hgext/convert/filemap.py

git: skeleton of a new extension to _directly_ operate on git repos

This is based in part of work I did years ago in hgit, but it's mostly
new code since I'm using pygit2 instead of dulwich and the hg storage
interfaces have improved. Some cleanup of old hgit code by Pulkit,
which I greatly appreciate.

test-git-interop.t does not cover a whole lot of cases, but it
passes. It includes status, diff, making a new commit, and `hg annotate`
working on the git repository.

This is _not_ (yet) production quality code: this is an
experiment. Known technical debt lurking in this implementation:

 * Writing bookmarks just totally ignores transactions.
 * The way progress is threaded down into the gitstore is awful.
 * Ideally we'd find a way to incrementally reindex DAGs. I'm not sure
   how to do that efficiently, so we might need a "known only fast-forwards"
   mode on the DAG indexer for use on `hg commit` and friends.
 * We don't even _try_ to do anything reasonable for `hg pull` or `hg push`.
 * Mercurial need an interface for the changelog type.

Tests currently require git 2.24 as far as I'm aware: `git status` has
some changed output that I didn't try and handle in a compatible way.

This patch has produced some interesting cleanups, most recently on
the manifest type. I expect continuing down this road will produce
other meritorious cleanups throughout our code.

Differential Revision: https://phab.mercurial-scm.org/D6734

# Copyright 2007 Bryan O'Sullivan <[e-mail]>
# Copyright 2007 Alexis S. L. Carvalho <[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.

from __future__ import absolute_import, print_function

import posixpath

from mercurial.i18n import _
from mercurial import (
    error,
    pycompat,
)
from . import common

SKIPREV = common.SKIPREV


def rpairs(path):
    '''Yield tuples with path split at '/', starting with the full path.
    No leading, trailing or double '/', please.
    >>> for x in rpairs(b'foo/bar/baz'): print(x)
    ('foo/bar/baz', '')
    ('foo/bar', 'baz')
    ('foo', 'bar/baz')
    ('.', 'foo/bar/baz')
    '''
    i = len(path)
    while i != -1:
        yield path[:i], path[i + 1 :]
        i = path.rfind(b'/', 0, i)
    yield b'.', path


def normalize(path):
    ''' We use posixpath.normpath to support cross-platform path format.
    However, it doesn't handle None input. So we wrap it up. '''
    if path is None:
        return None
    return posixpath.normpath(path)


class filemapper(object):
    '''Map and filter filenames when importing.
    A name can be mapped to itself, a new name, or None (omit from new
    repository).'''

    def __init__(self, ui, path=None):
        self.ui = ui
        self.include = {}
        self.exclude = {}
        self.rename = {}
        self.targetprefixes = None
        if path:
            if self.parse(path):
                raise error.Abort(_(b'errors in filemap'))

    def parse(self, path):
        errs = 0

        def check(name, mapping, listname):
            if not name:
                self.ui.warn(
                    _(b'%s:%d: path to %s is missing\n')
                    % (lex.infile, lex.lineno, listname)
                )
                return 1
            if name in mapping:
                self.ui.warn(
                    _(b'%s:%d: %r already in %s list\n')
                    % (lex.infile, lex.lineno, name, listname)
                )
                return 1
            if name.startswith(b'/') or name.endswith(b'/') or b'//' in name:
                self.ui.warn(
                    _(b'%s:%d: superfluous / in %s %r\n')
                    % (lex.infile, lex.lineno, listname, pycompat.bytestr(name))
                )
                return 1
            return 0

        lex = common.shlexer(
            filepath=path, wordchars=b'!@#$%^&*()-=+[]{}|;:,./<>?'
        )
        cmd = lex.get_token()
        while cmd:
            if cmd == b'include':
                name = normalize(lex.get_token())
                errs += check(name, self.exclude, b'exclude')
                self.include[name] = name
            elif cmd == b'exclude':
                name = normalize(lex.get_token())
                errs += check(name, self.include, b'include')
                errs += check(name, self.rename, b'rename')
                self.exclude[name] = name
            elif cmd == b'rename':
                src = normalize(lex.get_token())
                dest = normalize(lex.get_token())
                errs += check(src, self.exclude, b'exclude')
                self.rename[src] = dest
            elif cmd == b'source':
                errs += self.parse(normalize(lex.get_token()))
            else:
                self.ui.warn(
                    _(b'%s:%d: unknown directive %r\n')
                    % (lex.infile, lex.lineno, pycompat.bytestr(cmd))
                )
                errs += 1
            cmd = lex.get_token()
        return errs

