annotate hgext/git/manifest.py @ 44477:ad718271a9eb

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

from __future__ import absolute_import

import pygit2

from mercurial import (
    match as matchmod,
    pathutil,
    pycompat,
    util,
)
from mercurial.interfaces import (
    repository,
    util as interfaceutil,
)
from . import gitutil


@interfaceutil.implementer(repository.imanifestdict)
class gittreemanifest(object):
    """Expose git trees (and optionally a builder's overlay) as a manifestdict.

    Very similar to mercurial.manifest.treemanifest.
    """

    def __init__(self, git_repo, root_tree, pending_changes):
        """Initializer.

        Args:
          git_repo: The git_repo we're walking (required to look up child
              trees).
          root_tree: The root Git tree object for this manifest.
          pending_changes: A dict in which pending changes will be
              tracked. The enclosing memgittreemanifestctx will use this to
              construct any required Tree objects in Git during it's
              `write()` method.
        """
        self._git_repo = git_repo
        self._tree = root_tree
        if pending_changes is None:
            pending_changes = {}
        # dict of path: Optional[Tuple(node, flags)]
        self._pending_changes = pending_changes

    def _resolve_entry(self, path):
        """Given a path, load its node and flags, or raise KeyError if missing.

        This takes into account any pending writes in the builder.
        """
        upath = pycompat.fsdecode(path)
        ent = None
        if path in self._pending_changes:
            val = self._pending_changes[path]
            if val is None:
                raise KeyError
            return val
        t = self._tree
        comps = upath.split('/')
        for comp in comps[:-1]:
            te = self._tree[comp]
            t = self._git_repo[te.id]
        ent = t[comps[-1]]
        if ent.filemode == pygit2.GIT_FILEMODE_BLOB:
            flags = b''
        elif ent.filemode == pygit2.GIT_FILEMODE_BLOB_EXECUTABLE:
            flags = b'x'
        elif ent.filemode == pygit2.GIT_FILEMODE_LINK:
            flags = b'l'
        else:
            raise ValueError('unsupported mode %s' % oct(ent.filemode))
        return ent.id.raw, flags

    def __getitem__(self, path):
        return self._resolve_entry(path)[0]

    def find(self, path):
        return self._resolve_entry(path)

    def __len__(self):
        return len(list(self.walk(matchmod.always())))

    def __nonzero__(self):
        try:
            next(iter(self))
            return True
        except StopIteration:
            return False

    __bool__ = __nonzero__

    def __contains__(self, path):
        try:
            self._resolve_entry(path)
            return True
        except KeyError:
            return False

    def iterkeys(self):
        return self.walk(matchmod.always())

    def keys(self):
        return list(self.iterkeys())

    def __iter__(self):
        return self.iterkeys()

    def __setitem__(self, path, node):
        self._pending_changes[path] = node, self.flags(path)

    def __delitem__(self, path):
        # TODO: should probably KeyError for already-deleted  files?
        self._pending_changes[path] = None

    def filesnotin(self, other, match=None):
        if match is not None:
            match = matchmod.badmatch(match, lambda path, msg: None)
            sm2 = set(other.walk(match))
            return {f for f in self.walk(match) if f not in sm2}
        return {f for f in self if f not in other}

    @util.propertycache
    def _dirs(self):
        return pathutil.dirs(self)

    def hasdir(self, dir):
        return dir in self._dirs

    def diff(self, other, match=None, clean=False):
        # TODO
        assert False

    def setflag(self, path, flag):
        node, unused_flag = self._resolve_entry(path)
        self._pending_changes[path] = node, flag

    def get(self, path, default=None):
        try:
            return self._resolve_entry(path)[0]
        except KeyError:
            return default

    def flags(self, path):
        try:
            return self._resolve_entry(path)[1]
        except KeyError:
            return b''

    def copy(self):
        pass

    def items(self):
        for f in self:
            # TODO: build a proper iterator version of this
            yield self[f]

    def iteritems(self):
        return self.items()

    def iterentries(self):
        for f in self:
            # TODO: build a proper iterator version of this
            yield self._resolve_entry(f)

    def text(self):
        assert False  # TODO can this method move out of the manifest iface?

