view hgext/fsmonitor/pywatchman/capabilities.py @ 35506:fa865878a849

lfs: show a friendly message when pushing lfs to a server without lfs enabled

Upfront disclaimer: I don't know anything about the wire protocol, and this was
pretty much cargo-culted from largefiles, and then clonebundles, since it seems
more modern.  I was surprised that exchange.push() will ensure all of the proper
requirements when exchanging between two local repos, but doesn't care when one
is remote.

All this new capability marker does is inform the client that the extension is
enabled remotely.  It may or may not contain commits with external blobs.

Open issues:

  - largefiles uses 'largefiles=serve' for its capability.  Someday I hope to
    be able to push lfs blobs to an `hg serve` instance.  That will probably
    require a distinct capability.  Should it change to '=serve' then?  Or just
    add an 'lfs-serve' capability then?

  - The flip side of this is more complicated.  It looks like largefiles adds an
    'lheads' command for the client to signal to the server that the extension
    is loaded.  That is then converted to 'heads' and sent through the normal
    wire protocol plumbing.  A client using the 'heads' command directly is
    kicked out with a message indicating that the largefiles extension must be
    loaded.  We could do similar with 'lfsheads', but then a repo with both
    largefiles and lfs blobs can't be pushed over the wire.  Hopefully somebody
    with more wire protocol experience can think of something else.  I see
    'x-hgarg-1' on some commands in the tests, but not on heads, and didn't dig
    any further.

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from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
# no unicode literals

import re

def parse_version(vstr):
    res = 0
    for n in vstr.split('.'):
        res = res * 1000
        res = res + int(n)
    return res

cap_versions = {
    "cmd-watch-del-all": "3.1.1",
    "cmd-watch-project": "3.1",
    "relative_root": "3.3",
    "term-dirname": "3.1",
    "term-idirname": "3.1",
    "wildmatch": "3.7",
}

def check(version, name):
    if name in cap_versions:
        return version >= parse_version(cap_versions[name])
    return False

def synthesize(vers, opts):
    """ Synthesize a capability enabled version response
        This is a very limited emulation for relatively recent feature sets
    """
    parsed_version = parse_version(vers['version'])
    vers['capabilities'] = {}
    for name in opts['optional']:
        vers['capabilities'][name] = check(parsed_version, name)
    failed = False
    for name in opts['required']:
        have = check(parsed_version, name)
        vers['capabilities'][name] = have
        if not have:
            vers['error'] = 'client required capability `' + name + \
                            '` is not supported by this server'
    return vers