[PATCH 4 of 8] template: add minimal obsfate template function

[Yuya Nishihara]

On Tue, 08 Aug 2017 18:48:08 +0200, Boris Feld wrote:
> On Wed, 2017-08-09 at 00:19 +0900, Yuya Nishihara wrote:
> > On Mon, 07 Aug 2017 16:56:23 +0200, Boris Feld wrote:
> > > + at templatekeyword("succsandmarkers")
> > > +def showsuccsandmarkers(repo, ctx, **args):
> > > +    """Returns a list of dict for each final successor of ctx.
> > > +
> > > +    The dict contains successors node id in "successors" keys and
> > > the list of
> > > +    obs-markers from ctx to the set of successors in "markers"
> > > +    """
> > > +
> > > +    values = obsutil.successorsandmarkers(repo, ctx)
> > > +
> > > +    if values is None:
> > > +        values = []
> > > +
> > > +    return showlist('succsandmarkers', values, args)
> > 
> > I think returning a list of successor nodes is more natural.
> > 
> > Can we theoretically gather the relevant markers from successor
> > nodes?
> > If the "markers" field serves just as a cache, it could be stored in
> > revcache[] and passed to obsfate() under the hood.
> 
> The current algorithm for computing the successors sets of a changeset
> is this one:
> 
> Walk the obs-marker graph starting at a given revision. Follow
> successors of each revisions walked until revisions has no more
> successors, they are stable and they are the tip-most successor of the
> initial revision.
> 
> Having the sets of successors doesn't helps because a successor could
> be successor for more than one obsolete revision (fold for example).

Thanks for clarifying that. So markers are tied to each successorset?

  successorssets(rev) -> [(succs0, markers0), (succs1, markers1), ...]

In which case, {successorsset} could populate markers by makemap(),

  successorssets % "{successorset} {obsmarkers}"
                                   ^^^^^^^^^^^^
                               no idea how this should be rendered, but
                               let's revisit it later.

and perhaps obsfate could take the pair explicitly or implicitly.

  successorsets % "{obsfate(successorset, obsmarkers)}"  # a function
  successorsets % "{obsfate}"  # a keyword available only in successorsets

obsfate could be even split to verb/users/mindate/maxdate.

  successorsets % "{obsverb} {obsusers} ..."
                   ^^^^^^^^^^^^^^^^^^^^
                 these keyword functions may be populated by makemap(), too.

> The list of markers between a revisions and its successors could be
> cached, I'm not sure how to use revcache for that. Did you meant
> returning a hybrid object like this one, with a non-null revcache
> parameter: https://www.mercurial-scm.org/repo/hg/file/tip/mercurial/tem
> platekw.py#l641?

Something like showlatesttag() or showfile*() was in mind, but "revcache"
seems not the right tool as the markers aren't bound to the current rev.