    def lookup(self, name, mapping):
        name = normalize(name)
        for pre, suf in rpairs(name):
            try:
                return mapping[pre], pre, suf
            except KeyError:
                pass
        return b'', name, b''

    def istargetfile(self, filename):
        """Return true if the given target filename is covered as a destination
        of the filemap. This is useful for identifying what parts of the target
        repo belong to the source repo and what parts don't."""
        if self.targetprefixes is None:
            self.targetprefixes = set()
            for before, after in pycompat.iteritems(self.rename):
                self.targetprefixes.add(after)

        # If "." is a target, then all target files are considered from the
        # source.
        if not self.targetprefixes or b'.' in self.targetprefixes:
            return True

        filename = normalize(filename)
        for pre, suf in rpairs(filename):
            # This check is imperfect since it doesn't account for the
            # include/exclude list, but it should work in filemaps that don't
            # apply include/exclude to the same source directories they are
            # renaming.
            if pre in self.targetprefixes:
                return True
        return False

    def __call__(self, name):
        if self.include:
            inc = self.lookup(name, self.include)[0]
        else:
            inc = name
        if self.exclude:
            exc = self.lookup(name, self.exclude)[0]
        else:
            exc = b''
        if (not self.include and exc) or (len(inc) <= len(exc)):
            return None
        newpre, pre, suf = self.lookup(name, self.rename)
        if newpre:
            if newpre == b'.':
                return suf
            if suf:
                if newpre.endswith(b'/'):
                    return newpre + suf
                return newpre + b'/' + suf
            return newpre
        return name

    def active(self):
        return bool(self.include or self.exclude or self.rename)


# This class does two additional things compared to a regular source:
#
# - Filter and rename files.  This is mostly wrapped by the filemapper
#   class above. We hide the original filename in the revision that is
#   returned by getchanges to be able to find things later in getfile.
#
# - Return only revisions that matter for the files we're interested in.
#   This involves rewriting the parents of the original revision to
#   create a graph that is restricted to those revisions.
#
#   This set of revisions includes not only revisions that directly
#   touch files we're interested in, but also merges that merge two
#   or more interesting revisions.


class filemap_source(common.converter_source):
    def __init__(self, ui, baseconverter, filemap):
        super(filemap_source, self).__init__(ui, baseconverter.repotype)
        self.base = baseconverter
        self.filemapper = filemapper(ui, filemap)
        self.commits = {}
        # if a revision rev has parent p in the original revision graph, then
        # rev will have parent self.parentmap[p] in the restricted graph.
        self.parentmap = {}
        # self.wantedancestors[rev] is the set of all ancestors of rev that
        # are in the restricted graph.
        self.wantedancestors = {}
        self.convertedorder = None
        self._rebuilt = False
        self.origparents = {}
        self.children = {}
        self.seenchildren = {}
        # experimental config: convert.ignoreancestorcheck
        self.ignoreancestorcheck = self.ui.configbool(
            b'convert', b'ignoreancestorcheck'
        )

    def before(self):
        self.base.before()

    def after(self):
        self.base.after()

    def setrevmap(self, revmap):
        # rebuild our state to make things restartable
        #
        # To avoid calling getcommit for every revision that has already
        # been converted, we rebuild only the parentmap, delaying the
        # rebuild of wantedancestors until we need it (i.e. until a
        # merge).
        #
        # We assume the order argument lists the revisions in
        # topological order, so that we can infer which revisions were
        # wanted by previous runs.
        self._rebuilt = not revmap
        seen = {SKIPREV: SKIPREV}
        dummyset = set()
        converted = []
        for rev in revmap.order:
            mapped = revmap[rev]
            wanted = mapped not in seen
            if wanted:
                seen[mapped] = rev
                self.parentmap[rev] = rev
            else:
                self.parentmap[rev] = seen[mapped]
            self.wantedancestors[rev] = dummyset
            arg = seen[mapped]
            if arg == SKIPREV:
                arg = None
            converted.append((rev, wanted, arg))
        self.convertedorder = converted
        return self.base.setrevmap(revmap)

