blocks2.get(block)

        if count2:

            score += min(count1, count2)

    return score

def _similarity_score(obj1, obj2, block_cache=None):

    """Compute a similarity score for two objects.

    :param obj1: The first object to score.

    :param obj2: The second object to score.

    :param block_cache: An optional dict of SHA to block counts to cache

        results between calls.

    :return: The similarity score between the two objects, defined as the

        number of bytes in common between the two objects divided by the

        maximum size, scaled to the range 0-100.

    """

    if block_cache is None:

        block_cache = {}

    if obj1.id not in block_cache:

        block_cache[obj1.id] = _count_blocks(obj1)

    if obj2.id not in block_cache:

        block_cache[obj2.id] = _count_blocks(obj2)

    common_bytes = _common_bytes(block_cache[obj1.id], block_cache[obj2.id])

    max_size = max(obj1.raw_length(), obj2.raw_length())

    if not max_size:

        return _MAX_SCORE

    return int(float(common_bytes) * _MAX_SCORE / max_size)

def _tree_change_key(entry):

    # Sort by old path then new path. If only one exists, use it for both keys.

    path1 = entry.old.path

    path2 = entry.new.path

    if path1 is None:

        path1 = path2

    if path2 is None:

        path2 = path1

    return (path1, path2)

class RenameDetector(object):

    """Object for handling rename detection between two trees."""

    def __init__(self, store, rename_threshold=RENAME_THRESHOLD,

                 max_files=MAX_FILES,

                 rewrite_threshold=REWRITE_THRESHOLD,

                 find_copies_harder=False):

        """Initialize the rename detector.

        :param store: An ObjectStore for looking up objects.

        :param rename_threshold: The threshold similarity score for considering

            an add/delete pair to be a rename/copy; see _similarity_score.

        :param max_files: The maximum number of adds and deletes to consider,

            or None for no limit. The detector is guaranteed to compare no more

            than max_files ** 2 add/delete pairs. This limit is provided because

            rename detection can be quadratic in the project size. If the limit

            is exceeded, no content rename detection is attempted.

        :param rewrite_threshold: The threshold similarity score below which a

            modify should be considered a delete/add, or None to not break

            modifies; see _similarity_score.

        :param find_copies_harder: If True, consider unmodified files when

            detecting copies.

        """

        self._store = store

        self._rename_threshold = rename_threshold

        self._rewrite_threshold = rewrite_threshold

        self._max_files = max_files

        self._find_copies_harder = find_copies_harder

        self._want_unchanged = False

    def _reset(self):

        self._adds = []

        self._deletes = []

        self._changes = []

    def _should_split(self, change):

        if (self._rewrite_threshold is None or change.type != CHANGE_MODIFY or

            change.old.sha == change.new.sha):

            return False

        old_obj = self._store[change.old.sha]

        new_obj = self._store[change.new.sha]

        return _similarity_score(old_obj, new_obj) < self._rewrite_threshold

    def _add_change(self, change):

        if change.type == CHANGE_ADD:

            self._adds.append(change)

        elif change.type == CHANGE_DELETE:

            self._deletes.append(change)

        elif self._should_split(change):

            self._deletes.append(TreeChange.delete(change.old))

            self._adds.append(TreeChange.add(change.new))

        elif ((self._find_copies_harder and change.type == CHANGE_UNCHANGED)

              or change.type == CHANGE_MODIFY):

            # Treat all modifies as potential deletes for rename detection,

            # but don't split them (to avoid spurious renames). Setting

            # find_copies_harder means we treat unchanged the same as

            # modified.

            self._deletes.append(change)

        else:

            self._changes.append(change)

    def _collect_changes(self, tree1_id, tree2_id):

        want_unchanged = self._find_copies_harder or self._want_unchanged

        for change in tree_changes(self._store, tree1_id, tree2_id,

                                   want_unchanged=want_unchanged):

            self._add_change(change)

    def _prune(self, add_paths, delete_paths):

        self._adds = [a for a in self._adds if a.new.path not in add_paths]

        self._deletes = [d for d in self._deletes

                         if d.old.path not in delete_paths]

    def _find_exact_renames(self):

        add_map = defaultdict(list)

        for add in self._adds:

            add_map[add.new.sha].append(add.new)

        delete_map = defaultdict(list)

        for delete in self._deletes:

            # Keep track of whether the delete was actually marked as a delete.

            # If not, it needs to be marked as a copy.

            is_delete = delete.type == CHANGE_DELETE

            delete_map[delete.old.sha].append((delete.old, is_delete))

        add_paths = set()

        delete_paths = set()

        for sha, sha_deletes in delete_map.items():

            sha_adds = add_map[sha]

            for (old, is_delete), new in zip(sha_deletes, sha_adds):

                if stat.S_IFMT(old.mode) != stat.S_IFMT(new.mode):

                    continue

                if is_delete:

                    delete_paths.add(old.path)

                add_paths.add(new.path)

                new_type = is_delete and CHANGE_RENAME or CHANGE_COPY

                self._changes.append(TreeChange(new_type, old, new))

            num_extra_adds = len(sha_adds) - len(sha_deletes)

