hgext/largefiles/storefactory.py

branchcache: stop writing more branchcache file on disk than needed

Before this change, we were unconditionally writing a branchmap file for the
filter level passed to `update_disk`. This is actually counter productive if no
update were needed for this filter level. In many case, the branch cache for a
filter level is identical to its parent "subset" and it is better to simply
keep the subset update and reuse it every time instead of having to do identical
work for similar subset.

So we change the `update_disk` method to only write a file when that filter
level differ from its parent. This removes many cases where identical files were
written, requiring multiple boring update in the test suite.

The only notable changes is the change to `test-strip-branch-cache.t`, this
case was checking a scenario that no longer reproduce the bug as writing less
branchmap file result in less stalled cache on disk.

Strictly speaking, we could create a more convoluted scenario that create a
similar issue. However the next changeset would also cover that scenario so we
directly updated that test case to a "no longer buggy" state.

# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.


import re

from mercurial.i18n import _
from mercurial import (
    error,
    hg,
    util,
)
from mercurial.utils import (
    urlutil,
)

from . import (
    lfutil,
    localstore,
    wirestore,
)


# During clone this function is passed the src's ui object
# but it needs the dest's ui object so it can read out of
# the config file. Use repo.ui instead.
def openstore(repo=None, remote=None, put=False, ui=None):
    if ui is None:
        ui = repo.ui

    if not remote:
        lfpullsource = getattr(repo, 'lfpullsource', None)
        if put:
            path = urlutil.get_unique_push_path(
                b'lfpullsource', repo, ui, lfpullsource
            )
        else:
            path = urlutil.get_unique_pull_path_obj(
                b'lfpullsource', ui, lfpullsource
            )

        # XXX we should not explicitly pass b'default', as this will result in
        # b'default' being returned if no `paths.default` was defined. We
        # should explicitely handle the lack of value instead.
        if repo is None:
            path = urlutil.get_unique_pull_path_obj(
                b'lfs',
                ui,
                b'default',
            )
            remote = hg.peer(repo or ui, {}, path)
        elif path.loc == b'default-push' or path.loc == b'default':
            remote = repo
        else:
            remote = hg.peer(repo or ui, {}, path)

    # The path could be a scheme so use Mercurial's normal functionality
    # to resolve the scheme to a repository and use its path
    path = hasattr(remote, 'url') and remote.url() or remote.path

    match = _scheme_re.match(path)
    if not match:  # regular filesystem path
        scheme = b'file'
    else:
        scheme = match.group(1)

    try:
        storeproviders = _storeprovider[scheme]
    except KeyError:
        raise error.Abort(_(b'unsupported URL scheme %r') % scheme)

    for classobj in storeproviders:
        try:
            return classobj(ui, repo, remote)
        except lfutil.storeprotonotcapable:
            pass

    raise error.Abort(
        _(b'%s does not appear to be a largefile store')
        % urlutil.hidepassword(path)
    )


_storeprovider = {
    b'file': [localstore.localstore],
    b'http': [wirestore.wirestore],
    b'https': [wirestore.wirestore],
    b'ssh': [wirestore.wirestore],
}

_scheme_re = re.compile(br'^([a-zA-Z0-9+-.]+)://')


def getlfile(ui, hash):
    return util.chunkbuffer(openstore(ui=ui)._get(hash))