    def rebuild(self):
        if self._rebuilt:
            return True
        self._rebuilt = True
        self.parentmap.clear()
        self.wantedancestors.clear()
        self.seenchildren.clear()
        for rev, wanted, arg in self.convertedorder:
            if rev not in self.origparents:
                try:
                    self.origparents[rev] = self.getcommit(rev).parents
                except error.RepoLookupError:
                    self.ui.debug(b"unknown revmap source: %s\n" % rev)
                    continue
            if arg is not None:
                self.children[arg] = self.children.get(arg, 0) + 1

        for rev, wanted, arg in self.convertedorder:
            try:
                parents = self.origparents[rev]
            except KeyError:
                continue  # unknown revmap source
            if wanted:
                self.mark_wanted(rev, parents)
            else:
                self.mark_not_wanted(rev, arg)
            self._discard(arg, *parents)

        return True

    def getheads(self):
        return self.base.getheads()

    def getcommit(self, rev):
        # We want to save a reference to the commit objects to be able
        # to rewrite their parents later on.
        c = self.commits[rev] = self.base.getcommit(rev)
        for p in c.parents:
            self.children[p] = self.children.get(p, 0) + 1
        return c

    def numcommits(self):
        return self.base.numcommits()

    def _cachedcommit(self, rev):
        if rev in self.commits:
            return self.commits[rev]
        return self.base.getcommit(rev)

    def _discard(self, *revs):
        for r in revs:
            if r is None:
                continue
            self.seenchildren[r] = self.seenchildren.get(r, 0) + 1
            if self.seenchildren[r] == self.children[r]:
                self.wantedancestors.pop(r, None)
                self.parentmap.pop(r, None)
                del self.seenchildren[r]
                if self._rebuilt:
                    del self.children[r]

    def wanted(self, rev, i):
        # Return True if we're directly interested in rev.
        #
        # i is an index selecting one of the parents of rev (if rev
        # has no parents, i is None).  getchangedfiles will give us
        # the list of files that are different in rev and in the parent
        # indicated by i.  If we're interested in any of these files,
        # we're interested in rev.
        try:
            files = self.base.getchangedfiles(rev, i)
        except NotImplementedError:
            raise error.Abort(_(b"source repository doesn't support --filemap"))
        for f in files:
            if self.filemapper(f):
                return True

        # The include directive is documented to include nothing else (though
        # valid branch closes are included).
        if self.filemapper.include:
            return False

        # Allow empty commits in the source revision through.  The getchanges()
        # method doesn't even bother calling this if it determines that the
        # close marker is significant (i.e. all of the branch ancestors weren't
        # eliminated).  Therefore if there *is* a close marker, getchanges()
        # doesn't consider it significant, and this revision should be dropped.
        return not files and b'close' not in self.commits[rev].extra

    def mark_not_wanted(self, rev, p):
        # Mark rev as not interesting and update data structures.

        if p is None:
            # A root revision. Use SKIPREV to indicate that it doesn't
            # map to any revision in the restricted graph.  Put SKIPREV
            # in the set of wanted ancestors to simplify code elsewhere
            self.parentmap[rev] = SKIPREV
            self.wantedancestors[rev] = {SKIPREV}
            return

        # Reuse the data from our parent.
        self.parentmap[rev] = self.parentmap[p]
        self.wantedancestors[rev] = self.wantedancestors[p]

    def mark_wanted(self, rev, parents):
        # Mark rev ss wanted and update data structures.

