view mercurial/logcmdutil.py @ 48687:f8f2ecdde4b5

branchmap: skip obsolete revisions while computing heads

It's time to make this part of core Mercurial obsolescence-aware.

Not considering obsolete revisions when computing heads is clearly what
Mercurial should do. But there are a couple of small issues:

- Let's say tip of the repo is obsolete. There are two ways of finding tiprev
  for branchcache (both are in use): looking at input data for update() and
  looking at computed heads after update(). Previously, repo tip would be
  tiprev of the branchcache. With this patch, an obsolete revision can no
  longer be tiprev. And depending on what way we use for finding tiprev (input
  data vs computed heads) we'll get a different result. This is relevant when
  recomputing cache key from cache contents, and may lead to updating cache for
  obsolete revisions multiple times (not from scratch, because it still would
  be considered valid for a subset of revisions in the repo).

- If all commits on a branch are obsolete, the branchcache will include that
  branch, but the list of heads will be empty (that's why there's now `if not
  heads` when recomputing tiprev/tipnode from cache contents). Having an entry
  for every branch is currently required for notify extension (and
  test-notify.t to pass), because notify doesn't handle revsets in its
  subscription config very well and will throw an error if e.g. a branch
  doesn't exist.

- Cloning static HTTP repos may try to stat() a non-existent obsstore file. The
  issue is that we now care about obsolescence during clone, but statichttpvfs
  doesn't implement a stat method, so a regular vfs.stat() is used, and it
  assumes that file is local and calls os.stat().  During a clone, we're trying
  to stat() .hg/store/obsstore, but in static HTTP case we provide a literal
  URL to the obsstore file on the remote as if it were a local file path. On
  windows it actually results in a failure in test-static-http.t.

The first issue is going to be addressed in a series dedicated to making sure
branchcache is properly and timely written on disk (it wasn't perfect even
before this patch, but there aren't enough tests to demonstrate that). The
second issue will be addressed in a future patch for notify extension that will
make it not raise an exception if a branch doesn't exist. And the third one was
partially addressed in the previous patch in this series and will be properly
fixed in a future patch when this series is accepted.

filteredhash() grows a keyword argument to make sure that branchcache is also
invalidated when there are new obsolete revisions in its repo view. This way
the on-disk cache format is unchanged and compatible between versions (although
it will obviously be recomputed when switching versions before/after this patch
and the repo has obsolete revisions).

There's one test that uses plain `hg up` without arguments while updated to a
pruned commit. To make this test pass, simply return current working directory
parent. Later in this series this code will be replaced by what prune command
does: updating to the closest non-obsolete ancestor.

Test changes:

test-branch-change.t: update branch head and cache update message. The head of
default listed in hg heads is changed because revision 2 was rewritten as 7,
and 1 is the closest ancestor on the same branch, so it's the head of default
now.

The cache invalidation message appears now because of the cache hash change,
since we're now accounting for obsolete revisions. Here's some context:

"served.hidden" repo filter means everything is visible (no filtered
revisions), so before this series branch2-served.hidden file would not contain
any cache hash, only revnum and node. Now it also has a hash when there are
obsolete changesets in the repo. The command that the message appears for is
changing branch of 5 and 6, which are now obsolete, so the cache hash changes.

In general, when cache is simply out-of-date, it can be updated using the old
version as a base. But if cache hash differs, then the cache for that
particular repo filter is recomputed (at least with the current
implementation). This is what happens here.

test-obsmarker-template.t: the pull reports 2 heads changed, but after that the
repo correctly sees only 1. The new message could be better, but it's still an
improvement over the previous one where hg pull suggested merging with an
obsolete revision.

test-obsolete.t: we can see these revisions in hg log --hidden, but they
shouldn't be considered heads even with --hidden.

test-rebase-obsolete{,2}.t: there were new heads created previously after
making new orphan changesets, but they weren't detected. Now we are properly
detecting and reporting them.

test-rebase-obsolete4.t: there's only one head now because the other head is
pruned and was falsely reported before.

test-static-http.t: add obsstore to the list of requested files. This file
doesn't exist on the remotes, but clients want it anyway (they get 404). This
is fine, because there are other nonexistent files that clients request, like
.hg/bookmarks or .hg/cache/tags2-served.

Differential Revision: https://phab.mercurial-scm.org/D12097

# logcmdutil.py - utility for log-like commands
#
# Copyright 2005-2007 Olivia Mackall <[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

import itertools
import os
import posixpath

from .i18n import _
from .node import nullrev, wdirrev

from .thirdparty import attr

from . import (
    dagop,
    error,
    formatter,
    graphmod,
    match as matchmod,
    mdiff,
    merge,
    patch,
    pathutil,
    pycompat,
    revset,
    revsetlang,
    scmutil,
    smartset,
    templatekw,
    templater,
    util,
)
from .utils import (
    dateutil,
    stringutil,
)


if pycompat.TYPE_CHECKING:
    from typing import (
        Any,
        Callable,
        Dict,
        Optional,
        Sequence,
        Tuple,
    )

    for t in (Any, Callable, Dict, Optional, Tuple):
        assert t


def getlimit(opts):
    """get the log limit according to option -l/--limit"""
    limit = opts.get(b'limit')
    if limit:
        try:
            limit = int(limit)
        except ValueError:
            raise error.InputError(_(b'limit must be a positive integer'))
        if limit <= 0:
            raise error.InputError(_(b'limit must be positive'))
    else:
        limit = None
    return limit


def diff_parent(ctx):
    """get the context object to use as parent when diffing


