rcutorture: Note diffs from git commits

The current scripting only keeps track of the git SHA-1 of the current
HEAD.  This can cause confusion in cases where testing ran in a git
tree where changes had not yet been checked in.  This commit therefore
also records the output of "git diff HEAD" to provide the information
needed to reconstruct the source tree that was tested.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

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

@@ -276,6 +276,10 @@ if test -d .git
 then
 	git status >> $resdir/$ds/testid.txt
 	git rev-parse HEAD >> $resdir/$ds/testid.txt
+	if ! git diff HEAD > $T/git-diff 2>&1
+	then
+		cp $T/git-diff $resdir/$ds
+	fi
 fi
 ___EOF___
 awk < $T/cfgcpu.pack \