            # TODO(dborowitz): Less arbitrary way of dealing with extra copies.

            old = sha_deletes[0][0]

            if num_extra_adds > 0:

                for new in sha_adds[-num_extra_adds:]:

                    add_paths.add(new.path)

                    self._changes.append(TreeChange(CHANGE_COPY, old, new))

        self._prune(add_paths, delete_paths)

    def _should_find_content_renames(self):

        return len(self._adds) * len(self._deletes) <= self._max_files ** 2

    def _rename_type(self, check_paths, delete, add):

        if check_paths and delete.old.path == add.new.path:

            # If the paths match, this must be a split modify, so make sure it

            # comes out as a modify.

            return CHANGE_MODIFY

        elif delete.type != CHANGE_DELETE:

            # If it's in deletes but not marked as a delete, it must have been

            # added due to find_copies_harder, and needs to be marked as a

            # copy.

            return CHANGE_COPY

        return CHANGE_RENAME

    def _find_content_rename_candidates(self):

        candidates = self._candidates = []

        # TODO: Optimizations:

        #  - Compare object sizes before counting blocks.

        #  - Skip if delete's S_IFMT differs from all adds.

        #  - Skip if adds or deletes is empty.

        # Match C git's behavior of not attempting to find content renames if

        # the matrix size exceeds the threshold.

        if not self._should_find_content_renames():

            return

        block_cache = {}

        check_paths = self._rename_threshold is not None

        for delete in self._deletes:

            if S_ISGITLINK(delete.old.mode):

                continue  # Git links don't exist in this repo.

            old_sha = delete.old.sha

            old_obj = self._store[old_sha]

            block_cache[old_sha] = _count_blocks(old_obj)

            for add in self._adds:

                if stat.S_IFMT(delete.old.mode) != stat.S_IFMT(add.new.mode):

                    continue

                new_obj = self._store[add.new.sha]

                score = _similarity_score(old_obj, new_obj,

                                          block_cache=block_cache)

                if score > self._rename_threshold:

                    new_type = self._rename_type(check_paths, delete, add)

                    rename = TreeChange(new_type, delete.old, add.new)

                    candidates.append((-score, rename))

    def _choose_content_renames(self):

        # Sort scores from highest to lowest, but keep names in ascending

        # order.

        self._candidates.sort()

        delete_paths = set()

        add_paths = set()

        for _, change in self._candidates:

            new_path = change.new.path

            if new_path in add_paths:

                continue

            old_path = change.old.path

            orig_type = change.type

            if old_path in delete_paths:

                change = TreeChange(CHANGE_COPY, change.old, change.new)

            # If the candidate was originally a copy, that means it came from a

            # modified or unchanged path, so we don't want to prune it.

            if orig_type != CHANGE_COPY:

                delete_paths.add(old_path)

            add_paths.add(new_path)

            self._changes.append(change)

        self._prune(add_paths, delete_paths)

    def _join_modifies(self):

        if self._rewrite_threshold is None:

            return

        modifies = {}

        delete_map = dict((d.old.path, d) for d in self._deletes)

        for add in self._adds:

            path = add.new.path

            delete = delete_map.get(path)

            if (delete is not None and

                stat.S_IFMT(delete.old.mode) == stat.S_IFMT(add.new.mode)):

                modifies[path] = TreeChange(CHANGE_MODIFY, delete.old, add.new)

        self._adds = [a for a in self._adds if a.new.path not in modifies]

        self._deletes = [a for a in self._deletes if a.new.path not in

                         modifies]

        self._changes += modifies.values()

    def _sorted_changes(self):

        result = []

        result.extend(self._adds)

        result.extend(self._deletes)

        result.extend(self._changes)

        result.sort(key=_tree_change_key)

        return result

    def _prune_unchanged(self):

        if self._want_unchanged:

            return

        self._deletes = [d for d in self._deletes if d.type != CHANGE_UNCHANGED]

    def changes_with_renames(self, tree1_id, tree2_id, want_unchanged=False):

        """Iterate TreeChanges between two tree SHAs, with rename detection."""

        self._reset()

        self._want_unchanged = want_unchanged

        self._collect_changes(tree1_id, tree2_id)

        self._find_exact_renames()

        self._find_content_rename_candidates()

        self._choose_content_renames()

        self._join_modifies()

        self._prune_unchanged()

        return self._sorted_changes()

# Hold on to the pure-python implementations for testing.

_is_tree_py = _is_tree

_merge_entries_py = _merge_entries

_count_blocks_py = _count_blocks

try:

    # Try to import C versions

    from dulwich._diff_tree import _is_tree, _merge_entries, _count_blocks

except ImportError:

    pass