    If diff.merge is enabled, an overlayworkingctx of the auto-merged parents will be returned.
    """
    repo = ctx.repo()
    if repo.ui.configbool(b"diff", b"merge") and ctx.p2().rev() != nullrev:
        # avoid cycle context -> subrepo -> cmdutil -> logcmdutil
        from . import context

        wctx = context.overlayworkingctx(repo)
        wctx.setbase(ctx.p1())
        with repo.ui.configoverride(
            {
                (
                    b"ui",
                    b"forcemerge",
                ): b"internal:merge3-lie-about-conflicts",
            },
            b"merge-diff",
        ):
            with repo.ui.silent():
                merge.merge(ctx.p2(), wc=wctx)
        return wctx
    else:
        return ctx.p1()


def diffordiffstat(
    ui,
    repo,
    diffopts,
    ctx1,
    ctx2,
    match,
    changes=None,
    stat=False,
    fp=None,
    graphwidth=0,
    prefix=b'',
    root=b'',
    listsubrepos=False,
    hunksfilterfn=None,
):
    '''show diff or diffstat.'''
    if root:
        relroot = pathutil.canonpath(repo.root, repo.getcwd(), root)
    else:
        relroot = b''
    copysourcematch = None

    def compose(f, g):
        return lambda x: f(g(x))

    def pathfn(f):
        return posixpath.join(prefix, f)

    if relroot != b'':
        # XXX relative roots currently don't work if the root is within a
        # subrepo
        uipathfn = scmutil.getuipathfn(repo, legacyrelativevalue=True)
        uirelroot = uipathfn(pathfn(relroot))
        relroot += b'/'
        for matchroot in match.files():
            if not matchroot.startswith(relroot):
                ui.warn(
                    _(b'warning: %s not inside relative root %s\n')
                    % (uipathfn(pathfn(matchroot)), uirelroot)
                )

        relrootmatch = scmutil.match(ctx2, pats=[relroot], default=b'path')
        match = matchmod.intersectmatchers(match, relrootmatch)
        copysourcematch = relrootmatch

        checkroot = repo.ui.configbool(
            b'devel', b'all-warnings'
        ) or repo.ui.configbool(b'devel', b'check-relroot')

        def relrootpathfn(f):
            if checkroot and not f.startswith(relroot):
                raise AssertionError(
                    b"file %s doesn't start with relroot %s" % (f, relroot)
                )
            return f[len(relroot) :]

        pathfn = compose(relrootpathfn, pathfn)

    if stat:
        diffopts = diffopts.copy(context=0, noprefix=False)
        width = 80
        if not ui.plain():
            width = ui.termwidth() - graphwidth
        # If an explicit --root was given, don't respect ui.relative-paths
        if not relroot:
            pathfn = compose(scmutil.getuipathfn(repo), pathfn)

    chunks = ctx2.diff(
        ctx1,
        match,
        changes,
        opts=diffopts,
        pathfn=pathfn,
        copysourcematch=copysourcematch,
        hunksfilterfn=hunksfilterfn,
    )

    if fp is not None or ui.canwritewithoutlabels():
        out = fp or ui
        if stat:
            chunks = [patch.diffstat(util.iterlines(chunks), width=width)]
        for chunk in util.filechunkiter(util.chunkbuffer(chunks)):
            out.write(chunk)
    else:
        if stat:
            chunks = patch.diffstatui(util.iterlines(chunks), width=width)
        else:
            chunks = patch.difflabel(
                lambda chunks, **kwargs: chunks, chunks, opts=diffopts
            )
        if ui.canbatchlabeledwrites():

            def gen():
                for chunk, label in chunks:
                    yield ui.label(chunk, label=label)

            for chunk in util.filechunkiter(util.chunkbuffer(gen())):
                ui.write(chunk)
        else:
            for chunk, label in chunks:
                ui.write(chunk, label=label)

    node2 = ctx2.node()
    for subpath, sub in scmutil.itersubrepos(ctx1, ctx2):
        tempnode2 = node2
        try:
            if node2 is not None:
                tempnode2 = ctx2.substate[subpath][1]
        except KeyError:
            # A subrepo that existed in node1 was deleted between node1 and
            # node2 (inclusive). Thus, ctx2's substate won't contain that
            # subpath. The best we can do is to ignore it.
            tempnode2 = None
        submatch = matchmod.subdirmatcher(subpath, match)
        subprefix = repo.wvfs.reljoin(prefix, subpath)
        if listsubrepos or match.exact(subpath) or any(submatch.files()):
            sub.diff(
                ui,
                diffopts,
                tempnode2,
                submatch,
                changes=changes,
                stat=stat,
                fp=fp,
                prefix=subprefix,
            )


class changesetdiffer(object):
    """Generate diff of changeset with pre-configured filtering functions"""

    def _makefilematcher(self, ctx):
        return scmutil.matchall(ctx.repo())

    def _makehunksfilter(self, ctx):
        return None

    def showdiff(self, ui, ctx, diffopts, graphwidth=0, stat=False):
        diffordiffstat(
            ui,
            ctx.repo(),
            diffopts,
            diff_parent(ctx),
            ctx,
            match=self._makefilematcher(ctx),
            stat=stat,
            graphwidth=graphwidth,
            hunksfilterfn=self._makehunksfilter(ctx),
        )


def changesetlabels(ctx):
    labels = [b'log.changeset', b'changeset.%s' % ctx.phasestr()]
    if ctx.obsolete():
        labels.append(b'changeset.obsolete')
    if ctx.isunstable():
        labels.append(b'changeset.unstable')
        for instability in ctx.instabilities():
            labels.append(b'instability.%s' % instability)
    return b' '.join(labels)


class changesetprinter(object):
    '''show changeset information when templating not requested.'''

