port hook template to bash

this avoids some version-specific code in python

this also makes the bootstrap script slightly more portable

pre_commit/resources/hook-tmpl

@@ -1,44 +1,20 @@
-#!/usr/bin/env python3
+#!/usr/bin/env bash
 # File generated by pre-commit: https://pre-commit.com
 # ID: 138fd403232d2ddd5efb44317e38bf03
-import os
-import sys
-
-# we try our best, but the shebang of this script is difficult to determine:
-# - macos doesn't ship with python3
-# - windows executables are almost always `python.exe`
-# therefore we continue to support python2 for this small script
-if sys.version_info < (3, 3):
-    from distutils.spawn import find_executable as which
-else:
-    from shutil import which
-
-# work around https://github.com/Homebrew/homebrew-core/issues/30445
-os.environ.pop('__PYVENV_LAUNCHER__', None)
 
 # start templated
-INSTALL_PYTHON = ''
-ARGS = ['hook-impl']
+INSTALL_PYTHON=''
+ARGS=(hook-impl)
 # end templated
-ARGS.extend(('--hook-dir', os.path.realpath(os.path.dirname(__file__))))
-ARGS.append('--')
-ARGS.extend(sys.argv[1:])
 
-DNE = '`pre-commit` not found.  Did you forget to activate your virtualenv?'
-if os.access(INSTALL_PYTHON, os.X_OK):
-    CMD = [INSTALL_PYTHON, '-mpre_commit']
-elif which('pre-commit'):
-    CMD = ['pre-commit']
-else:
-    raise SystemExit(DNE)
+HERE="$(cd "$(dirname "$0")" && pwd)"
+ARGS+=(--hook-dir "$HERE" -- "$@")
 
-CMD.extend(ARGS)
-if sys.platform == 'win32':  # https://bugs.python.org/issue19124
-    import subprocess
-
-    if sys.version_info < (3, 7):  # https://bugs.python.org/issue25942
-        raise SystemExit(subprocess.Popen(CMD).wait())
-    else:
-        raise SystemExit(subprocess.call(CMD))
-else:
-    os.execvp(CMD[0], CMD)
+if [ -x "$INSTALL_PYTHON" ]; then
+    exec "$INSTALL_PYTHON" -mpre_commit "${ARGS[@]}"
+elif command -v pre-commit; then
+    exec pre-commit "${ARGS[@]}"
+else
+   echo '`pre-commit` not found.  Did you forget to activate your virtualenv?' 1>&2
+   exit 1
+fi