cocci: Start a vcocci.sh convenience script

It doesn't do half of the things I have in mind, but it's good enough
as a starting point to remove error-prone manual copy-pasta of commands
from the README.

Eventually it should also become usable for out-of-tree code.

tools/coccinelle/README.rst

 ..
-	Copyright (c) 2019-2021 Varnish Software AS
+	Copyright (c) 2019-2022 Varnish Software AS
 	SPDX-License-Identifier: BSD-2-Clause
 	See LICENSE file for full text of license
 
@@ -9,6 +9,8 @@ maintenance.
 Each patch should, in a comment section, explain its purpose. They may be fit
 for both the in-tree code style or out-of-tree VMOD and VUT development.
 
+For in-tree usage, see the ``vcocci.sh`` script for convenience.
+
 Unless noted otherwise, all patches should work when invoked as::
 
 	spatch --macro-file tools/coccinelle/vdef.h \

tools/coccinelle/vcocci.sh

+#!/bin/sh
+#
+# Copyright (c) 2022 Varnish Software AS
+# All rights reserved.
+#
+# Author: Dridi Boukelmoune <dridi.boukelmoune@gmail.com>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+set -e
+set -u
+
+readonly SCRIPT=$(basename $0)
+readonly TMP=$(mktemp -d)
+trap 'rm -rf $TMP' EXIT
+
+usage() {
+	ERR=${1:-1}
+	test $ERR == 0 ||
+	exec >&2
+
+	cat <<-EOF
+	Usage: $SCRIPT <command> [...]
+	       $SCRIPT help
+
+	Operate Coccinnelle semantic patches.
+
+	Available commands:
+
+	    apply <file>    Apply a patch to the source tree
+	    parse <file>    Parse and expand a patch
+	    mkiso           Generate a varnish.iso file
+	    help            Show this help and exit
+
+	This script operates directly on the Varnish Cache git repository.
+	EOF
+	exit $ERR
+}
+
+errorf() {
+	printf >&2 'Error: '
+	printf >&2 "$@"
+	printf >&2 '\n'
+}
+
+exec_spatch() {
+	exec spatch \
+		--macro-file "$SRCDIR/tools/coccinelle/vdef.h" \
+		-I "$SRCDIR/include/" \
+		-I "$SRCDIR/bin/varnishd/" \
+		"$@"
+}
+
+cmd_apply() {
+	if test $# != 1
+	then
+		errorf 'invalid arguments'
+		usage
+	fi
+	exec_spatch --in-place --dir "$SRCDIR" --sp-file "$1"
+}
+
+cmd_parse() {
+	if test $# != 1
+	then
+		errorf 'invalid arguments'
+		usage
+	fi
+	exec_spatch --parse-cocci --sp-file "$1"
+}
+
+cmd_mkiso() {
+	errorf 'not implemented'
+	exit 1
+}
+
+git rev-parse --show-toplevel >/dev/null ||
+usage
+
+if test $# = 0
+then
+	errorf 'missing command'
+	usage
+fi
+
+readonly SRCDIR=$(git rev-parse --show-toplevel)
+
+CMD=$1
+shift
+
+case $CMD in
+	apply)
+		cmd_apply "$@"
+		;;
+	parse)
+		cmd_parse "$@"
+		;;
+	mkiso)
+		cmd_mkiso "$@"
+		;;
+	help)
+		usage 0
+		;;
+	*)
+		errorf "unknown command '%s'" "$CMD"
+		usage
+		;;
+esac