    def __init__(self, ui, repo, differ=None, diffopts=None, buffered=False):
        self.ui = ui
        self.repo = repo
        self.buffered = buffered
        self._differ = differ or changesetdiffer()
        self._diffopts = patch.diffallopts(ui, diffopts)
        self._includestat = diffopts and diffopts.get(b'stat')
        self._includediff = diffopts and diffopts.get(b'patch')
        self.header = {}
        self.hunk = {}
        self.lastheader = None
        self.footer = None
        self._columns = templatekw.getlogcolumns()

    def flush(self, ctx):
        rev = ctx.rev()
        if rev in self.header:
            h = self.header[rev]
            if h != self.lastheader:
                self.lastheader = h
                self.ui.write(h)
            del self.header[rev]
        if rev in self.hunk:
            self.ui.write(self.hunk[rev])
            del self.hunk[rev]

    def close(self):
        if self.footer:
            self.ui.write(self.footer)

    def show(self, ctx, copies=None, **props):
        props = pycompat.byteskwargs(props)
        if self.buffered:
            self.ui.pushbuffer(labeled=True)
            self._show(ctx, copies, props)
            self.hunk[ctx.rev()] = self.ui.popbuffer()
        else:
            self._show(ctx, copies, props)

    def _show(self, ctx, copies, props):
        '''show a single changeset or file revision'''
        changenode = ctx.node()
        graphwidth = props.get(b'graphwidth', 0)

        if self.ui.quiet:
            self.ui.write(
                b"%s\n" % scmutil.formatchangeid(ctx), label=b'log.node'
            )
            return

        columns = self._columns
        self.ui.write(
            columns[b'changeset'] % scmutil.formatchangeid(ctx),
            label=changesetlabels(ctx),
        )

        # branches are shown first before any other names due to backwards
        # compatibility
        branch = ctx.branch()
        # don't show the default branch name
        if branch != b'default':
            self.ui.write(columns[b'branch'] % branch, label=b'log.branch')

        for nsname, ns in pycompat.iteritems(self.repo.names):
            # branches has special logic already handled above, so here we just
            # skip it
            if nsname == b'branches':
                continue
            # we will use the templatename as the color name since those two
            # should be the same
            for name in ns.names(self.repo, changenode):
                self.ui.write(ns.logfmt % name, label=b'log.%s' % ns.colorname)
        if self.ui.debugflag:
            self.ui.write(
                columns[b'phase'] % ctx.phasestr(), label=b'log.phase'
            )
        for pctx in scmutil.meaningfulparents(self.repo, ctx):
            label = b'log.parent changeset.%s' % pctx.phasestr()
            self.ui.write(
                columns[b'parent'] % scmutil.formatchangeid(pctx), label=label
            )

        if self.ui.debugflag:
            mnode = ctx.manifestnode()
            if mnode is None:
                mnode = self.repo.nodeconstants.wdirid
                mrev = wdirrev
            else:
                mrev = self.repo.manifestlog.rev(mnode)
            self.ui.write(
                columns[b'manifest']
                % scmutil.formatrevnode(self.ui, mrev, mnode),
                label=b'ui.debug log.manifest',
            )
        self.ui.write(columns[b'user'] % ctx.user(), label=b'log.user')
        self.ui.write(
            columns[b'date'] % dateutil.datestr(ctx.date()), label=b'log.date'
        )

        if ctx.isunstable():
            instabilities = ctx.instabilities()
            self.ui.write(
                columns[b'instability'] % b', '.join(instabilities),
                label=b'log.instability',
            )

        elif ctx.obsolete():
            self._showobsfate(ctx)

        self._exthook(ctx)

        if self.ui.debugflag:
            files = ctx.p1().status(ctx)
            for key, value in zip(
                [b'files', b'files+', b'files-'],
                [files.modified, files.added, files.removed],
            ):
                if value:
                    self.ui.write(
                        columns[key] % b" ".join(value),
                        label=b'ui.debug log.files',
                    )
        elif ctx.files() and self.ui.verbose:
            self.ui.write(
                columns[b'files'] % b" ".join(ctx.files()),
                label=b'ui.note log.files',
            )
        if copies and self.ui.verbose:
            copies = [b'%s (%s)' % c for c in copies]
            self.ui.write(
                columns[b'copies'] % b' '.join(copies),
                label=b'ui.note log.copies',
            )

        extra = ctx.extra()
        if extra and self.ui.debugflag:
            for key, value in sorted(extra.items()):
                self.ui.write(
                    columns[b'extra'] % (key, stringutil.escapestr(value)),
                    label=b'ui.debug log.extra',
                )

        description = ctx.description().strip()
        if description:
            if self.ui.verbose:
                self.ui.write(
                    _(b"description:\n"), label=b'ui.note log.description'
                )
                self.ui.write(description, label=b'ui.note log.description')
                self.ui.write(b"\n\n")
            else:
                self.ui.write(
                    columns[b'summary'] % description.splitlines()[0],
                    label=b'log.summary',
                )
        self.ui.write(b"\n")

        self._showpatch(ctx, graphwidth)

    def _showobsfate(self, ctx):
        # TODO: do not depend on templater
        tres = formatter.templateresources(self.repo.ui, self.repo)
        t = formatter.maketemplater(
            self.repo.ui,
            b'{join(obsfate, "\n")}',
            defaults=templatekw.keywords,
            resources=tres,
        )
        obsfate = t.renderdefault({b'ctx': ctx}).splitlines()

        if obsfate:
            for obsfateline in obsfate:
                self.ui.write(
                    self._columns[b'obsolete'] % obsfateline,
                    label=b'log.obsfate',
                )

    def _exthook(self, ctx):
        """empty method used by extension as a hook point"""

