diff 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

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hgext/git/manifest.py	Tue Feb 11 00:44:59 2020 -0500
@@ -0,0 +1,293 @@
+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
+
+
[e-mail](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))
+
+
[e-mail](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]
+
+
[e-mail](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