[PATCH 2 of 2 V2] server: introduce a 'experimental.single-head-per-branch' option

[Augie Fackler]

On Mon, Nov 20, 2017 at 06:15:22PM +0100, Boris Feld wrote:
> # HG changeset patch
> # User Boris Feld <boris.feld at octobus.net>
> # Date 1510800762 -3600
> #      Thu Nov 16 03:52:42 2017 +0100
> # Node ID 2d706154205c1fbff7ad5baea90697c7848ad61c
> # Parent  5312b5738172718b868c1ecfd28ada8d4d7e85de
> # EXP-Topic single-heads
> # Available At https://bitbucket.org/octobus/mercurial-devel/
> #              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r 2d706154205c
> server: introduce a 'experimental.single-head-per-branch' option

Convince me this should be done like this rather than as an example
hook? We've wanted example hooks in contrib/example-hooks for years,
maybe this would be a good start.