sshpeer: initial definition and implementation of new SSH protocol
The existing SSH protocol has several design flaws. Future commits
will elaborate on these flaws as new features are introduced
to combat these flaws. For now, hopefully you can take me for my
word that a ground up rewrite of the SSH protocol is needed.
This commit lays the foundation for a new SSH protocol by defining
a mechanism to upgrade the SSH transport channel away from the
default (version 1) protocol to something modern (which we'll call
"version 2" for now).
This upgrade process is detailed in the internals documentation
for the wire protocol. The gist of it is the client sends a
request line preceding the "hello" command/line which basically
says "I'm requesting an upgrade: here's what I support." If the
server recognizes that line, it processes the upgrade request and
the transport channel is switched to use the new version of the
protocol. If not, it sends an empty response, which is how all
Mercurial SSH servers from the beginning of time reacted to unknown
commands. The upgrade request is effectively ignored and the client
continues to use the existing version of the protocol as if nothing
happened.
The new version of the SSH protocol is completely identical to
version 1 aside from the upgrade dance and the bytes that follow.
The immediate bytes that follow the protocol switch are defined to
be a length framed "capabilities: " line containing the remote's
advertised capabilities. In reality, this looks very similar to
what the "hello" response would look like. But it will evolve
quickly.
The methodology by which the protocol will evolve is important.
I'm not going to introduce the new protocol all at once. That would
likely lead to endless bike shedding and forward progress would
stall. Instead, I intend to tricle out new features and diversions
from the existing protocol in small, incremental changes.
To support the gradual evolution of the protocol, the on-the-wire
advertised protocol name contains an "exp" to denote "experimental"
and a 4 digit field to capture the sub-version of the protocol.
Whenever we make a BC change to the wire protocol, we can increment
this version and lock out all older clients because it will appear
as a completely different protocol version. This means we can incur
as many breaking changes as we want. We don't have to commit to
supporting any one feature or idea for a long period of time. We
can even evolve the handshake mechanism, because that is defined
as being an implementation detail of the negotiated protocol version!
Hopefully this lowers the barrier to accepting changes to the
protocol and for experimenting with "radical" ideas during its
development.
In core, sshpeer received most of the attention. We haven't even
implemented the server bits for the new protocol in core yet.
Instead, we add very primitive support to our test server, mainly
just to exercise the added code paths in sshpeer.
Differential Revision: https://phab.mercurial-scm.org/D2061
# no-check-commit because of required foo_bar naming
# Copyright (C) 2006 - Marco Barisione <marco@barisione.org>
#
# This is a small extension for Mercurial (https://mercurial-scm.org/)
# that removes files not known to mercurial
#
# This program was inspired by the "cvspurge" script contained in CVS
# utilities (http://www.red-bean.com/cvsutils/).
#
# For help on the usage of "hg purge" use:
# hg help purge
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>.
'''command to delete untracked files from the working directory'''
from __future__ import absolute_import
import os
from mercurial.i18n import _
from mercurial import (
cmdutil,
error,
registrar,
scmutil,
util,
)
cmdtable = {}
command = registrar.command(cmdtable)
# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'
@command('purge|clean',
[('a', 'abort-on-err', None, _('abort if an error occurs')),
('', 'all', None, _('purge ignored files too')),
('', 'dirs', None, _('purge empty directories')),
('', 'files', None, _('purge files')),
('p', 'print', None, _('print filenames instead of deleting them')),
('0', 'print0', None, _('end filenames with NUL, for use with xargs'
' (implies -p/--print)')),
] + cmdutil.walkopts,
_('hg purge [OPTION]... [DIR]...'))
def purge(ui, repo, *dirs, **opts):
'''removes files not tracked by Mercurial
Delete files not known to Mercurial. This is useful to test local
and uncommitted changes in an otherwise-clean source tree.
This means that purge will delete the following by default:
- Unknown files: files marked with "?" by :hg:`status`
- Empty directories: in fact Mercurial ignores directories unless
they contain files under source control management
But it will leave untouched:
- Modified and unmodified tracked files
- Ignored files (unless --all is specified)
- New files added to the repository (with :hg:`add`)
The --files and --dirs options can be used to direct purge to delete
only files, only directories, or both. If neither option is given,
both will be deleted.
If directories are given on the command line, only files in these
directories are considered.
Be careful with purge, as you could irreversibly delete some files
you forgot to add to the repository. If you only want to print the
list of files that this program would delete, use the --print
option.
'''
act = not opts.get('print')
eol = '\n'
if opts.get('print0'):
eol = '\0'
act = False # --print0 implies --print
removefiles = opts.get('files')
removedirs = opts.get('dirs')
if not removefiles and not removedirs:
removefiles = True
removedirs = True
def remove(remove_func, name):
if act:
try:
remove_func(repo.wjoin(name))
except OSError:
m = _('%s cannot be removed') % name
if opts.get('abort_on_err'):
raise error.Abort(m)
ui.warn(_('warning: %s\n') % m)
else:
ui.write('%s%s' % (name, eol))
match = scmutil.match(repo[None], dirs, opts)
if removedirs:
directories = []
match.explicitdir = match.traversedir = directories.append
status = repo.status(match=match, ignored=opts.get('all'), unknown=True)
if removefiles:
for f in sorted(status.unknown + status.ignored):
if act:
ui.note(_('removing file %s\n') % f)
remove(util.unlink, f)
if removedirs:
for f in sorted(directories, reverse=True):
if match(f) and not os.listdir(repo.wjoin(f)):
if act:
ui.note(_('removing directory %s\n') % f)
remove(os.rmdir, f)