comparison mercurial/metadata.py @ 45668:47ad23549b81

changing-files: add clean computation of changed file for merges

This is "a tad more complicated" than the previous cases. See inline
documentation for details (have fun).

Differential Revision: https://phab.mercurial-scm.org/D9128

45667:0303fc1f43f8

# metadata.py -- code related to various metadata computation and access.
#
# Copyright 2019 Google, Inc <[e-mail]>
# Copyright 2020 Pierre-Yves David <[e-mail]>
#

        # In the wild, one can encounter changeset where p1 is null but p2 is not
        return _process_linear(p1, ctx, parent=2)
    elif p1.rev() == p2.rev():
        # In the wild, one can encounter such "non-merge"
        return _process_linear(p1, ctx)
    filescopies = computechangesetcopies(ctx)
    filesadded = computechangesetfilesadded(ctx)
    filesremoved = computechangesetfilesremoved(ctx)
    filesmerged = computechangesetfilesmerged(ctx)
    files = ChangingFiles()
    files.update_touched(ctx.files())
    files.update_added(filesadded)
    files.update_removed(filesremoved)
    files.update_merged(filesmerged)
    files.update_copies_from_p1(filescopies[0])
    files.update_copies_from_p2(filescopies[1])
    return files


def _process_root(ctx):
    """compute the appropriate changed files for a changeset with no parents
    """

        if copy_info:
            source, srcnode = copy_info
            copied(source, filename)

    return md


def computechangesetfilesadded(ctx):
    """return the list of files added in a changeset
    """

45668:47ad23549b81

# coding: utf8
# metadata.py -- code related to various metadata computation and access.
#
# Copyright 2019 Google, Inc <[e-mail]>
# Copyright 2020 Pierre-Yves David <[e-mail]>
#

        # In the wild, one can encounter changeset where p1 is null but p2 is not
        return _process_linear(p1, ctx, parent=2)
    elif p1.rev() == p2.rev():
        # In the wild, one can encounter such "non-merge"
        return _process_linear(p1, ctx)
    else:
        return _process_merge(p1, p2, ctx)


def _process_root(ctx):
    """compute the appropriate changed files for a changeset with no parents
    """

        if copy_info:
            source, srcnode = copy_info
            copied(source, filename)

    return md


def _process_merge(p1_ctx, p2_ctx, ctx):
    """compute the appropriate changed files for a changeset with two parents

    This is a more advance case. The information we need to record is summarise
    in the following table:

    ┌──────────────┬──────────────┬──────────────┬──────────────┬──────────────┐
    │ diff ╲  diff │       ø      │ (Some, None) │ (None, Some) │ (Some, Some) │
    │  p2   ╲  p1  │              │              │              │              │
    ├──────────────┼──────────────┼──────────────┼──────────────┼──────────────┤
    │              │              │🄱  No Changes │🄳  No Changes │              │
    │  ø           │🄰  No Changes │      OR      │     OR       │🄵  No Changes │
    │              │              │🄲  Deleted[1] │🄴  Salvaged[2]│     [3]      │
    ├──────────────┼──────────────┼──────────────┼──────────────┼──────────────┤
    │              │🄶  No Changes │              │              │              │
    │ (Some, None) │      OR      │🄻  Deleted    │       ø      │      ø       │
    │              │🄷  Deleted[1] │              │              │              │
    ├──────────────┼──────────────┼──────────────┼──────────────┼──────────────┤
    │              │🄸  No Changes │              │              │              │
    │ (None, Some) │     OR       │      ø       │🄼   Added     │🄽   Merged    │
    │              │🄹  Salvaged[2]│              │   (copied?)  │   (copied?)  │
    ├──────────────┼──────────────┼──────────────┼──────────────┼──────────────┤
    │              │              │              │              │              │
    │ (Some, Some) │🄺  No Changes │      ø       │🄾   Merged    │🄿   Merged    │
    │              │     [3]      │              │   (copied?)  │   (copied?)  │
    └──────────────┴──────────────┴──────────────┴──────────────┴──────────────┘

    Special case [1]:

      The situation is:
        - parent-A:     file exists,
        - parent-B:     no file,
        - working-copy: no file.

      Detecting a "deletion" will depend on the presence of actual change on
      the "parent-A" branch:

      Subcase 🄱 or 🄶 : if the state of the file in "parent-A" is unchanged
      compared to the merge ancestors, then parent-A branch left the file
      untouched while parent-B deleted it. We simply apply the change from
      "parent-B" branch the file was automatically dropped.
      The result is:
          - file is not recorded as touched by the merge.

      Subcase 🄲 or 🄷 : otherwise, the change from parent-A branch were explicitly dropped and
      the file was "deleted again". From a user perspective, the message
      about "locally changed" while "remotely deleted" (or the other way
      around) was issued and the user chose to deleted the file.
      The result:
          - file is recorded as touched by the merge.


    Special case [2]:

      The situation is:
        - parent-A:     no file,
        - parent-B:     file,
        - working-copy: file (same content as parent-B).

      There are three subcases depending on the ancestors contents:

      - A) the file is missing in all ancestors,
      - B) at least one ancestor has the file with filenode ≠ from parent-B,
      - C) all ancestors use the same filenode as parent-B,

      Subcase (A) is the simpler, nothing happend on parent-A side while
      parent-B added it.

        The result:
            - the file is not marked as touched by the merge.

      Subcase (B) is the counter part of "Special case [1]", the file was
        modified on parent-B side, while parent-A side deleted it. However this
        time, the conflict was solved by keeping the file (and its
        modification). We consider the file as "salvaged".

        The result:
            - the file is marked as "salvaged" by the merge.

      Subcase (C) is subtle variation of the case above. In this case, the
        file in unchanged on the parent-B side and actively removed on the
        parent-A side. So the merge machinery correctly decide it should be
        removed. However, the file was explicitly restored to its parent-B
        content before the merge was commited. The file is be marked
        as salvaged too. From the merge result perspective, this is similar to
        Subcase (B), however from the merge resolution perspective they differ
        since in (C), there was some conflict not obvious solution to the
        merge (That got reversed)

    Special case [3]:

      The situation is:
        - parent-A:     file,
        - parent-B:     file (different filenode as parent-A),
        - working-copy: file (same filenode as parent-B).

      This case is in theory much simple, for this to happens, this mean the
      filenode in parent-A is purely replacing the one in parent-B (either a
      descendant, or a full new file history, see changeset). So the merge
      introduce no changes, and the file is not affected by the merge...

      However, in the wild it is possible to find commit with the above is not
      True. For example repository have some commit where the *new* node is an
      ancestor of the node in parent-A, or where parent-A and parent-B are two
      branches of the same file history, yet not merge-filenode were created
      (while the "merge" should have led to a "modification").

      Detecting such cases (and not recording the file as modified) would be a
      nice bonus. However do not any of this yet.
    """

    md = ChangingFiles()

    m = ctx.manifest()
    p1m = p1_ctx.manifest()
    p2m = p2_ctx.manifest()
    diff_p1 = p1m.diff(m)
    diff_p2 = p2m.diff(m)

    cahs = ctx.repo().changelog.commonancestorsheads(
        p1_ctx.node(), p2_ctx.node()
    )
    if not cahs:
        cahs = [node.nullrev]
    mas = [ctx.repo()[r].manifest() for r in cahs]

    copy_candidates = []

    # Dealing with case 🄰 happens automatically.  Since there are no entry in
    # d1 nor d2, we won't iterate on it ever.

    # Iteration over d1 content will deal with all cases, but the one in the
    # first column of the table.
    for filename, d1 in diff_p1.items():

        d2 = diff_p2.pop(filename, None)

        if d2 is None:
            # this deal with the first line of the table.
            _process_other_unchanged(md, mas, filename, d1)
        else:

            if d1[0][0] is None and d2[0][0] is None:
                # case 🄼 — both deleted the file.
                md.mark_added(filename)
                copy_candidates.append(filename)
            elif d1[1][0] is None and d2[1][0] is None:
                # case 🄻 — both deleted the file.
                md.mark_removed(filename)
            elif d1[1][0] is not None and d2[1][0] is not None:
                # case 🄽 🄾 🄿
                md.mark_merged(filename)
                copy_candidates.append(filename)
            else:
                # Impossible case, the post-merge file status cannot be None on
                # one side and Something on the other side.
                assert False, "unreachable"

    # Iteration over remaining d2 content deal with the first column of the
    # table.
    for filename, d2 in diff_p2.items():
        _process_other_unchanged(md, mas, filename, d2)

    for filename in copy_candidates:
        copy_info = ctx[filename].renamed()
        if copy_info:
            source, srcnode = copy_info
            if source in p1_ctx and p1_ctx[source].filenode() == srcnode:
                md.mark_copied_from_p1(source, filename)
            elif source in p2_ctx and p2_ctx[source].filenode() == srcnode:
                md.mark_copied_from_p2(source, filename)
    return md


def _find(manifest, filename):
    """return the associate filenode or None"""
    if filename not in manifest:
        return None
    return manifest.find(filename)[0]


def _process_other_unchanged(md, mas, filename, diff):
    source_node = diff[0][0]
    target_node = diff[1][0]

    if source_node is not None and target_node is None:
        if any(not _find(ma, filename) == source_node for ma in mas):
            # case 🄲 of 🄷
            md.mark_removed(filename)
        # else, we have case 🄱 or 🄶 : no change need to be recorded
    elif source_node is None and target_node is not None:
        if any(_find(ma, filename) is not None for ma in mas):
            # case 🄴 or 🄹
            md.mark_salvaged(filename)
        # else, we have case 🄳 or 🄸 : simple merge without intervention
    elif source_node is not None and target_node is not None:
        # case 🄵  or 🄺 : simple merge without intervention
        #
        # In buggy case where source_node is not an ancestors of target_node.
        # There should have a been a new filenode created, recording this as
        # "modified". We do not deal with them yet.
        pass
    else:
        # An impossible case, the diff algorithm should not return entry if the
        # file is missing on both side.
        assert False, "unreachable"


def _missing_from_all_ancestors(mas, filename):
    return all(_find(ma, filename) is None for ma in mas)


def computechangesetfilesadded(ctx):
    """return the list of files added in a changeset
    """