[PATCH] diff: align move detection error handling with other options

[Stefan Beller <sbeller@google.com>]

This changes the error handling for the options --color-moved-ws
and --color-moved-ws to be like the rest of the options.

Move the die() call out of parse_color_moved_ws into the parsing
of command line options. As the function returns a bit field, change
its signature to return an unsigned instead of an int; add a new bit
to signal errors. Once the error is signaled, we discard the other
bits, such that it doesn't matter if the error bit overlaps with any
other bit.

Signed-off-by: Stefan Beller <sbeller@google.com>
---

c.f.
./git -c diff.colormovedws=bogus diff HEAD
error: unknown color-moved-ws mode 'bogus'
fatal: unable to parse 'diff.colormovedws' from command-line config
./git -c core.abbrev=41 diff
error: abbrev length out of range: 41
fatal: unable to parse 'core.abbrev' from command-line config

./git diff --color=bogus
error: option `color' expects "always", "auto", or "never"
./git -c diff.colormovedws=bogus diff HEAD
error: unknown color-moved-ws mode 'bogus'
fatal: unable to parse 'diff.colormovedws' from command-line config


 diff.c                     | 25 ++++++++++++++++---------
 diff.h                     |  3 ++-
 t/t4015-diff-whitespace.sh | 18 ++++++++++++++++++
 3 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/diff.c b/diff.c
index 8647db3d30..d7d467b605 100644
--- a/diff.c
+++ b/diff.c
@@ -291,7 +291,7 @@ static int parse_color_moved(const char *arg)
 		return error(_("color moved setting must be one of 'no', 'default', 'blocks', 'zebra', 'dimmed-zebra', 'plain'"));
 }
 
-static int parse_color_moved_ws(const char *arg)
+static unsigned parse_color_moved_ws(const char *arg)
 {
 	int ret = 0;
 	struct string_list l = STRING_LIST_INIT_DUP;
@@ -312,15 +312,19 @@ static int parse_color_moved_ws(const char *arg)
 			ret |= XDF_IGNORE_WHITESPACE;
 		else if (!strcmp(sb.buf, "allow-indentation-change"))
 			ret |= COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE;
-		else
-			error(_("ignoring unknown color-moved-ws mode '%s'"), sb.buf);
+		else {
+			ret |= COLOR_MOVED_WS_ERROR;
+			error(_("unknown color-moved-ws mode '%s', possible values are 'ignore-space-change', 'ignore-space-at-eol', 'ignore-all-space', 'allow-indentation-change'"), sb.buf);
+		}
 
 		strbuf_release(&sb);
 	}
 
 	if ((ret & COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE) &&
-	    (ret & XDF_WHITESPACE_FLAGS))
-		die(_("color-moved-ws: allow-indentation-change cannot be combined with other white space modes"));
+	    (ret & XDF_WHITESPACE_FLAGS)) {
+		error(_("color-moved-ws: allow-indentation-change cannot be combined with other white space modes"));
+		ret |= COLOR_MOVED_WS_ERROR;
+	}
 
 	string_list_clear(&l, 0);
 
@@ -341,8 +345,8 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 	if (!strcmp(var, "diff.colormovedws")) {
-		int cm = parse_color_moved_ws(value);
-		if (cm < 0)
+		unsigned cm = parse_color_moved_ws(value);
+		if (cm & COLOR_MOVED_WS_ERROR)
 			return -1;
 		diff_color_moved_ws_default = cm;
 		return 0;
@@ -5032,10 +5036,13 @@ int diff_opt_parse(struct diff_options *options,
 	else if (skip_prefix(arg, "--color-moved=", &arg)) {
 		int cm = parse_color_moved(arg);
 		if (cm < 0)
-			die("bad --color-moved argument: %s", arg);
+			return error("bad --color-moved argument: %s", arg);
 		options->color_moved = cm;
 	} else if (skip_prefix(arg, "--color-moved-ws=", &arg)) {
-		options->color_moved_ws_handling = parse_color_moved_ws(arg);
+		unsigned cm = parse_color_moved_ws(arg);
+		if (cm & COLOR_MOVED_WS_ERROR)
+			return -1;
+		options->color_moved_ws_handling = cm;
 	} else if (skip_to_optional_arg_default(arg, "--color-words", &options->word_regex, NULL)) {
 		options->use_color = 1;
 		options->word_diff = DIFF_WORDS_COLOR;
diff --git a/diff.h b/diff.h
index ce5e8a8183..9e8061ca29 100644
--- a/diff.h
+++ b/diff.h
@@ -225,7 +225,8 @@ struct diff_options {
 
 	/* XDF_WHITESPACE_FLAGS regarding block detection are set at 2, 3, 4 */
 	#define COLOR_MOVED_WS_ALLOW_INDENTATION_CHANGE (1<<5)
-	int color_moved_ws_handling;
+	#define COLOR_MOVED_WS_ERROR (1<<0)
+	unsigned color_moved_ws_handling;
 
 	struct repository *repo;
 };
diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index a9fb226c5a..9a3e4fdfec 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -1890,6 +1890,24 @@ test_expect_success 'compare whitespace delta across moved blocks' '
 	test_cmp expected actual
 '
 
+test_expect_success 'bogus settings in move detection erroring out' '
+	test_must_fail git diff --color-moved=bogus 2>err &&
+	test_i18ngrep "must be one of" err &&
+	test_i18ngrep bogus err &&
+
+	test_must_fail git -c diff.colormoved=bogus diff 2>err &&
+	test_i18ngrep "must be one of" err &&
+	test_i18ngrep "from command-line config" err &&
+
+	test_must_fail git diff --color-moved-ws=bogus 2>err &&
+	test_i18ngrep "possible values" err &&
+	test_i18ngrep bogus err &&
+
+	test_must_fail git -c diff.colormovedws=bogus diff 2>err &&
+	test_i18ngrep "possible values" err &&
+	test_i18ngrep "from command-line config" err
+'
+
 test_expect_success 'compare whitespace delta incompatible with other space options' '
 	test_must_fail git diff \
 		--color-moved-ws=allow-indentation-change,ignore-all-space \
-- 
2.19.1.1215.g8438c0b245-goog