[PATCH 0/5] Multiple hook support

["brian m. carlson" <sandals@crustytoothpaste.net>]

Oftentimes, people want to use multiple of the same kind of hook. This
may be because software or a project they use requires a given hook, but
they would also like to have a custom hook, or because they're using
multiple pieces of software that both require involvement with the same
hook.

This series introduces support for multiple hooks by using a ".d"
directory. For example, instead of using a single
".git/hooks/post-checkout" file, you'd use multiple files within
".git/hooks/post-checkout.d". This is the standard Unix paradigm for
multiple files and should be familiar to most people. Hooks are executed
in sorted order.

To preserve backwards compatibility, we don't run the hooks in the ".d"
directory if the single file is a valid hook (i.e. it exists and is
executable). This is because some people already have multiple hook
scripts configured, and if we ran them both, we'd run the hooks twice.
This would be bad for e.g. the prepare-commit-msg hook. This is also the
least surprising behavior.

We check each hook for its exit status, even if the hook normally
ignores exit status, and if it fails, we abort executing further hooks.
This provides an easy way to reason about what the exit status is when a
hook fails; we need not consider how to handle multiple failing hooks.
It's also consistent among all hooks, whether they care about exit
status or not.

This series uses a test library to verify that we run the hooks for each
command instead of writing the same tests multiple times. If there are
other cases you'd like to see, please let me know.

I've talked with some people about this approach, and they've indicated
they would prefer a configuration-based approach. I've tried to make the
series such that it can be replaced with such an approach if that's the
decision we make. It should be easy enough to simply replace find_hooks
with an appropriate implementation and update the test framework.

brian m. carlson (5):
  run-command: add preliminary support for multiple hooks
  builtin/receive-pack: add support for multiple hooks
  sequencer: add support for multiple hooks
  builtin/worktree: add support for multiple post-checkout hooks
  transport: add support for multiple pre-push hooks

 builtin/am.c                       |  28 ++--
 builtin/commit.c                   |   5 +-
 builtin/receive-pack.c             | 212 +++++++++++++++++------------
 builtin/worktree.c                 |  40 ++++--
 run-command.c                      | 117 ++++++++++++----
 run-command.h                      |   9 +-
 sequencer.c                        |  96 ++++++++-----
 t/lib-hooks.sh                     | 156 +++++++++++++++++++++
 t/t5403-post-checkout-hook.sh      |   8 ++
 t/t5407-post-rewrite-hook.sh       |  15 ++
 t/t5516-fetch-push.sh              |  29 ++++
 t/t5571-pre-push-hook.sh           |  19 +++
 t/t7503-pre-commit-hook.sh         |  15 ++
 t/t7505-prepare-commit-msg-hook.sh |   9 ++
 transport.c                        |  98 +++++++------
 15 files changed, 636 insertions(+), 220 deletions(-)
 create mode 100644 t/lib-hooks.sh