checkpatch: change format of --color argument to --color[=WHEN]

The boolean --color argument did not offer the ability to force
colourized output even if stdout is not a terminal.  Change the format
of the argument to the familiar --color[=WHEN] construct as seen in
common Linux utilities such as git, ls and dmesg, which allows the user
to specify whether to colourize output "always", "never", or "auto" when
the output is a terminal.  The default is "auto".

The old command-line uses of --color and --no-color are unchanged.

Link: http://lkml.kernel.org/r/efe43bdbad400f39ba691ae663044462493b0773.1496799721.git.joe@perches.com
Signed-off-by: John Brooks <john@fastquake.com>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

scripts/checkpatch.pl

@@ -57,7 +57,7 @@ my $codespell = 0;
 my $codespellfile = "/usr/share/codespell/dictionary.txt";
 my $conststructsfile = "$D/const_structs.checkpatch";
 my $typedefsfile = "";
-my $color = 1;
+my $color = "auto";
 my $allow_c99_comments = 1;
 
 sub help {
@@ -116,7 +116,8 @@ Options:
                              (default:/usr/share/codespell/dictionary.txt)
   --codespellfile            Use this codespell dictionary
   --typedefsfile             Read additional types from this file
-  --color                    Use colors when output is STDOUT (default: on)
+  --color[=WHEN]             Use colors 'always', 'never', or only when output
+                             is a terminal ('auto'). Default is 'auto'.
   -h, --help, --version      display this help and exit
 
 When FILE is - read standard input.
@@ -182,6 +183,14 @@ if (-f $conf) {
 	unshift(@ARGV, @conf_args) if @conf_args;
 }
 
+# Perl's Getopt::Long allows options to take optional arguments after a space.
+# Prevent --color by itself from consuming other arguments
+foreach (@ARGV) {
+	if ($_ eq "--color" || $_ eq "-color") {
+		$_ = "--color=$color";
+	}
+}
+
 GetOptions(
 	'q|quiet+'	=> \$quiet,
 	'tree!'		=> \$tree,
@@ -212,7 +221,9 @@ GetOptions(
 	'codespell!'	=> \$codespell,
 	'codespellfile=s'	=> \$codespellfile,
 	'typedefsfile=s'	=> \$typedefsfile,
-	'color!'	=> \$color,
+	'color=s'	=> \$color,
+	'no-color'	=> \$color,	#keep old behaviors of -nocolor
+	'nocolor'	=> \$color,	#keep old behaviors of -nocolor
 	'h|help'	=> \$help,
 	'version'	=> \$help
 ) or help(1);
@@ -238,6 +249,18 @@ if ($#ARGV < 0) {
 	push(@ARGV, '-');
 }
 
+if ($color =~ /^[01]$/) {
+	$color = !$color;
+} elsif ($color =~ /^always$/i) {
+	$color = 1;
+} elsif ($color =~ /^never$/i) {
+	$color = 0;
+} elsif ($color =~ /^auto$/i) {
+	$color = (-t STDOUT);
+} else {
+	die "Invalid color mode: $color\n";
+}
+
 sub hash_save_array_words {
 	my ($hashRef, $arrayRef) = @_;
 
@@ -1883,7 +1906,7 @@ sub report {
 		return 0;
 	}
 	my $output = '';
-	if (-t STDOUT && $color) {
+	if ($color) {
 		if ($level eq 'ERROR') {
 			$output .= RED;
 		} elsif ($level eq 'WARNING') {
@@ -1894,10 +1917,10 @@ sub report {
 	}
 	$output .= $prefix . $level . ':';
 	if ($show_types) {
-		$output .= BLUE if (-t STDOUT && $color);
+		$output .= BLUE if ($color);
 		$output .= "$type:";
 	}
-	$output .= RESET if (-t STDOUT && $color);
+	$output .= RESET if ($color);
 	$output .= ' ' . $msg . "\n";
 
 	if ($showfile) {