    def _showpatch(self, ctx, graphwidth=0):
        if self._includestat:
            self._differ.showdiff(
                self.ui, ctx, self._diffopts, graphwidth, stat=True
            )
        if self._includestat and self._includediff:
            self.ui.write(b"\n")
        if self._includediff:
            self._differ.showdiff(
                self.ui, ctx, self._diffopts, graphwidth, stat=False
            )
        if self._includestat or self._includediff:
            self.ui.write(b"\n")


class changesetformatter(changesetprinter):
    """Format changeset information by generic formatter"""

    def __init__(
        self, ui, repo, fm, differ=None, diffopts=None, buffered=False
    ):
        changesetprinter.__init__(self, ui, repo, differ, diffopts, buffered)
        self._diffopts = patch.difffeatureopts(ui, diffopts, git=True)
        self._fm = fm

    def close(self):
        self._fm.end()

    def _show(self, ctx, copies, props):
        '''show a single changeset or file revision'''
        fm = self._fm
        fm.startitem()
        fm.context(ctx=ctx)
        fm.data(rev=scmutil.intrev(ctx), node=fm.hexfunc(scmutil.binnode(ctx)))

        datahint = fm.datahint()
        if self.ui.quiet and not datahint:
            return

        fm.data(
            branch=ctx.branch(),
            phase=ctx.phasestr(),
            user=ctx.user(),
            date=fm.formatdate(ctx.date()),
            desc=ctx.description(),
            bookmarks=fm.formatlist(ctx.bookmarks(), name=b'bookmark'),
            tags=fm.formatlist(ctx.tags(), name=b'tag'),
            parents=fm.formatlist(
                [fm.hexfunc(c.node()) for c in ctx.parents()], name=b'node'
            ),
        )

        if self.ui.debugflag or b'manifest' in datahint:
            fm.data(
                manifest=fm.hexfunc(
                    ctx.manifestnode() or self.repo.nodeconstants.wdirid
                )
            )
        if self.ui.debugflag or b'extra' in datahint:
            fm.data(extra=fm.formatdict(ctx.extra()))

        if (
            self.ui.debugflag
            or b'modified' in datahint
            or b'added' in datahint
            or b'removed' in datahint
        ):
            files = ctx.p1().status(ctx)
            fm.data(
                modified=fm.formatlist(files.modified, name=b'file'),
                added=fm.formatlist(files.added, name=b'file'),
                removed=fm.formatlist(files.removed, name=b'file'),
            )

        verbose = not self.ui.debugflag and self.ui.verbose
        if verbose or b'files' in datahint:
            fm.data(files=fm.formatlist(ctx.files(), name=b'file'))
        if verbose and copies or b'copies' in datahint:
            fm.data(
                copies=fm.formatdict(copies or {}, key=b'name', value=b'source')
            )

        if self._includestat or b'diffstat' in datahint:
            self.ui.pushbuffer()
            self._differ.showdiff(self.ui, ctx, self._diffopts, stat=True)
            fm.data(diffstat=self.ui.popbuffer())
        if self._includediff or b'diff' in datahint:
            self.ui.pushbuffer()
            self._differ.showdiff(self.ui, ctx, self._diffopts, stat=False)
            fm.data(diff=self.ui.popbuffer())


class changesettemplater(changesetprinter):
    """format changeset information.

    Note: there are a variety of convenience functions to build a
    changesettemplater for common cases. See functions such as:
    maketemplater, changesetdisplayer, buildcommittemplate, or other
    functions that use changesest_templater.
    """

    # Arguments before "buffered" used to be positional. Consider not
    # adding/removing arguments before "buffered" to not break callers.
    def __init__(
        self, ui, repo, tmplspec, differ=None, diffopts=None, buffered=False
    ):
        changesetprinter.__init__(self, ui, repo, differ, diffopts, buffered)
        # tres is shared with _graphnodeformatter()
        self._tresources = tres = formatter.templateresources(ui, repo)
        self.t = formatter.loadtemplater(
            ui,
            tmplspec,
            defaults=templatekw.keywords,
            resources=tres,
            cache=templatekw.defaulttempl,
        )
        self._counter = itertools.count()

        self._tref = tmplspec.ref
        self._parts = {
            b'header': b'',
            b'footer': b'',
            tmplspec.ref: tmplspec.ref,
            b'docheader': b'',
            b'docfooter': b'',
            b'separator': b'',
        }
        if tmplspec.mapfile:
            # find correct templates for current mode, for backward
            # compatibility with 'log -v/-q/--debug' using a mapfile
            tmplmodes = [
                (True, b''),
                (self.ui.verbose, b'_verbose'),
                (self.ui.quiet, b'_quiet'),
                (self.ui.debugflag, b'_debug'),
            ]
            for mode, postfix in tmplmodes:
                for t in self._parts:
                    cur = t + postfix
                    if mode and cur in self.t:
                        self._parts[t] = cur
        else:
            partnames = [p for p in self._parts.keys() if p != tmplspec.ref]
            m = formatter.templatepartsmap(tmplspec, self.t, partnames)
            self._parts.update(m)

        if self._parts[b'docheader']:
            self.ui.write(self.t.render(self._parts[b'docheader'], {}))

    def close(self):
        if self._parts[b'docfooter']:
            if not self.footer:
                self.footer = b""
            self.footer += self.t.render(self._parts[b'docfooter'], {})
        return super(changesettemplater, self).close()

    def _show(self, ctx, copies, props):
        '''show a single changeset or file revision'''
        props = props.copy()
        props[b'ctx'] = ctx
        props[b'index'] = index = next(self._counter)
        props[b'revcache'] = {b'copies': copies}
        graphwidth = props.get(b'graphwidth', 0)

