wireprotov2: define and implement "changesetdata" command
This commit introduces the "changesetdata" wire protocol command.
The role of the command is to expose data associated with changelog
revisions, including the raw revision data itself.
This command is the first piece of a new clone/pull strategy that
is built on top of domain-specific commands for data retrieval.
Instead of a monolithic "getbundle" command that transfers all of the
things, we'll be introducing commands for fetching specific pieces
of data.
Since the changeset is the fundamental unit from which we derive
pointers to other data (manifests, file nodes, etc), it makes sense
to start reimplementing pull with this data.
The command accepts as arguments a set of root and head revisions
defining the changesets that should be fetched as well as an explicit
list of nodes. By default, the command returns only the node values:
the client must explicitly request additional fields be added to the
response. Current supported fields are the list of parent nodes and
the revision fulltext.
My plan is to eventually add support for transferring other data
associated with changesets, including phases, bookmarks, obsolescence
markers, etc. Since the response format is CBOR, we'll be able to add
this data into the response object relatively easily (it should be
as simple as adding a key in a map).
The documentation captures a number of TODO items. Some of these may
require BC breaking changes. That's fine: wire protocol v2 is still
highly experimental.
Differential Revision: https://phab.mercurial-scm.org/D4481
# state.py - writing and reading state files in Mercurial
#
# Copyright 2018 Pulkit Goyal <pulkitmgoyal@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""
This file contains class to wrap the state for commands and other
related logic.
All the data related to the command state is stored as dictionary in the object.
The class has methods using which the data can be stored to disk in a file under
.hg/ directory.
We store the data on disk in cbor, for which we use the third party cbor library
to serialize and deserialize data.
"""
from __future__ import absolute_import
from . import (
error,
util,
)
from .utils import (
cborutil,
)
class cmdstate(object):
"""a wrapper class to store the state of commands like `rebase`, `graft`,
`histedit`, `shelve` etc. Extensions can also use this to write state files.
All the data for the state is stored in the form of key-value pairs in a
dictionary.
The class object can write all the data to a file in .hg/ directory and
can populate the object data reading that file.
Uses cbor to serialize and deserialize data while writing and reading from
disk.
"""
def __init__(self, repo, fname):
""" repo is the repo object
fname is the file name in which data should be stored in .hg directory
"""
self._repo = repo
self.fname = fname
def read(self):
"""read the existing state file and return a dict of data stored"""
return self._read()
def save(self, version, data):
"""write all the state data stored to .hg/<filename> file
we use third-party library cbor to serialize data to write in the file.
"""
if not isinstance(version, int):
raise error.ProgrammingError("version of state file should be"
" an integer")
with self._repo.vfs(self.fname, 'wb', atomictemp=True) as fp:
fp.write('%d\n' % version)
for chunk in cborutil.streamencode(data):
fp.write(chunk)
def _read(self):
"""reads the state file and returns a dictionary which contain
data in the same format as it was before storing"""
with self._repo.vfs(self.fname, 'rb') as fp:
try:
int(fp.readline())
except ValueError:
raise error.CorruptedState("unknown version of state file"
" found")
return cborutil.decodeall(fp.read())[0]
def delete(self):
"""drop the state file if exists"""
util.unlinkpath(self._repo.vfs.join(self.fname), ignoremissing=True)
def exists(self):
"""check whether the state file exists or not"""
return self._repo.vfs.exists(self.fname)