update
------
-This hook is invoked by `git-receive-pack`, which is invoked
-when a `git push` is done against the repository. It takes
-three parameters, name of the ref being updated, old object name
-stored in the ref, and the new objectname to be stored in the
-ref. Exiting with non-zero status from this hook prevents
-`git-receive-pack` from updating the ref.
-
-This can be used to prevent 'forced' update on certain refs by
+This hook is invoked by `git-receive-pack` on the remote repository,
+which is happens when a `git push` is done on a local repository.
+Just before updating the ref on the remote repository, the update hook
+is invoked. Its exit status determines the success or failure of
+the ref update.
+
+The hook executes once for each ref to be updated, and takes
+three parameters:
+ - the name of the ref being updated,
+ - the old object name stored in the ref,
+ - and the new objectname to be stored in the ref.
+
+A zero exit from the update hook allows the ref to be updated.
+Exiting with a non-zero status prevents `git-receive-pack`
+from updating the ref.
+
+This hook can be used to prevent 'forced' update on certain refs by
making sure that the object name is a commit object that is a
descendant of the commit object named by the old object name.
+That is, to enforce a "fast forward only" policy.
+
+It could also be used to log the old..new status. However, it
+does not know the entire set of branches, so it would end up
+firing one e-mail per ref when used naively, though.
+
Another use suggested on the mailing list is to use this hook to
implement access control which is finer grained than the one
based on filesystem group.
+The standard output of this hook is sent to /dev/null; if you
+want to report something to the git-send-pack on the other end,
+you can redirect your output to your stderr.
+
+
post-update
-----------
-This hook is invoked by `git-receive-pack`, which is invoked
-when a `git push` is done against the repository. It takes
-variable number of parameters; each of which is the name of ref
-that was actually updated.
+This hook is invoked by `git-receive-pack` on the remote repository,
+which is happens when a `git push` is done on a local repository.
+It executes on the remote repository once after all the refs have
+been updated.
+
+It takes a variable number of parameters, each of which is the
+name of ref that was actually updated.
This hook is meant primarily for notification, and cannot affect
the outcome of `git-receive-pack`.
+The post-update hook can tell what are the heads that were pushed,
+but it does not know what their original and updated values are,
+so it is a poor place to do log old..new.
+
The default post-update hook, when enabled, runs
`git-update-server-info` to keep the information used by dumb
-transport up-to-date.
+transports (e.g., http) up-to-date. If you are publishing
+a git repository that is accessible via http, you should
+probably enable this hook.
+
+The standard output of this hook is sent to /dev/null; if you
+want to report something to the git-send-pack on the other end,
+you can redirect your output to your stderr.