mercurial/namespaces.py

merge: introduce 'c' action like 'g', but with additional safety

_checkunknownfile() reads the filelog of the remote side's file. For
narrow clones, the filelog will not exist for all files and we need a
way to avoid reading them. While it would be easier for the narrow
extension to just override _checkunknownfile() and make it ignore
files outside the narrow clone, it seems cleaner to have
manifestmerge() not care about filelogs (considering its
name).

In order to move the calls to _checkunknownfile() out, we need to be
able to tell in which cases we should check for unknown files. Let's
start by introducing a new action distinct from 'g' for this
purpose. Specifically, the new action will be just like 'g' except
that it will check that for conflicting unknown files first. For now,
just add the new action type and convert it to 'g'.

from i18n import _
from mercurial import util
import templatekw

def tolist(val):
    """
    a convenience method to return an empty list instead of None
    """
    if val is None:
        return []
    else:
        return [val]

class namespaces(object):
    """
    provides an interface to register a generic many-to-many mapping between
    some (namespaced) names and nodes. The goal here is to control the
    pollution of jamming things into tags or bookmarks (in extension-land) and
    to simplify internal bits of mercurial: log output, tab completion, etc.

    More precisely, we define a list of names (the namespace), a mapping of
    names to nodes, and a mapping from nodes to names. Each mapping
    returns a list of nodes.

    Furthermore, each name mapping will be passed a name to lookup which might
    not be in its domain. In this case, each method should return an empty list
    and not raise an error.

    We'll have a dictionary '_names' where each key is a namespace and
    its value is a dictionary of functions:
      'templatename': name to use for templating (usually the singular form
                      of the plural namespace name)
      'namemap': function that takes a name and returns a list of nodes
      'nodemap': function that takes a node and returns a list of names
    """

    _names_version = 0

    def __init__(self):
        self._names = util.sortdict()

        addns = self.addnamespace

        # we need current mercurial named objects (bookmarks, tags, and
        # branches) to be initialized somewhere, so that place is here
        addns("bookmarks", "bookmark",
              lambda repo, name: tolist(repo._bookmarks.get(name)),
              lambda repo, name: repo.nodebookmarks(name))

        addns("tags", "tag",
              lambda repo, name: tolist(repo._tagscache.tags.get(name)),
              lambda repo, name: repo.nodetags(name))

        addns("branches", "branch",
              lambda repo, name: tolist(repo.branchtip(name)),
              lambda repo, node: [repo[node].branch()])

    def addnamespace(self, namespace, templatename, namemap, nodemap,
                     order=None):
        """
        register a namespace

        namespace: the name to be registered (in plural form)
        templatename: the name to use for templating
        namemap: function that inputs a node, output name(s)
        nodemap: function that inputs a name, output node(s)
        order: optional argument to specify the order of namespaces
               (e.g. 'branches' should be listed before 'bookmarks')
        """
        val = {'templatename': templatename,
               'namemap': namemap,
               'nodemap': nodemap}
        if order is not None:
            self._names.insert(order, namespace, val)
        else:
            self._names[namespace] = val

        # we only generate a template keyword if one does not already exist
        if namespace not in templatekw.keywords:
            def generatekw(**args):
                return templatekw.shownames(namespace, **args)

            templatekw.keywords[namespace] = generatekw

    def singlenode(self, repo, name):
        """
        Return the 'best' node for the given name. Best means the first node
        in the first nonempty list returned by a name-to-nodes mapping function
        in the defined precedence order.

        Raises a KeyError if there is no such node.
        """
        for ns, v in self._names.iteritems():
            n = v['namemap'](repo, name)
            if n:
                # return max revision number
                if len(n) > 1:
                    cl = repo.changelog
                    maxrev = max(cl.rev(node) for node in n)
                    return cl.node(maxrev)
                return n[0]
        raise KeyError(_('no such name: %s') % name)

    def templatename(self, namespace):
        """method that returns the template name of a namespace"""
        return self._names[namespace]['templatename']

    def names(self, repo, namespace, node):
        """method that returns a (sorted) list of names in a namespace that
        match a given node"""
        return sorted(self._names[namespace]['nodemap'](repo, node))