#!/bin/sh
# Prepare the dev environment for a new checkout or worktree.
#
# Installed into the git hooks directory by script/setup. Deliberately tiny and
# self-contained: it stays valid on branches where script/setup does not exist,
# and simply does nothing there.

# $3 is 1 for a branch checkout, 0 for a file checkout.
[ "$3" = "1" ] || exit 0

top=$(git rev-parse --show-toplevel 2>/dev/null) || exit 0

# This also runs on ordinary branch switches, where there is nothing to do.
[ -x "$top/venv/bin/python" ] && exit 0
[ -x "$top/script/setup" ] || exit 0

# Every worktree shares the hooks directory of the checkout it was created
# from, and the script/setup run below is the one from whichever branch was just
# checked out. Older branches install their own pre-commit hook without checking
# for a worktree: that moves the shared hook aside as pre-commit.legacy and
# replaces it with one tied to this worktree's virtual environment, so commits
# break in every checkout. To rule that out, the hooks directory is copied
# before script/setup runs and put back exactly as it was afterwards, including
# removing any file script/setup added.
hooks=$(git rev-parse --path-format=absolute --git-path hooks 2>/dev/null) || exit 0
snap=$(mktemp -d "$hooks/.post-checkout.XXXXXX") || exit 0
cp -p "$hooks"/* "$snap"/ 2>/dev/null

# Clear VIRTUAL_ENV so a checkout made from a shell with an environment already
# activated still gets its own, rather than having the active one repointed at
# this working tree.
env -u VIRTUAL_ENV "$top/script/setup"
status=$?

for f in "$hooks"/*; do
  [ -e "$snap/${f##*/}" ] || rm -f "$f"
done
# Files are moved rather than copied so a hook that is still running, such as
# this one, is swapped out atomically instead of being rewritten in place.
for f in "$snap"/*; do
  cmp -s "$f" "$hooks/${f##*/}" 2>/dev/null || mv -f "$f" "$hooks/${f##*/}"
done
rm -rf "$snap"
exit $status