view hgext/fastannotate/protocol.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

# Copyright 2016-present Facebook. All Rights Reserved.
#
# protocol: logic for a server providing fastannotate support
#
# 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

import contextlib
import os

from mercurial.i18n import _
from mercurial.pycompat import open
from mercurial import (
    error,
    extensions,
    hg,
    pycompat,
    util,
    wireprotov1peer,
    wireprotov1server,
)
from . import context

# common


def _getmaster(ui):
    """get the mainbranch, and enforce it is set"""
    master = ui.config(b'fastannotate', b'mainbranch')
    if not master:
        raise error.Abort(
            _(
                b'fastannotate.mainbranch is required '
                b'for both the client and the server'
            )
        )
    return master


# server-side


def _capabilities(orig, repo, proto):
    result = orig(repo, proto)
    result.append(b'getannotate')
    return result


def _getannotate(repo, proto, path, lastnode):
    # output:
    #   FILE := vfspath + '\0' + str(size) + '\0' + content
    #   OUTPUT := '' | FILE + OUTPUT
    result = b''
    buildondemand = repo.ui.configbool(
        b'fastannotate', b'serverbuildondemand', True
    )
    with context.annotatecontext(repo, path) as actx:
        if buildondemand:
            # update before responding to the client
            master = _getmaster(repo.ui)
            try:
                if not actx.isuptodate(master):
                    actx.annotate(master, master)
            except Exception:
                # non-fast-forward move or corrupted. rebuild automically.
                actx.rebuild()
                try:
                    actx.annotate(master, master)
                except Exception:
                    actx.rebuild()  # delete files
            finally:
                # although the "with" context will also do a close/flush, we
                # need to do it early so we can send the correct respond to
                # client.
                actx.close()
        # send back the full content of revmap and linelog, in the future we
        # may want to do some rsync-like fancy updating.
        # the lastnode check is not necessary if the client and the server
        # agree where the main branch is.
        if actx.lastnode != lastnode:
            for p in [actx.revmappath, actx.linelogpath]:
                if not os.path.exists(p):
                    continue
                with open(p, b'rb') as f:
                    content = f.read()
                vfsbaselen = len(repo.vfs.base + b'/')
                relpath = p[vfsbaselen:]
                result += b'%s\0%d\0%s' % (relpath, len(content), content)
    return result


def _registerwireprotocommand():
    if b'getannotate' in wireprotov1server.commands:
        return
    wireprotov1server.wireprotocommand(b'getannotate', b'path lastnode')(
        _getannotate
    )


def serveruisetup(ui):
    _registerwireprotocommand()
    extensions.wrapfunction(wireprotov1server, b'_capabilities', _capabilities)


# client-side


def _parseresponse(payload):
    result = {}
    i = 0
    l = len(payload) - 1
    state = 0  # 0: vfspath, 1: size
    vfspath = size = b''
    while i < l:
        ch = payload[i : i + 1]
        if ch == b'\0':
            if state == 1:
                result[vfspath] = payload[i + 1 : i + 1 + int(size)]
                i += int(size)
                state = 0
                vfspath = size = b''
            elif state == 0:
                state = 1
        else:
            if state == 1:
                size += ch
            elif state == 0:
                vfspath += ch
        i += 1
    return result


def peersetup(ui, peer):
    class fastannotatepeer(peer.__class__):
        @wireprotov1peer.batchable
        def getannotate(self, path, lastnode=None):
            if not self.capable(b'getannotate'):
                ui.warn(_(b'remote peer cannot provide annotate cache\n'))
                yield None, None
            else:
                args = {b'path': path, b'lastnode': lastnode or b''}
                f = wireprotov1peer.future()
                yield args, f
                yield _parseresponse(f.value)

    peer.__class__ = fastannotatepeer


@contextlib.contextmanager
def annotatepeer(repo):
    ui = repo.ui

    remotepath = ui.expandpath(
        ui.config(b'fastannotate', b'remotepath', b'default')
    )
    peer = hg.peer(ui, {}, remotepath)

    try:
        yield peer
    finally:
        peer.close()


def clientfetch(repo, paths, lastnodemap=None, peer=None):
    """download annotate cache from the server for paths"""
    if not paths:
        return

    if peer is None:
        with annotatepeer(repo) as peer:
            return clientfetch(repo, paths, lastnodemap, peer)

    if lastnodemap is None:
        lastnodemap = {}

    ui = repo.ui
    results = []
    with peer.commandexecutor() as batcher:
        ui.debug(b'fastannotate: requesting %d files\n' % len(paths))
        for p in paths:
            results.append(
                batcher.callcommand(
                    b'getannotate',
                    {b'path': p, b'lastnode': lastnodemap.get(p)},
                )
            )

        for result in results:
            r = result.result()
            # TODO: pconvert these paths on the server?
            r = {util.pconvert(p): v for p, v in pycompat.iteritems(r)}
            for path in sorted(r):
                # ignore malicious paths
                if not path.startswith(b'fastannotate/') or b'/../' in (
                    path + b'/'
                ):
                    ui.debug(
                        b'fastannotate: ignored malicious path %s\n' % path
                    )
                    continue
                content = r[path]
                if ui.debugflag:
                    ui.debug(
                        b'fastannotate: writing %d bytes to %s\n'
                        % (len(content), path)
                    )
                repo.vfs.makedirs(os.path.dirname(path))
                with repo.vfs(path, b'wb') as f:
                    f.write(content)


def _filterfetchpaths(repo, paths):
    """return a subset of paths whose history is long and need to fetch linelog
    from the server. works with remotefilelog and non-remotefilelog repos.
    """
    threshold = repo.ui.configint(b'fastannotate', b'clientfetchthreshold', 10)
    if threshold <= 0:
        return paths

    result = []
    for path in paths:
        try:
            if len(repo.file(path)) >= threshold:
                result.append(path)
        except Exception:  # file not found etc.
            result.append(path)

    return result


def localreposetup(ui, repo):
    class fastannotaterepo(repo.__class__):
        def prefetchfastannotate(self, paths, peer=None):
            master = _getmaster(self.ui)
            needupdatepaths = []
            lastnodemap = {}
            try:
                for path in _filterfetchpaths(self, paths):
                    with context.annotatecontext(self, path) as actx:
                        if not actx.isuptodate(master, strict=False):
                            needupdatepaths.append(path)
                            lastnodemap[path] = actx.lastnode
                if needupdatepaths:
                    clientfetch(self, needupdatepaths, lastnodemap, peer)
            except Exception as ex:
                # could be directory not writable or so, not fatal
                self.ui.debug(b'fastannotate: prefetch failed: %r\n' % ex)

    repo.__class__ = fastannotaterepo


def clientreposetup(ui, repo):
    _registerwireprotocommand()
    if repo.local():
        localreposetup(ui, repo)
    # TODO: this mutates global state, but only if at least one repo
    # has the extension enabled. This is probably bad for hgweb.
    if peersetup not in hg.wirepeersetupfuncs:
        hg.wirepeersetupfuncs.append(peersetup)