        # write separator, which wouldn't work well with the header part below
        # since there's inherently a conflict between header (across items) and
        # separator (per item)
        if self._parts[b'separator'] and index > 0:
            self.ui.write(self.t.render(self._parts[b'separator'], {}))

        # write header
        if self._parts[b'header']:
            h = self.t.render(self._parts[b'header'], props)
            if self.buffered:
                self.header[ctx.rev()] = h
            else:
                if self.lastheader != h:
                    self.lastheader = h
                    self.ui.write(h)

        # write changeset metadata, then patch if requested
        key = self._parts[self._tref]
        self.ui.write(self.t.render(key, props))
        self._exthook(ctx)
        self._showpatch(ctx, graphwidth)

        if self._parts[b'footer']:
            if not self.footer:
                self.footer = self.t.render(self._parts[b'footer'], props)


def templatespec(tmpl, mapfile):
    assert not (tmpl and mapfile)
    if mapfile:
        return formatter.mapfile_templatespec(b'changeset', mapfile)
    else:
        return formatter.literal_templatespec(tmpl)


def _lookuptemplate(ui, tmpl, style):
    """Find the template matching the given template spec or style

    See formatter.lookuptemplate() for details.
    """

    # ui settings
    if not tmpl and not style:  # template are stronger than style
        tmpl = ui.config(b'command-templates', b'log')
        if tmpl:
            return formatter.literal_templatespec(templater.unquotestring(tmpl))
        else:
            style = util.expandpath(ui.config(b'ui', b'style'))

    if not tmpl and style:
        mapfile = style
        fp = None
        if not os.path.split(mapfile)[0]:
            (mapname, fp) = templater.try_open_template(
                b'map-cmdline.' + mapfile
            ) or templater.try_open_template(mapfile)
            if mapname:
                mapfile = mapname
        return formatter.mapfile_templatespec(b'changeset', mapfile, fp)

    return formatter.lookuptemplate(ui, b'changeset', tmpl)


def maketemplater(ui, repo, tmpl, buffered=False):
    """Create a changesettemplater from a literal template 'tmpl'
    byte-string."""
    spec = formatter.literal_templatespec(tmpl)
    return changesettemplater(ui, repo, spec, buffered=buffered)


def changesetdisplayer(ui, repo, opts, differ=None, buffered=False):
    """show one changeset using template or regular display.

    Display format will be the first non-empty hit of:
    1. option 'template'
    2. option 'style'
    3. [command-templates] setting 'log'
    4. [ui] setting 'style'
    If all of these values are either the unset or the empty string,
    regular display via changesetprinter() is done.
    """
    postargs = (differ, opts, buffered)
    spec = _lookuptemplate(ui, opts.get(b'template'), opts.get(b'style'))

    # machine-readable formats have slightly different keyword set than
    # plain templates, which are handled by changesetformatter.
    # note that {b'pickle', b'debug'} can also be added to the list if needed.
    if spec.ref in {b'cbor', b'json'}:
        fm = ui.formatter(b'log', opts)
        return changesetformatter(ui, repo, fm, *postargs)

    if not spec.ref and not spec.tmpl and not spec.mapfile:
        return changesetprinter(ui, repo, *postargs)

    return changesettemplater(ui, repo, spec, *postargs)


@attr.s
class walkopts(object):
    """Options to configure a set of revisions and file matcher factory
    to scan revision/file history
    """

    # raw command-line parameters, which a matcher will be built from
    pats = attr.ib()
    opts = attr.ib()

    # a list of revset expressions to be traversed; if follow, it specifies
    # the start revisions
    revspec = attr.ib()

    # miscellaneous queries to filter revisions (see "hg help log" for details)
    bookmarks = attr.ib(default=attr.Factory(list))
    branches = attr.ib(default=attr.Factory(list))
    date = attr.ib(default=None)
    keywords = attr.ib(default=attr.Factory(list))
    no_merges = attr.ib(default=False)
    only_merges = attr.ib(default=False)
    prune_ancestors = attr.ib(default=attr.Factory(list))
    users = attr.ib(default=attr.Factory(list))

    # miscellaneous matcher arguments
    include_pats = attr.ib(default=attr.Factory(list))
    exclude_pats = attr.ib(default=attr.Factory(list))

    # 0: no follow, 1: follow first, 2: follow both parents
    follow = attr.ib(default=0)

    # do not attempt filelog-based traversal, which may be fast but cannot
    # include revisions where files were removed
    force_changelog_traversal = attr.ib(default=False)

    # filter revisions by file patterns, which should be disabled only if
    # you want to include revisions where files were unmodified
    filter_revisions_by_pats = attr.ib(default=True)

    # sort revisions prior to traversal: 'desc', 'topo', or None
    sort_revisions = attr.ib(default=None)

    # limit number of changes displayed; None means unlimited
    limit = attr.ib(default=None)


def parseopts(ui, pats, opts):
    # type: (Any, Sequence[bytes], Dict[bytes, Any]) -> walkopts
    """Parse log command options into walkopts

    The returned walkopts will be passed in to getrevs() or makewalker().
    """
    if opts.get(b'follow_first'):
        follow = 1
    elif opts.get(b'follow'):
        follow = 2
    else:
        follow = 0

    if opts.get(b'graph'):
        if ui.configbool(b'experimental', b'log.topo'):
            sort_revisions = b'topo'
        else:
            sort_revisions = b'desc'
    else:
        sort_revisions = None

    return walkopts(
        pats=pats,
        opts=opts,
        revspec=opts.get(b'rev', []),
        bookmarks=opts.get(b'bookmark', []),
        # branch and only_branch are really aliases and must be handled at
        # the same time
        branches=opts.get(b'branch', []) + opts.get(b'only_branch', []),
        date=opts.get(b'date'),
        keywords=opts.get(b'keyword', []),
        no_merges=bool(opts.get(b'no_merges')),
        only_merges=bool(opts.get(b'only_merges')),
        prune_ancestors=opts.get(b'prune', []),
        users=opts.get(b'user', []),
        include_pats=opts.get(b'include', []),
        exclude_pats=opts.get(b'exclude', []),
        follow=follow,
        force_changelog_traversal=bool(opts.get(b'removed')),
        sort_revisions=sort_revisions,
        limit=getlimit(opts),
    )


def _makematcher(repo, revs, wopts):
    """Build matcher and expanded patterns from log options

    If --follow, revs are the revisions to follow from.

