contrib/xml.rnc

phabricator: add a `phabimport` command

I've had `alias.phabimport = $hg phabread --stack $1 | $hg import --bypass -`
for a while now, and I suspect others do too.  That's limited though, in that it
can't use the information on Phabricator to restore it in the original location,
so I'm making it a first class command.

This doesn't do anything ambitious like that- this is mostly a simplification of
`hg import` to get the equivalent of the alias mentioned above.  The `--bypass`
option is hardcoded to be enabled and the message about amending rejects
dropped (rejects aren't created with `--bypass`), because editing patches on
Phabricator seems like an unusual workflow.

This will need other options, like `--obsolete` and `--secret`.  I think these
would be more useful as config settings, as I imagine the workflows are pretty
fixed depending on roles.  Reviewers who don't queue patches probably never want
`--obsolete`, but may need `--secret`.  Reviewers who do will want the former,
but not the latter.  I left `--stack` as an option, but that should probably be
a config knob too (or at least default to on)- if the point of this is to avoid
rejects, it doesn't make sense to skip dependencies in most cases.

Evolve is going to need a fix to its wrapping of `cmdutil.tryimportone()`, as it
currently assumes `opts` has an `obsolete` key.  It's worked around for now.

Differential Revision: https://phab.mercurial-scm.org/D8136

# RelaxNG schema for "xml" log style
# Inspired by Subversion's XML log format.

start = log
node.type = xsd:string  {minLength = "40" maxLength = "40"}

log = element log { logentry+ }
logentry = element logentry {
    logentry.attlist,
    branch*, tag*, hgparent*,
    author, date,
    msg, paths?, copies?, extra*
}
logentry.attlist =
    attribute revision {xsd:nonNegativeInteger}
  & attribute node {node.type}
branch = element branch { text }
tag = element tag { text }
hgparent = element parent {hgparent.attlist, text}
hgparent.attlist =
    attribute revision {xsd:integer {minInclusive = "-1"} }
  & attribute node {node.type}
author = element author { author.attlist, text }
author.attlist =
    attribute email {text}
date = element date {xsd:dateTime}
msg = element msg {msg.attlist, text}
msg.attlist =
    attribute xml:space {"preserve"}
paths = element paths { path* }
path = element path { path.attlist, text }
path.attlist =
    # Action: (A)dd, (M)odify, (R)emove
    attribute action {"A"|"M"|"R"}
copies = element copies { copy+ }
copy = element copy { copy.attlist, text }
copy.attlist =
    attribute source {text}
extra = element extra {extra.attlist, text}
extra.attlist =
    attribute key {text}