hgext/fastannotate/support.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 2016-present Facebook. All Rights Reserved.
#
# support: fastannotate support for hgweb, and filectx
#
# 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

from mercurial.pycompat import getattr
from mercurial import (
    context as hgcontext,
    dagop,
    extensions,
    hgweb,
    patch,
    util,
)

from . import (
    context,
    revmap,
)


class _lazyfctx(object):
    """delegates to fctx but do not construct fctx when unnecessary"""

    def __init__(self, repo, node, path):
        self._node = node
        self._path = path
        self._repo = repo

    def node(self):
        return self._node

    def path(self):
        return self._path

    @util.propertycache
    def _fctx(self):
        return context.resolvefctx(self._repo, self._node, self._path)

    def __getattr__(self, name):
        return getattr(self._fctx, name)


def _convertoutputs(repo, annotated, contents):
    """convert fastannotate outputs to vanilla annotate format"""
    # fastannotate returns: [(nodeid, linenum, path)], [linecontent]
    # convert to what fctx.annotate returns: [annotateline]
    results = []
    fctxmap = {}
    annotateline = dagop.annotateline
    for i, (hsh, linenum, path) in enumerate(annotated):
        if (hsh, path) not in fctxmap:
            fctxmap[(hsh, path)] = _lazyfctx(repo, hsh, path)
        # linenum: the user wants 1-based, we have 0-based.
        lineno = linenum + 1
        fctx = fctxmap[(hsh, path)]
        line = contents[i]
        results.append(annotateline(fctx=fctx, lineno=lineno, text=line))
    return results


def _getmaster(fctx):
    """(fctx) -> str"""
    return fctx._repo.ui.config(b'fastannotate', b'mainbranch') or b'default'


def _doannotate(fctx, follow=True, diffopts=None):
    """like the vanilla fctx.annotate, but do it via fastannotate, and make
    the output format compatible with the vanilla fctx.annotate.
    may raise Exception, and always return line numbers.
    """
    master = _getmaster(fctx)

    with context.fctxannotatecontext(fctx, follow, diffopts) as ac:
        try:
            annotated, contents = ac.annotate(
                fctx.rev(), master=master, showpath=True, showlines=True
            )
        except Exception:
            ac.rebuild()  # try rebuild once
            fctx._repo.ui.debug(
                b'fastannotate: %s: rebuilding broken cache\n' % fctx._path
            )
            try:
                annotated, contents = ac.annotate(
                    fctx.rev(), master=master, showpath=True, showlines=True
                )
            except Exception:
                raise

    assert annotated and contents
    return _convertoutputs(fctx._repo, annotated, contents)


def _hgwebannotate(orig, fctx, ui):
    diffopts = patch.difffeatureopts(
        ui, untrusted=True, section=b'annotate', whitespace=True
    )
    return _doannotate(fctx, diffopts=diffopts)


def _fctxannotate(
    orig, self, follow=False, linenumber=False, skiprevs=None, diffopts=None
):
    if skiprevs:
        # skiprevs is not supported yet
        return orig(
            self, follow, linenumber, skiprevs=skiprevs, diffopts=diffopts
        )
    try:
        return _doannotate(self, follow, diffopts)
    except Exception as ex:
        self._repo.ui.debug(
            b'fastannotate: falling back to the vanilla annotate: %r\n' % ex
        )
        return orig(self, follow=follow, skiprevs=skiprevs, diffopts=diffopts)


def _remotefctxannotate(orig, self, follow=False, skiprevs=None, diffopts=None):
    # skipset: a set-like used to test if a fctx needs to be downloaded
    with context.fctxannotatecontext(self, follow, diffopts) as ac:
        skipset = revmap.revmap(ac.revmappath)
    return orig(
        self, follow, skiprevs=skiprevs, diffopts=diffopts, prefetchskip=skipset
    )


def replacehgwebannotate():
    extensions.wrapfunction(hgweb.webutil, b'annotate', _hgwebannotate)


def replacefctxannotate():
    extensions.wrapfunction(hgcontext.basefilectx, b'annotate', _fctxannotate)