    Returns (match, pats, slowpath) where
    - match: a matcher built from the given pats and -I/-X opts
    - pats: patterns used (globs are expanded on Windows)
    - slowpath: True if patterns aren't as simple as scanning filelogs
    """
    # pats/include/exclude are passed to match.match() directly in
    # _matchfiles() revset, but a log-like command should build its matcher
    # with scmutil.match(). The difference is input pats are globbed on
    # platforms without shell expansion (windows).
    wctx = repo[None]
    match, pats = scmutil.matchandpats(wctx, wopts.pats, wopts.opts)
    slowpath = match.anypats() or (
        not match.always() and wopts.force_changelog_traversal
    )
    if not slowpath:
        if wopts.follow and wopts.revspec:
            # There may be the case that a path doesn't exist in some (but
            # not all) of the specified start revisions, but let's consider
            # the path is valid. Missing files will be warned by the matcher.
            startctxs = [repo[r] for r in revs]
            for f in match.files():
                found = False
                for c in startctxs:
                    if f in c:
                        found = True
                    elif c.hasdir(f):
                        # If a directory exists in any of the start revisions,
                        # take the slow path.
                        found = slowpath = True
                if not found:
                    raise error.StateError(
                        _(
                            b'cannot follow file not in any of the specified '
                            b'revisions: "%s"'
                        )
                        % f
                    )
        elif wopts.follow:
            for f in match.files():
                if f not in wctx:
                    # If the file exists, it may be a directory, so let it
                    # take the slow path.
                    if os.path.exists(repo.wjoin(f)):
                        slowpath = True
                        continue
                    else:
                        raise error.StateError(
                            _(
                                b'cannot follow file not in parent '
                                b'revision: "%s"'
                            )
                            % f
                        )
                filelog = repo.file(f)
                if not filelog:
                    # A file exists in wdir but not in history, which means
                    # the file isn't committed yet.
                    raise error.StateError(
                        _(b'cannot follow nonexistent file: "%s"') % f
                    )
        else:
            for f in match.files():
                filelog = repo.file(f)
                if not filelog:
                    # A zero count may be a directory or deleted file, so
                    # try to find matching entries on the slow path.
                    slowpath = True

        # We decided to fall back to the slowpath because at least one
        # of the paths was not a file. Check to see if at least one of them
        # existed in history - in that case, we'll continue down the
        # slowpath; otherwise, we can turn off the slowpath
        if slowpath:
            for path in match.files():
                if not path or path in repo.store:
                    break
            else:
                slowpath = False

    return match, pats, slowpath


def _fileancestors(repo, revs, match, followfirst):
    fctxs = []
    for r in revs:
        ctx = repo[r]
        fctxs.extend(ctx[f].introfilectx() for f in ctx.walk(match))

    # When displaying a revision with --patch --follow FILE, we have
    # to know which file of the revision must be diffed. With
    # --follow, we want the names of the ancestors of FILE in the
    # revision, stored in "fcache". "fcache" is populated as a side effect
    # of the graph traversal.
    fcache = {}

    def filematcher(ctx):
        return scmutil.matchfiles(repo, fcache.get(scmutil.intrev(ctx), []))

    def revgen():
        for rev, cs in dagop.filectxancestors(fctxs, followfirst=followfirst):
            fcache[rev] = [c.path() for c in cs]
            yield rev

    return smartset.generatorset(revgen(), iterasc=False), filematcher


def _makenofollowfilematcher(repo, pats, opts):
    '''hook for extensions to override the filematcher for non-follow cases'''
    return None


def revsingle(repo, revspec, default=b'.', localalias=None):
    """Resolves user-provided revset(s) into a single revision.

    This just wraps the lower-level scmutil.revsingle() in order to raise an
    exception indicating user error.
    """
    try:
        return scmutil.revsingle(repo, revspec, default, localalias)
    except error.RepoLookupError as e:
        raise error.InputError(e.args[0], hint=e.hint)


def revpair(repo, revs):
    """Resolves user-provided revset(s) into two revisions.

    This just wraps the lower-level scmutil.revpair() in order to raise an
    exception indicating user error.
    """
    try:
        return scmutil.revpair(repo, revs)
    except error.RepoLookupError as e:
        raise error.InputError(e.args[0], hint=e.hint)


def revrange(repo, specs, localalias=None):
    """Resolves user-provided revset(s).

