[PATCH 6 of 6] hidden: alert hidden store when obsmarkers are created

[Durham Goode]

On 5/18/17 11:24 AM, Durham Goode wrote:
> # HG changeset patch
> # User Durham Goode <durham at fb.com>
> # Date 1495129620 25200
> #      Thu May 18 10:47:00 2017 -0700
> # Node ID b09fa310c34bdbad4fc2b5b914e84e0fc9dc4b68
> # Parent  0979ce9d40803103441b6df1ebefafe80bb9a057
> hidden: alert hidden store when obsmarkers are created
>
> This calls the new updatevisibility function from obsolete.createmarkers(). This
> let's us update the currently stored hidden information when markers change.
>
> diff --git a/mercurial/obsolete.py b/mercurial/obsolete.py
> --- a/mercurial/obsolete.py
> +++ b/mercurial/obsolete.py
> @@ -1226,6 +1226,7 @@ def createmarkers(repo, relations, flag=
>          metadata['user'] = repo.ui.username()
>      tr = repo.transaction('add-obsolescence-marker')
>      try:
> +        affectednodes = set()
>          markerargs = []
>          for rel in relations:
>              prec = rel[0]
> @@ -1258,6 +1259,11 @@ def createmarkers(repo, relations, flag=
>              repo.obsstore.create(tr, nprec, nsucs, flag, parents=npare,
>                                   date=date, metadata=localmetadata)
>              repo.filteredrevcache.clear()
> +            affectednodes.add(nprec)
> +
> +        cl = repo.unfiltered().changelog
> +        affectedrevs = (cl.rev(n) for n in affectednodes if n in cl.nodemap)
> +        repo.hidden.updatevisibility(affectedrevs)
>          tr.close()
>      finally:
>          tr.release()

This is the first half of a series that introduces the concept of an 
explicit hidden store.  It is represented as a set, where you can test 
if a given commit is hidden or not, and is serialized as a set of roots 
of the hidden part of the graph.

It is currently just a cache of the current hidden algorithm, and the 
final patch in the series (not sent yet) adds validation that the hidden 
store always matches the computehidden result.

Other parts of Mercurial communicate with the hidden store simply by 
telling it what nodes they've touched 
(`repo.hidden.updatevisibility(affectedrevs)`), so knowledge about the 
exact hidden semantics remains confined to hidden.py.

This direction has several benefits:
- moves the computation of hiddeness to write-time instead of read-time, 
so we only have to pay it once
- enables external extensions to interact with hidden computations more 
easily (they can now observe hidden affecting changes by wrapping the 
updatevisibility function, without having to individually monkey patch 
into bookmarks/tags/obsmarkers/etc)
- potentially gives us future flexibility on the defining and storing 
what is hidden and what is not