These are git hooks we have developed for the the official
PLplot git repo (server-side hooks and not useful on the client side)
and client-side hooks that can be voluntarily installed by our developers
on their local PLplot repos.

Client-side hooks:

None at this time.

Server-side hooks:

update When uploaded to the SF site, this enforces our current workflow rules
       by controlling what can be done using the push command.  The current
       rules are no merge commits are allowed, and no tag removal or
       reuse of a tag to point to a new commit is allowed.  Those rules
       on tags insure our history is preserved for all tags for our releases
       and special tags pointing to commits corresponding to the head of
       historical svn branches which have subsequently been deleted.