Revert "Implementation of manifest defined githooks"

This reverts commit 38e4387f8eb8cffd6359d726c38a7c524fef07e3.

A "repo init" followed by "repo sync" is meant to be as safe as
"git clone".  In particular it should not run arbitrary code provided
by the manifest owner.

It would still be nice to have support for manifest-defined git hooks
--- they'd just need a prompt like the upload RepoHook has.  Hopefully
a later change can bring them back.

Change-Id: I5ecd90fb5c2ed64f103d856d1ffcba38a47b062d
Signed-off-by: Jonathan Nieder <jrn@google.com>
4 files changed