contrib/linux-wheel-centos5-blacklist

context: drop support for looking up context by ambiguous changeid (API)

This removes support for using the changectx constructor (and thereby
repo[x]) for looking up contexts by a stringified int, a namespace key
(e.g. a bookmark), or a partial hex nodeid. This means that
e.g. repo[<hex nodeid>] will now fail even if a bookmark with the same
name exists (which is a good thing IMO). It also means that doing
repo[<non-existent node>] no longer ends up loading namespaces (which
was a surprising side-effect of creating of failing to create a
context object that I recently ran into while debugging something
unrelated to this series).

Differential Revision: https://phab.mercurial-scm.org/D3449

test-convert-git.t
test-subrepo-git.t
test-patchbomb-tls.t