        # rev will be in the restricted graph, so children of rev in
        # the original graph should still have rev as a parent in the
        # restricted graph.
        self.parentmap[rev] = rev

        # The set of wanted ancestors of rev is the union of the sets
        # of wanted ancestors of its parents. Plus rev itself.
        wrev = set()
        for p in parents:
            if p in self.wantedancestors:
                wrev.update(self.wantedancestors[p])
            else:
                self.ui.warn(
                    _(b'warning: %s parent %s is missing\n') % (rev, p)
                )
        wrev.add(rev)
        self.wantedancestors[rev] = wrev

    def getchanges(self, rev, full):
        parents = self.commits[rev].parents
        if len(parents) > 1 and not self.ignoreancestorcheck:
            self.rebuild()

        # To decide whether we're interested in rev we:
        #
        # - calculate what parents rev will have if it turns out we're
        #   interested in it.  If it's going to have more than 1 parent,
        #   we're interested in it.
        #
        # - otherwise, we'll compare it with the single parent we found.
        #   If any of the files we're interested in is different in the
        #   the two revisions, we're interested in rev.

        # A parent p is interesting if its mapped version (self.parentmap[p]):
        # - is not SKIPREV
        # - is still not in the list of parents (we don't want duplicates)
        # - is not an ancestor of the mapped versions of the other parents or
        #   there is no parent in the same branch than the current revision.
        mparents = []
        knownparents = set()
        branch = self.commits[rev].branch
        hasbranchparent = False
        for i, p1 in enumerate(parents):
            mp1 = self.parentmap[p1]
            if mp1 == SKIPREV or mp1 in knownparents:
                continue

            isancestor = not self.ignoreancestorcheck and any(
                p2
                for p2 in parents
                if p1 != p2
                and mp1 != self.parentmap[p2]
                and mp1 in self.wantedancestors[p2]
            )
            if not isancestor and not hasbranchparent and len(parents) > 1:
                # This could be expensive, avoid unnecessary calls.
                if self._cachedcommit(p1).branch == branch:
                    hasbranchparent = True
            mparents.append((p1, mp1, i, isancestor))
            knownparents.add(mp1)
        # Discard parents ancestors of other parents if there is a
        # non-ancestor one on the same branch than current revision.
        if hasbranchparent:
            mparents = [p for p in mparents if not p[3]]
        wp = None
        if mparents:
            wp = max(p[2] for p in mparents)
            mparents = [p[1] for p in mparents]
        elif parents:
            wp = 0

        self.origparents[rev] = parents

        closed = False
        if b'close' in self.commits[rev].extra:
            # A branch closing revision is only useful if one of its
            # parents belong to the branch being closed
            pbranches = [self._cachedcommit(p).branch for p in mparents]
            if branch in pbranches:
                closed = True

        if len(mparents) < 2 and not closed and not self.wanted(rev, wp):
            # We don't want this revision.
            # Update our state and tell the convert process to map this
            # revision to the same revision its parent as mapped to.
            p = None
            if parents:
                p = parents[wp]
            self.mark_not_wanted(rev, p)
            self.convertedorder.append((rev, False, p))
            self._discard(*parents)
            return self.parentmap[rev]

        # We want this revision.
        # Rewrite the parents of the commit object
        self.commits[rev].parents = mparents
        self.mark_wanted(rev, parents)
        self.convertedorder.append((rev, True, None))
        self._discard(*parents)

        # Get the real changes and do the filtering/mapping. To be
        # able to get the files later on in getfile, we hide the
        # original filename in the rev part of the return value.
        changes, copies, cleanp2 = self.base.getchanges(rev, full)
        files = {}
        ncleanp2 = set(cleanp2)
        for f, r in changes:
            newf = self.filemapper(f)
            if newf and (newf != f or newf not in files):
                files[newf] = (f, r)
                if newf != f:
                    ncleanp2.discard(f)
        files = sorted(files.items())

        ncopies = {}
        for c in copies:
            newc = self.filemapper(c)
            if newc:
                newsource = self.filemapper(copies[c])
                if newsource:
                    ncopies[newc] = newsource

        return files, ncopies, ncleanp2

    def targetfilebelongstosource(self, targetfilename):
        return self.filemapper.istargetfile(targetfilename)

    def getfile(self, name, rev):
        realname, realrev = rev
        return self.base.getfile(realname, realrev)

    def gettags(self):
        return self.base.gettags()

    def hasnativeorder(self):
        return self.base.hasnativeorder()

    def lookuprev(self, rev):
        return self.base.lookuprev(rev)

    def getbookmarks(self):
        return self.base.getbookmarks()

    def converted(self, rev, sinkrev):
        self.base.converted(rev, sinkrev)