[PATCH 3 of 3 V3] localrepo: better error message when revlog error and file addition (issue4675)

[Jordi Gutiérrez Hermoso]

On Wed, 2015-06-03 at 15:20 -0500, Matt Mackall wrote:
> On Tue, 2015-06-02 at 15:07 -0400, Jordi Gutiérrez Hermoso wrote:
> > # HG changeset patch
> > # User Jordi Gutiérrez Hermoso <jordigh at octave.org>
> > # Date 1432239912 14400
> > #      Thu May 21 16:25:12 2015 -0400
> > # Node ID 6299517509f9a8912ff83fffa46cecf964ba779c
> > # Parent  3353bc00fbb14f2930cf0e9b72be312e578d2f6e
> > localrepo: better error message when revlog error and file addition (issue4675)
> > 
> > At this level we have enough context for saying which filename caused
> > the revlog error, and we can also add the hint from the revlog
> > exception, if any.
> > 
> > diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
> > --- a/mercurial/localrepo.py
> > +++ b/mercurial/localrepo.py
> > @@ -1348,7 +1348,10 @@ class localrepository(object):
> >          text = fctx.data()
> >          if fparent2 != nullid or flog.cmp(fparent1, text) or meta:
> >              changelist.append(fname)
> > -            return flog.add(text, meta, tr, linkrev, fparent1, fparent2)
> > +            try:
> > +                return flog.add(text, meta, tr, linkrev, fparent1, fparent2)
> > +            except error.RevlogError as exc:
> > +                raise util.Abort("%s: %s" % (exc, fname), hint=exc.hint)
> >          # are just the flags changed during merge?
> >          elif fname in manifest1 and manifest1.flags(fname) != fctx.flags():
> >              changelist.append(fname)
> 
> Looks like the wrong layer for this. Either belongs in
> revlog._addrevision (where it'll catch changelog and manifest overflows
> too)

I thought it would make most sense to catch manifest overflows
elsewhere, not in revlog.py. We need more context in order to form an
error message about how the problem is about too many files, not a
single large file.

Which makes me think that the largefiles hint should also be added at
localrepo, but then the exception raised by revlogio should be
something more specific than RevlogError. Are we ok with
RevlogOverflow or something like it?

> or filelog.add.

There isn't a filename here to add to the error message, although I
suppose I could compute the filename from the revlog's file name. Is
there a simple way to do that, or do I need to consult the manifest?
Will there already be a manifest at this stage if the file is being
newly added?