comparison mercurial/obsolete.py @ 17774:0496d4f73cf4

obsolete: cheap detection of nullid as successors

Nullid as successors create multiple issues:

- Nullid revnum is -1, confusing algorithm that use revnum unless you add
  special handling in all of them.
- Nullid confuses "divergent" changeset detection and resolution. As you can't
  add any successors to Nullid without being in even more troubles

Fortunately, there is no good reason to use nullid as a successor. The only
sensible meaning of "succeed by nullid" is "dropped" and this meaning is already
covered by obsolescence marker with empty successors set.

However, letting some nullid successors to slip in may cause terrible damage in
such algorithm difficult to debug. So I prefer to perform and clear detection of
of such pathological changeset. We could be much smarter by cleaning up nullid
successors on the fly but it would be much for expensive. As core Mercurial does
not create any such changeset, I think it is fine to just abort when suspicious
situation is detected.

Earlier experimental version created such changesets, so there are some out
there.  The evolve extension added the necessary logic to clean up its mess.

17773:434e5bd615fc

  string contains a key and a value, separated by a color ':', without
  additional encoding. Keys cannot contain '\0' or ':' and values
  cannot contain '\0'.
"""
import struct
import util, base85
from i18n import _

_pack = struct.pack
_unpack = struct.unpack

            self._all.append(mark)
            pre, sucs = mark[:2]
            self.precursors.setdefault(pre, set()).add(mark)
            for suc in sucs:
                self.successors.setdefault(suc, set()).add(mark)

def _encodemarkers(markers, addheader=False):
    # Kept separate from flushmarkers(), it will be reused for
    # markers exchange.
    if addheader:

17774:0496d4f73cf4

  string contains a key and a value, separated by a color ':', without
  additional encoding. Keys cannot contain '\0' or ':' and values
  cannot contain '\0'.
"""
import struct
import util, base85, node
from i18n import _

_pack = struct.pack
_unpack = struct.unpack

            self._all.append(mark)
            pre, sucs = mark[:2]
            self.precursors.setdefault(pre, set()).add(mark)
            for suc in sucs:
                self.successors.setdefault(suc, set()).add(mark)
        if node.nullid in self.successors:
            raise util.Abort(_('bad obsolescence marker detected: '
                               'invalid successors nullid'))

def _encodemarkers(markers, addheader=False):
    # Kept separate from flushmarkers(), it will be reused for
    # markers exchange.
    if addheader: