view mercurial/namespaces.py @ 34413:014d467f9d08

effectflag: store an empty effect flag for the moment

The idea behind effect flag is to store additional information in obs-markers
about what changed between a changeset and its successor(s). It's a low-level
information that comes without guarantees.

This information can be computed a posteriori, but only if we have all
changesets locally. This is not the case with distributed workflows where you
work with several people or on several computers (eg: laptop + build server).

Storing the effect-flag as a bitfield has several advantages:

- It's compact, we are using one byte per obs-marker at most for the effect-
  flag.
- It's compoundable, the obsfate log approach needs to display evolve history
  that could spans several obs-markers. Computing the effect-flag between a
  changeset and its grand-grand-grand-successor is simple thanks to the
  bitfield.

The effect-flag design has also some limitations:

- Evolving a changeset and reverting these changes just after would lead to
  two obs-markers with the same effect-flag without information that the first
  and third changesets are the same.

The effect-flag current design is a trade-off between compactness and
usefulness.

Storing this information helps commands to display a more complete and
understandable evolve history. For example, obslog (an Evolve command) use it
to improve its output:

x  62206adfd571 (34302) obscache: skip updating outdated obscache...
|    rewritten(parent) by Matthieu Laneuville <matthieu.laneuville@octobus...
|    rewritten(content) by Boris Feld <[e-mail]>

The effect flag is stored in obs-markers metadata while we iterate on the
information we want to store. We plan to extend the existing obsmarkers
bit-field when the effect flag design will be stabilized.

It's different from the CommitCustody concept, effect-flag are not signed and
can be forged. It's also different from the operation metadata as the command
name (for example: amend) could alter a changeset in different ways (changing
the content with hg amend, changing the description with hg amend -e, changing
the user with hg amend -U). Also it's compatible with every custom command
that writes obs-markers without needing to be updated.

The effect-flag is placed behind an experimental flag set to off by default.

Hook the saving of effect flag in create markers, but store only an empty one
for the moment, I will refine the values in effect flag in following patches.

For more information, see:

  https://www.mercurial-scm.org/wiki/ChangesetEvolutionDevel#Record_types_of_operation

Differential Revision: https://phab.mercurial-scm.org/D533

from __future__ import absolute_import

from .i18n import _
from . import (
    templatekw,
    util,
)

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 and operate on multiple namespaces. See
    the namespace class below for details on the namespace object.

    """

    _names_version = 0

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

        # we need current mercurial named objects (bookmarks, tags, and
        # branches) to be initialized somewhere, so that place is here
        bmknames = lambda repo: repo._bookmarks.keys()
        bmknamemap = lambda repo, name: tolist(repo._bookmarks.get(name))
        bmknodemap = lambda repo, node: repo.nodebookmarks(node)
        n = namespace("bookmarks", templatename="bookmark",
                      # i18n: column positioning for "hg log"
                      logfmt=_("bookmark:    %s\n"),
                      listnames=bmknames,
                      namemap=bmknamemap, nodemap=bmknodemap,
                      builtin=True)
        self.addnamespace(n)

        tagnames = lambda repo: [t for t, n in repo.tagslist()]
        tagnamemap = lambda repo, name: tolist(repo._tagscache.tags.get(name))
        tagnodemap = lambda repo, node: repo.nodetags(node)
        n = namespace("tags", templatename="tag",
                      # i18n: column positioning for "hg log"
                      logfmt=_("tag:         %s\n"),
                      listnames=tagnames,
                      namemap=tagnamemap, nodemap=tagnodemap,
                      deprecated={'tip'},
                      builtin=True)
        self.addnamespace(n)

        bnames = lambda repo: repo.branchmap().keys()
        bnamemap = lambda repo, name: tolist(repo.branchtip(name, True))
        bnodemap = lambda repo, node: [repo[node].branch()]
        n = namespace("branches", templatename="branch",
                      # i18n: column positioning for "hg log"
                      logfmt=_("branch:      %s\n"),
                      listnames=bnames,
                      namemap=bnamemap, nodemap=bnodemap,
                      builtin=True)
        self.addnamespace(n)

    def __getitem__(self, namespace):
        """returns the namespace object"""
        return self._names[namespace]

    def __iter__(self):
        return self._names.__iter__()

    def items(self):
        return self._names.iteritems()

    iteritems = items

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

        namespace: the name to be registered (in plural form)
        order: optional argument to specify the order of namespaces
               (e.g. 'branches' should be listed before 'bookmarks')

        """
        if order is not None:
            self._names.insert(order, namespace.name, namespace)
        else:
            self._names[namespace.name] = namespace

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

            templatekw.keywords[namespace.name] = 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)

class namespace(object):
    """provides an interface to a namespace

    Namespaces are basically 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 mapping of names to nodes, and a mapping from
    nodes to names. Each mapping returns a list.

    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.

    This namespace object will define the properties we need:
      'name': the namespace (plural form)
      'templatename': name to use for templating (usually the singular form
                      of the plural namespace name)
      'listnames': list of all names in the namespace (usually the keys of a
                   dictionary)
      'namemap': function that takes a name and returns a list of nodes
      'nodemap': function that takes a node and returns a list of names
      'deprecated': set of names to be masked for ordinary use
      'builtin': bool indicating if this namespace is supported by core
                 Mercurial.
    """

    def __init__(self, name, templatename=None, logname=None, colorname=None,
                 logfmt=None, listnames=None, namemap=None, nodemap=None,
                 deprecated=None, builtin=False):
        """create a namespace

        name: the namespace to be registered (in plural form)
        templatename: the name to use for templating
        logname: the name to use for log output; if not specified templatename
                 is used
        colorname: the name to use for colored log output; if not specified
                   logname is used
        logfmt: the format to use for (i18n-ed) log output; if not specified
                it is composed from logname
        listnames: function to list all names
        namemap: function that inputs a name, output node(s)
        nodemap: function that inputs a node, output name(s)
        deprecated: set of names to be masked for ordinary use
        builtin: whether namespace is implemented by core Mercurial
        """
        self.name = name
        self.templatename = templatename
        self.logname = logname
        self.colorname = colorname
        self.logfmt = logfmt
        self.listnames = listnames
        self.namemap = namemap
        self.nodemap = nodemap

        # if logname is not specified, use the template name as backup
        if self.logname is None:
            self.logname = self.templatename

        # if colorname is not specified, just use the logname as a backup
        if self.colorname is None:
            self.colorname = self.logname

        # if logfmt is not specified, compose it from logname as backup
        if self.logfmt is None:
            # i18n: column positioning for "hg log"
            self.logfmt = ("%s:" % self.logname).ljust(13) + "%s\n"

        if deprecated is None:
            self.deprecated = set()
        else:
            self.deprecated = deprecated

        self.builtin = builtin

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

    def nodes(self, repo, name):
        """method that returns a list of nodes in a namespace that
        match a given name.

        """
        return sorted(self.namemap(repo, name))