    def _walkonetree(self, tree, match, subdir):
        for te in tree:
            # TODO: can we prune dir walks with the matcher?
            realname = subdir + pycompat.fsencode(te.name)
            if te.type == r'tree':
                for inner in self._walkonetree(
                    self._git_repo[te.id], match, realname + b'/'
                ):
                    yield inner
            if not match(realname):
                continue
            yield pycompat.fsencode(realname)

    def walk(self, match):
        # TODO: this is a very lazy way to merge in the pending
        # changes. There is absolutely room for optimization here by
        # being clever about walking over the sets...
        baseline = set(self._walkonetree(self._tree, match, b''))
        deleted = {p for p, v in self._pending_changes.items() if v is None}
        pend = {p for p in self._pending_changes if match(p)}
        return iter(sorted((baseline | pend) - deleted))


@interfaceutil.implementer(repository.imanifestrevisionstored)
class gittreemanifestctx(object):
    def __init__(self, repo, gittree):
        self._repo = repo
        self._tree = gittree

    def read(self):
        return gittreemanifest(self._repo, self._tree, None)

    def copy(self):
        # NB: it's important that we return a memgittreemanifestctx
        # because the caller expects a mutable manifest.
        return memgittreemanifestctx(self._repo, self._tree)

    def find(self, path):
        self.read()[path]


@interfaceutil.implementer(repository.imanifestrevisionwritable)
class memgittreemanifestctx(object):
    def __init__(self, repo, tree):
        self._repo = repo
        self._tree = tree
        # dict of path: Optional[Tuple(node, flags)]
        self._pending_changes = {}

    def read(self):
        return gittreemanifest(self._repo, self._tree, self._pending_changes)

    def copy(self):
        # TODO: if we have a builder in play, what should happen here?
        # Maybe we can shuffle copy() into the immutable interface.
        return memgittreemanifestctx(self._repo, self._tree)

    def write(self, transaction, link, p1, p2, added, removed, match=None):
        # We're not (for now, anyway) going to audit filenames, so we
        # can ignore added and removed.

        # TODO what does this match argument get used for? hopefully
        # just narrow?
        assert not match or isinstance(match, matchmod.alwaysmatcher)

        touched_dirs = pathutil.dirs(self._pending_changes)
        trees = {
            b'': self._tree,
        }
        # path: treebuilder
        builders = {
            b'': self._repo.TreeBuilder(self._tree),
        }
        # get a TreeBuilder for every tree in the touched_dirs set
        for d in sorted(touched_dirs, key=lambda x: (len(x), x)):
            if d == b'':
                # loaded root tree above
                continue
            comps = d.split(b'/')
            full = b''
            for part in comps:
                parent = trees[full]
                try:
                    new = self._repo[parent[pycompat.fsdecode(part)]]
                except KeyError:
                    # new directory
                    new = None
                full += b'/' + part
                if new is not None:
                    # existing directory
                    trees[full] = new
                    builders[full] = self._repo.TreeBuilder(new)
                else:
                    # new directory, use an empty dict to easily
                    # generate KeyError as any nested new dirs get
                    # created.
                    trees[full] = {}
                    builders[full] = self._repo.TreeBuilder()
        for f, info in self._pending_changes.items():
            if b'/' not in f:
                dirname = b''
                basename = f
            else:
                dirname, basename = f.rsplit(b'/', 1)
                dirname = b'/' + dirname
            if info is None:
                builders[dirname].remove(pycompat.fsdecode(basename))
            else:
                n, fl = info
                mode = {
                    b'': pygit2.GIT_FILEMODE_BLOB,
                    b'x': pygit2.GIT_FILEMODE_BLOB_EXECUTABLE,
                    b'l': pygit2.GIT_FILEMODE_LINK,
                }[fl]
                builders[dirname].insert(
                    pycompat.fsdecode(basename), gitutil.togitnode(n), mode
                )
        # This visits the buffered TreeBuilders in deepest-first
        # order, bubbling up the edits.
        for b in sorted(builders, key=len, reverse=True):
            if b == b'':
                break
            cb = builders[b]
            dn, bn = b.rsplit(b'/', 1)
            builders[dn].insert(
                pycompat.fsdecode(bn), cb.write(), pygit2.GIT_FILEMODE_TREE
            )
        return builders[b''].write().raw