[PATCH 6 of 7] context: introduce a `_findchangeid` method to `filectx`

[Boris FELD]

On 07/09/2018 11:17, Martin von Zweigbergk via Mercurial-devel wrote:
>
>
> On Fri, Sep 7, 2018 at 8:13 AM Boris Feld <boris.feld at octobus.net 
> <mailto:boris.feld at octobus.net>> wrote:
>
>     # HG changeset patch
>     # User Boris Feld <boris.feld at octobus.net
>     <mailto:boris.feld at octobus.net>>
>     # Date 1536255775 14400
>     #      Thu Sep 06 13:42:55 2018 -0400
>     # Node ID 441c39342d63c75ee101587b2fbf3af60800762f
>     # Parent  f74f706f6d061cf9369cd45caa3a71d3fc03b293
>     # EXP-Topic copy-perf
>     # Available At https://bitbucket.org/octobus/mercurial-devel/
>     #              hg pull
>     https://bitbucket.org/octobus/mercurial-devel/ -r 441c39342d63
>     context: introduce a `_findchangeid` method to `filectx`
>
>     In the same spirit as `_introrev` we want to introduce a way to
>     limit graph
>     walking when resolving `filectx.rev()`.
>
>
> Can you elaborate? I know what introrev() does.
We tried giving more details in the previous commit:

     We want to add a mechanism to stop iteration early associated to
     intro rev early in some case. However, it does not make sense to
     expose it in the public `filectx` API. So we split the code into an
     internal method instead.

Instead of modifying the `_changeid` property, we move most of the code 
in a new low-level method.

In the next commit, we modify this new low-level method to introduce the 
walk limitation.
>
>     We introduce a new internal function for
>     this purpose.
>
>     diff --git a/mercurial/context.py b/mercurial/context.py
>     --- a/mercurial/context.py
>     +++ b/mercurial/context.py
>     @@ -631,16 +631,21 @@ class basefilectx(object):
>
>          @propertycache
>          def _changeid(self):
>     +        return self._findchangeid()
>     +
>     +    def _findchangeid(self):
>
>
> If it's always going to return a revnum (never a nodeid), can we call 
> it _findchangrev() instead?

Yes, should we send a V2 or could it be fixed inflight?
>
>              if r'_changeid' in self.__dict__:
>     -            return self._changeid
>     +            changeid = self._changeid
>              elif r'_changectx' in self.__dict__:
>     -            return self._changectx.rev()
>     +            changeid = self._changectx.rev()
>              elif r'_descendantrev' in self.__dict__:
>                  # this file context was created from a revision with
>     a known
>                  # descendant, we can (lazily) correct for linkrev aliases
>     -            return self._adjustlinkrev(self._descendantrev)
>     +            changeid = self._adjustlinkrev(self._descendantrev)
>              else:
>     -            return self._filelog.linkrev(self._filerev)
>     +            changeid = self._filelog.linkrev(self._filerev)
>     +        self._changeid = changeid
>     +        return changeid
>
>          @propertycache
>          def _filenode(self):
>     @@ -872,7 +877,7 @@ class basefilectx(object):
>                  else:
>                      return self._adjustlinkrev(lazyrev, inclusive=True)
>              else:
>     -            return self.rev()
>     +            return self._findchangeid()
>
>          def introfilectx(self):
>              """Return filectx having identical contents, but pointing
>     to the
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