[PATCH 3 of 6] py3: implement __lt__() to make gitlfspointer sortable

[Yuya Nishihara]

On Sun, 30 Sep 2018 09:20:15 -0400, Matt Harbison wrote:
> > On Sep 30, 2018, at 8:08 AM, Yuya Nishihara <yuya at tcha.org> wrote:
> > 
> >> On Sun, 30 Sep 2018 01:46:22 -0400, Matt Harbison wrote:
> >> # HG changeset patch
> >> # User Matt Harbison <matt_harbison at yahoo.com>
> >> # Date 1538278134 14400
> >> #      Sat Sep 29 23:28:54 2018 -0400
> >> # Node ID 96752a0137b4b08677f3205362ece3c2e7fde057
> >> # Parent  1dd7c3dcfb46a39bc61419415c0818e0ed1bbd1c
> >> py3: implement __lt__() to make gitlfspointer sortable
> >> 
> >> diff --git a/hgext/lfs/pointer.py b/hgext/lfs/pointer.py
> >> --- a/hgext/lfs/pointer.py
> >> +++ b/hgext/lfs/pointer.py
> >> @@ -30,6 +30,9 @@ class gitlfspointer(dict):
> >>         super(gitlfspointer, self).__init__(*args)
> >>         self.update(pycompat.byteskwargs(kwargs))
> >> 
> >> +    def __lt__(self, other):
> >> +        return self.oid() < other.oid()
> > 
> > I don't think it's correct to implement only __lt__(). Perhaps, easier
> > workaround is to use sorted(..., key=lambda...) instead.
> 
> The SO post I saw implemented __eq__() too, but then that usually means needing a hash function too.

Yes.

> I didn’t go the route of specifying the sorted() key, because it seems too easy to forget to do that in each place.  (And harder to find each place now.)

Maybe we can run the test with __le__() that raises Exception? It's probably
wrong to sort pointers in memory address order.

To support partial ordering, we'll probably need to implement le, lt, ge, gt.