torture: Extract testid.txt generation to separate script

The kvm.sh script places a testid.txt file in the top-level results
directory in order to identify the tree and commit that was tested.
This works well, but there are scripts other than kvm.sh that also create
results directories, and it would be good for them to also identify
exactly what was tested.

This commit therefore extracts the testid.txt generation to a new
mktestid.sh script so that it can be easily used elsewhere.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.upadhyay@kernel.org>

Author: paulmckrcu

tools/testing/selftests/rcutorture/bin/kvm.sh

@@ -442,18 +442,7 @@ echo $scriptname $args
 touch $resdir/$ds/log
 echo $scriptname $args >> $resdir/$ds/log
 echo ${TORTURE_SUITE} > $resdir/$ds/torture_suite
-echo Build directory: `pwd` > $resdir/$ds/testid.txt
-if test -d .git
-then
-	echo Current commit: `git rev-parse HEAD` >> $resdir/$ds/testid.txt
-	echo >> $resdir/$ds/testid.txt
-	echo ' ---' Output of "'"git status"'": >> $resdir/$ds/testid.txt
-	git status >> $resdir/$ds/testid.txt
-	echo >> $resdir/$ds/testid.txt
-	echo >> $resdir/$ds/testid.txt
-	echo ' ---' Output of "'"git diff HEAD"'": >> $resdir/$ds/testid.txt
-	git diff HEAD >> $resdir/$ds/testid.txt
-fi
+mktestid.sh $resdir/$ds
 ___EOF___
 kvm-assign-cpus.sh /sys/devices/system/node > $T/cpuarray.awk
 kvm-get-cpus-script.sh $T/cpuarray.awk $T/dumpbatches.awk

tools/testing/selftests/rcutorture/bin/mktestid.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Create a testid.txt file in the specified directory.
+#
+# Usage: mktestid.sh dirpath
+#
+# Copyright (C) Meta Platforms, Inc.  2025
+#
+# Author: Paul E. McKenney <paulmck@kernel.org>
+
+resdir="$1"
+if test -z "${resdir}" || ! test -d "${resdir}" || ! test -w "${resdir}"
+then
+	echo Path '"'${resdir}'"' not writeable directory, no ${resdir}/testid.txt.
+	exit 1
+fi
+echo Build directory: `pwd` > ${resdir}/testid.txt
+if test -d .git
+then
+	echo Current commit: `git rev-parse HEAD` >> ${resdir}/testid.txt
+	echo >> ${resdir}/testid.txt
+	echo ' ---' Output of "'"git status"'": >> ${resdir}/testid.txt
+	git status >> ${resdir}/testid.txt
+	echo >> ${resdir}/testid.txt
+	echo >> ${resdir}/testid.txt
+	echo ' ---' Output of "'"git diff HEAD"'": >> ${resdir}/testid.txt
+	git diff HEAD >> ${resdir}/testid.txt
+fi