The main purpose of that pre-receive hook is to ensure that any push
updating the refs/meta/config reference only updates that one reference.
A large comment was added to the code to explain why (in short, this is
a pre-requisite for being able to use the git-hooks config at the same
time the config changes are being pushed).
While at it, to be consistent with the other hooks, support for
a repository-specific pre-receive hook is added. One side-effect
of this is that we end up trying to query the hooks configuration,
which triggers a check for the existence of the refs/meta/config
branch. As a result, an extra copy of the same warning gets generated
when the reference doesn't exist. This is not super elegant, but
isn't a problem in practice, since this is part of handling a deprecated
feature that we'll try to remove support for hopefully soon. In the
meantime, this isn't blocking to adding support for the pre-receive
option.
Since this commit increased the number of times `refs/meta/config`
was spelled out (aka "hardcoded"), this commit introduces a new
constant to avoid duplicating that special reference name.
Change-Id: Ib4fc0a32f639fe693e4d43269baf8c0838fc9214
TN: T227-003