    This just wraps the lower-level scmutil.revrange() in order to raise an
    exception indicating user error.
    """
    try:
        return scmutil.revrange(repo, specs, localalias)
    except error.RepoLookupError as e:
        raise error.InputError(e.args[0], hint=e.hint)


_opt2logrevset = {
    b'no_merges': (b'not merge()', None),
    b'only_merges': (b'merge()', None),
    b'_matchfiles': (None, b'_matchfiles(%ps)'),
    b'date': (b'date(%s)', None),
    b'branch': (b'branch(%s)', b'%lr'),
    b'_patslog': (b'filelog(%s)', b'%lr'),
    b'keyword': (b'keyword(%s)', b'%lr'),
    b'prune': (b'ancestors(%s)', b'not %lr'),
    b'user': (b'user(%s)', b'%lr'),
}


def _makerevset(repo, wopts, slowpath):
    """Return a revset string built from log options and file patterns"""
    opts = {
        b'branch': [b'literal:' + repo.lookupbranch(b) for b in wopts.branches],
        b'date': wopts.date,
        b'keyword': wopts.keywords,
        b'no_merges': wopts.no_merges,
        b'only_merges': wopts.only_merges,
        b'prune': wopts.prune_ancestors,
        b'user': [b'literal:' + v for v in wopts.users],
    }

    if wopts.filter_revisions_by_pats and slowpath:
        # pats/include/exclude cannot be represented as separate
        # revset expressions as their filtering logic applies at file
        # level. For instance "-I a -X b" matches a revision touching
        # "a" and "b" while "file(a) and not file(b)" does
        # not. Besides, filesets are evaluated against the working
        # directory.
        matchargs = [b'r:', b'd:relpath']
        for p in wopts.pats:
            matchargs.append(b'p:' + p)
        for p in wopts.include_pats:
            matchargs.append(b'i:' + p)
        for p in wopts.exclude_pats:
            matchargs.append(b'x:' + p)
        opts[b'_matchfiles'] = matchargs
    elif wopts.filter_revisions_by_pats and not wopts.follow:
        opts[b'_patslog'] = list(wopts.pats)

    expr = []
    for op, val in sorted(pycompat.iteritems(opts)):
        if not val:
            continue
        revop, listop = _opt2logrevset[op]
        if revop and b'%' not in revop:
            expr.append(revop)
        elif not listop:
            expr.append(revsetlang.formatspec(revop, val))
        else:
            if revop:
                val = [revsetlang.formatspec(revop, v) for v in val]
            expr.append(revsetlang.formatspec(listop, val))

    if wopts.bookmarks:
        expr.append(
            revsetlang.formatspec(
                b'%lr',
                [scmutil.format_bookmark_revspec(v) for v in wopts.bookmarks],
            )
        )

    if expr:
        expr = b'(' + b' and '.join(expr) + b')'
    else:
        expr = None
    return expr


def _initialrevs(repo, wopts):
    """Return the initial set of revisions to be filtered or followed"""
    if wopts.revspec:
        revs = revrange(repo, wopts.revspec)
    elif wopts.follow and repo.dirstate.p1() == repo.nullid:
        revs = smartset.baseset()
    elif wopts.follow:
        revs = repo.revs(b'.')
    else:
        revs = smartset.spanset(repo)
        revs.reverse()
    return revs


def makewalker(repo, wopts):
    # type: (Any, walkopts) -> Tuple[smartset.abstractsmartset, Optional[Callable[[Any], matchmod.basematcher]]]
    """Build (revs, makefilematcher) to scan revision/file history

    - revs is the smartset to be traversed.
    - makefilematcher is a function to map ctx to a matcher for that revision
    """
    revs = _initialrevs(repo, wopts)
    if not revs:
        return smartset.baseset(), None
    # TODO: might want to merge slowpath with wopts.force_changelog_traversal
    match, pats, slowpath = _makematcher(repo, revs, wopts)
    wopts = attr.evolve(wopts, pats=pats)

    filematcher = None
    if wopts.follow:
        if slowpath or match.always():
            revs = dagop.revancestors(repo, revs, followfirst=wopts.follow == 1)
        else:
            assert not wopts.force_changelog_traversal
            revs, filematcher = _fileancestors(
                repo, revs, match, followfirst=wopts.follow == 1
            )
        revs.reverse()
    if filematcher is None:
        filematcher = _makenofollowfilematcher(repo, wopts.pats, wopts.opts)
    if filematcher is None:

        def filematcher(ctx):
            return match

    expr = _makerevset(repo, wopts, slowpath)
    if wopts.sort_revisions:
        assert wopts.sort_revisions in {b'topo', b'desc'}
        if wopts.sort_revisions == b'topo':
            if not revs.istopo():
                revs = dagop.toposort(revs, repo.changelog.parentrevs)
                # TODO: try to iterate the set lazily
                revs = revset.baseset(list(revs), istopo=True)
        elif not (revs.isdescending() or revs.istopo()):
            # User-specified revs might be unsorted
            revs.sort(reverse=True)
    if expr:
        matcher = revset.match(None, expr)
        revs = matcher(repo, revs)
    if wopts.limit is not None:
        revs = revs.slice(0, wopts.limit)

    return revs, filematcher


def getrevs(repo, wopts):
    # type: (Any, walkopts) -> Tuple[smartset.abstractsmartset, Optional[changesetdiffer]]
    """Return (revs, differ) where revs is a smartset

    differ is a changesetdiffer with pre-configured file matcher.
    """
    revs, filematcher = makewalker(repo, wopts)
    if not revs:
        return revs, None
    differ = changesetdiffer()
    differ._makefilematcher = filematcher
    return revs, differ


def _parselinerangeopt(repo, opts):
    """Parse --line-range log option and return a list of tuples (filename,
    (fromline, toline)).
    """
    linerangebyfname = []
    for pat in opts.get(b'line_range', []):
        try:
            pat, linerange = pat.rsplit(b',', 1)
        except ValueError:
            raise error.InputError(
                _(b'malformatted line-range pattern %s') % pat
            )
        try:
            fromline, toline = map(int, linerange.split(b':'))
        except ValueError:
            raise error.InputError(_(b"invalid line range for %s") % pat)
        msg = _(b"line range pattern '%s' must match exactly one file") % pat
        fname = scmutil.parsefollowlinespattern(repo, None, pat, msg)
        linerangebyfname.append(
            (fname, util.processlinerange(fromline, toline))
        )
    return linerangebyfname


def getlinerangerevs(repo, userrevs, opts):
    """Return (revs, differ).

