scripts/dtc: dtx_diff - add color output support

Add new -c/--color options, to enhance the diff output with color, and
improve the user's experience.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Frank Rowand <frank.rowand@sony.com>
Tested-by: Frank Rowand <frank.rowand@sony.com>
Signed-off-by: Rob Herring <robh@kernel.org>

scripts/dtc/dtx_diff

@@ -20,6 +20,8 @@ Usage:
 
 
       --annotate    synonym for -T
+      --color       synonym for -c (requires diff with --color support)
+       -c           enable colored output
        -f           print full dts in diff (--unified=99999)
        -h           synonym for --help
        -help        synonym for --help
@@ -177,6 +179,7 @@ compile_to_dts() {
 annotate=""
 cmd_diff=0
 diff_flags="-u"
+diff_color=""
 dtx_file_1=""
 dtx_file_2=""
 dtc_sort="-s"
@@ -188,6 +191,13 @@ while [ $# -gt 0 ] ; do
 
 	case $1 in
 
+	-c | --color )
+		if diff --color /dev/null /dev/null 2>/dev/null ; then
+			diff_color="--color=always"
+		fi
+		shift
+		;;
+
 	-f )
 		diff_flags="--unified=999999"
 		shift
@@ -343,7 +353,7 @@ DTC="\
 
 if (( ${cmd_diff} )) ; then
 
-	diff ${diff_flags} --label "${dtx_file_1}" --label "${dtx_file_2}" \
+	diff ${diff_flags} ${diff_color} --label "${dtx_file_1}" --label "${dtx_file_2}" \
 		<(compile_to_dts "${dtx_file_1}" "${dtx_path_1_dtc_include}") \
 		<(compile_to_dts "${dtx_file_2}" "${dtx_path_2_dtc_include}")