tools/bootconfig: Add testcases for value override operator

Add some testcases and examples for value override operator.

Link: https://lkml.kernel.org/r/159482883824.126704.2166030493721357163.stgit@devnote2

Signed-off-by: Masami Hiramatsu <[e-mail]>
Signed-off-by: Steven Rostedt (VMware) <[e-mail]>

tools/bootconfig/samples/bad-override.bconf

···
+key.subkey = value
+# We can not override pre-defined subkeys with value
+key := value

tools/bootconfig/samples/bad-override2.bconf

···
+key = value
+# We can not override pre-defined value with subkey
+key.subkey := value

tools/bootconfig/samples/good-override.bconf

···
+# Override the value
+key.word = 1,2,4
+key.word := 2,3
+
+# No pre-defined key
+key.new.word := "new"

tools/bootconfig/test-bootconfig.sh

···
 xpass grep -q "baz" $OUTFILE
 xpass grep -q "qux" $OUTFILE
 
+echo "Override same-key values"
+cat > $TEMPCONF << EOF
+key = bar, baz
+key := qux
+EOF
+echo > $INITRD
+
+xpass $BOOTCONF -a $TEMPCONF $INITRD
+$BOOTCONF $INITRD > $OUTFILE
+xfail grep -q "bar" $OUTFILE
+xfail grep -q "baz" $OUTFILE
+xpass grep -q "qux" $OUTFILE
+
 echo "Double/single quotes test"
 echo "key = '\"string\"';" > $TEMPCONF
 $BOOTCONF -a $TEMPCONF $INITRD