    "revs" are revisions obtained by processing "line-range" log options and
    walking block ancestors of each specified file/line-range.

    "differ" is a changesetdiffer with pre-configured file matcher and hunks
    filter.
    """
    wctx = repo[None]

    # Two-levels map of "rev -> file ctx -> [line range]".
    linerangesbyrev = {}
    for fname, (fromline, toline) in _parselinerangeopt(repo, opts):
        if fname not in wctx:
            raise error.StateError(
                _(b'cannot follow file not in parent revision: "%s"') % fname
            )
        fctx = wctx.filectx(fname)
        for fctx, linerange in dagop.blockancestors(fctx, fromline, toline):
            rev = fctx.introrev()
            if rev is None:
                rev = wdirrev
            if rev not in userrevs:
                continue
            linerangesbyrev.setdefault(rev, {}).setdefault(
                fctx.path(), []
            ).append(linerange)

    def nofilterhunksfn(fctx, hunks):
        return hunks

    def hunksfilter(ctx):
        fctxlineranges = linerangesbyrev.get(scmutil.intrev(ctx))
        if fctxlineranges is None:
            return nofilterhunksfn

        def filterfn(fctx, hunks):
            lineranges = fctxlineranges.get(fctx.path())
            if lineranges is not None:
                for hr, lines in hunks:
                    if hr is None:  # binary
                        yield hr, lines
                        continue
                    if any(mdiff.hunkinrange(hr[2:], lr) for lr in lineranges):
                        yield hr, lines
            else:
                for hunk in hunks:
                    yield hunk

        return filterfn

    def filematcher(ctx):
        files = list(linerangesbyrev.get(scmutil.intrev(ctx), []))
        return scmutil.matchfiles(repo, files)

    revs = sorted(linerangesbyrev, reverse=True)

    differ = changesetdiffer()
    differ._makefilematcher = filematcher
    differ._makehunksfilter = hunksfilter
    return smartset.baseset(revs), differ


def _graphnodeformatter(ui, displayer):
    spec = ui.config(b'command-templates', b'graphnode')
    if not spec:
        return templatekw.getgraphnode  # fast path for "{graphnode}"

    spec = templater.unquotestring(spec)
    if isinstance(displayer, changesettemplater):
        # reuse cache of slow templates
        tres = displayer._tresources
    else:
        tres = formatter.templateresources(ui)
    templ = formatter.maketemplater(
        ui, spec, defaults=templatekw.keywords, resources=tres
    )

    def formatnode(repo, ctx, cache):
        props = {b'ctx': ctx, b'repo': repo}
        return templ.renderdefault(props)

    return formatnode


def displaygraph(ui, repo, dag, displayer, edgefn, getcopies=None, props=None):
    props = props or {}
    formatnode = _graphnodeformatter(ui, displayer)
    state = graphmod.asciistate()
    styles = state.styles

    # only set graph styling if HGPLAIN is not set.
    if ui.plain(b'graph'):
        # set all edge styles to |, the default pre-3.8 behaviour
        styles.update(dict.fromkeys(styles, b'|'))
    else:
        edgetypes = {
            b'parent': graphmod.PARENT,
            b'grandparent': graphmod.GRANDPARENT,
            b'missing': graphmod.MISSINGPARENT,
        }
        for name, key in edgetypes.items():
            # experimental config: experimental.graphstyle.*
            styles[key] = ui.config(
                b'experimental', b'graphstyle.%s' % name, styles[key]
            )
            if not styles[key]:
                styles[key] = None

        # experimental config: experimental.graphshorten
        state.graphshorten = ui.configbool(b'experimental', b'graphshorten')

    formatnode_cache = {}
    for rev, type, ctx, parents in dag:
        char = formatnode(repo, ctx, formatnode_cache)
        copies = getcopies(ctx) if getcopies else None
        edges = edgefn(type, char, state, rev, parents)
        firstedge = next(edges)
        width = firstedge[2]
        displayer.show(
            ctx, copies=copies, graphwidth=width, **pycompat.strkwargs(props)
        )
        lines = displayer.hunk.pop(rev).split(b'\n')
        if not lines[-1]:
            del lines[-1]
        displayer.flush(ctx)
        for type, char, width, coldata in itertools.chain([firstedge], edges):
            graphmod.ascii(ui, state, type, char, lines, coldata)
            lines = []
    displayer.close()


def displaygraphrevs(ui, repo, revs, displayer, getrenamed):
    revdag = graphmod.dagwalker(repo, revs)
    displaygraph(ui, repo, revdag, displayer, graphmod.asciiedges, getrenamed)


def displayrevs(ui, repo, revs, displayer, getcopies):
    for rev in revs:
        ctx = repo[rev]
        copies = getcopies(ctx) if getcopies else None
        displayer.show(ctx, copies=copies)
        displayer.flush(ctx)
    displayer.close()


def checkunsupportedgraphflags(pats, opts):
    for op in [b"newest_first"]:
        if op in opts and opts[op]:
            raise error.InputError(
                _(b"-G/--graph option is incompatible with --%s")
                % op.replace(b"_", b"-")
            )


def graphrevs(repo, nodes, opts):
    limit = getlimit(opts)
    nodes.reverse()
    if limit is not None:
        nodes = nodes[:limit]
    return graphmod.nodes(repo, nodes)