diff: allow --no-color-moved-ws

Allow --no-color-moved-ws and --color-moved-ws=no to cancel any previous
--color-moved-ws option.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/diff-options.txt

@@ -306,6 +306,8 @@ endif::git-diff[]
 	These modes can be given as a comma separated list:
 +
 --
+no::
+	Do not ignore whitespace when performing move detection.
 ignore-space-at-eol::
 	Ignore changes in whitespace at EOL.
 ignore-space-change::
@@ -322,6 +324,11 @@ allow-indentation-change::
 	other modes.
 --
 
+--no-color-moved-ws::
+	Do not ignore whitespace when performing move detection. This can be
+	used to override configuration settings. It is the same as
+	`--color-moved-ws=no`.
+
 --word-diff[=<mode>]::
 	Show a word diff, using the <mode> to delimit changed words.
 	By default, words are delimited by whitespace; see

diff.c

@@ -304,7 +304,9 @@ static int parse_color_moved_ws(const char *arg)
 		strbuf_addstr(&sb, i->string);
 		strbuf_trim(&sb);
 
-		if (!strcmp(sb.buf, "ignore-space-change"))
+		if (!strcmp(sb.buf, "no"))
+			ret = 0;
+		else if (!strcmp(sb.buf, "ignore-space-change"))
 			ret |= XDF_IGNORE_WHITESPACE_CHANGE;
 		else if (!strcmp(sb.buf, "ignore-space-at-eol"))
 			ret |= XDF_IGNORE_WHITESPACE_AT_EOL;
@@ -5036,6 +5038,8 @@ int diff_opt_parse(struct diff_options *options,
 		if (cm < 0)
 			die("bad --color-moved argument: %s", arg);
 		options->color_moved = cm;
+	} else if (!strcmp(arg, "--no-color-moved-ws")) {
+		options->color_moved_ws_handling = 0;
 	} else if (skip_prefix(arg, "--color-moved-ws=", &arg)) {
 		options->color_moved_ws_handling = parse_color_moved_ws(arg);
 	} else if (skip_to_optional_arg_default(arg, "--color-words", &options->word_regex, NULL)) {