Merge branch 'ab/config-based-hooks-2'

More "config-based hooks". * ab/config-based-hooks-2: run-command: remove old run_hook_{le,ve}() hook API receive-pack: convert push-to-checkout hook to hook.h read-cache: convert post-index-change to use hook.h commit: convert {pre-commit,prepare-commit-msg} hook to hook.h git-p4: use 'git hook' to run hooks send-email: use 'git hook run' for 'sendemail-validate' git hook run: add an --ignore-missing flag hooks: convert worktree 'post-checkout' hook to hook library hooks: convert non-worktree 'post-checkout' hook to hook library merge: convert post-merge to use hook.h am: convert applypatch-msg to use hook.h rebase: convert pre-rebase to use hook.h hook API: add a run_hooks_l() wrapper am: convert {pre,post}-applypatch to use hook.h gc: use hook library for pre-auto-gc hook hook API: add a run_hooks() wrapper hook: add 'run' subcommand