Merge branch 'wc/diff'

* wc/diff:
  Test interaction between diff --check and --exit-code
  Use shorter error messages for whitespace problems
  Add tests for "git diff --check" with core.whitespace options
  Make "diff --check" output match "git apply"
  Unify whitespace checking
  diff --check: minor fixups
  "diff --check" should affect exit status

12 files changed, 396 insertions, 192 deletions

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 5d22b7b58..9ecc1d7bc 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -93,7 +93,9 @@ endif::git-format-patch[]
 
 --check::
 	Warn if changes introduce trailing whitespace
-	or an indent that uses a space before a tab.
+	or an indent that uses a space before a tab. Exits with
+	non-zero status if problems are found. Not compatible with
+	--exit-code.
 
 --full-index::
 	Instead of the first handful characters, show full
diff --git a/builtin-apply.c b/builtin-apply.c
index f2e9a332c..2edd83bf4 100644
--- a/builtin-apply.c
+++ b/builtin-apply.c
@@ -900,56 +900,22 @@ static int find_header(char *line, unsigned long size, int *hdrsize, struct patc
 
 static void check_whitespace(const char *line, int len, unsigned ws_rule)
 {
-	const char *err = "Adds trailing whitespace";
-	int seen_space = 0;
-	int i;
-
-	/*
-	 * We know len is at least two, since we have a '+' and we
-	 * checked that the last character was a '\n' before calling
-	 * this function.  That is, an addition of an empty line would
-	 * check the '+' here.  Sneaky...
-	 */
-	if ((ws_rule & WS_TRAILING_SPACE) && isspace(line[len-2]))
-		goto error;
-
-	/*
-	 * Make sure that there is no space followed by a tab in
-	 * indentation.
-	 */
-	if (ws_rule & WS_SPACE_BEFORE_TAB) {
-		err = "Space in indent is followed by a tab";
-		for (i = 1; i < len; i++) {
-			if (line[i] == '\t') {
-				if (seen_space)
-					goto error;
-			}
-			else if (line[i] == ' ')
-				seen_space = 1;
-			else
-				break;
-		}
-	}
-
-	/*
-	 * Make sure that the indentation does not contain more than
-	 * 8 spaces.
-	 */
-	if ((ws_rule & WS_INDENT_WITH_NON_TAB) &&
-	    (8 < len) && !strncmp("+        ", line, 9)) {
-		err = "Indent more than 8 places with spaces";
-		goto error;
-	}
-	return;
+	char *err;
+	unsigned result = check_and_emit_line(line + 1, len - 1, ws_rule,
+	    NULL, NULL, NULL, NULL);
+	if (!result)
+		return;
 
- error:
 	whitespace_error++;
 	if (squelch_whitespace_errors &&
 	    squelch_whitespace_errors < whitespace_error)
 		;
-	else
-		fprintf(stderr, "%s.\n%s:%d:%.*s\n",
-			err, patch_input_file, linenr, len-2, line+1);
+	else {
+		err = whitespace_error_string(result);
+		fprintf(stderr, "%s:%d: %s.\n%.*s\n",
+		     patch_input_file, linenr, err, len - 2, line + 1);
+		free(err);
+	}
 }
 
 /*
diff --git a/builtin-diff-files.c b/builtin-diff-files.c
index 046b7e34b..9c0411165 100644
--- a/builtin-diff-files.c
+++ b/builtin-diff-files.c
@@ -31,7 +31,5 @@ int cmd_diff_files(int argc, const char **argv, const char *prefix)
 	if (!rev.diffopt.output_format)
 		rev.diffopt.output_format = DIFF_FORMAT_RAW;
 	result = run_diff_files_cmd(&rev, argc, argv);
-	if (DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
-		return DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0;
-	return result;
+	return diff_result_code(&rev.diffopt, result);
 }
diff --git a/builtin-diff-index.c b/builtin-diff-index.c
index 556c506bf..0f2390a20 100644
--- a/builtin-diff-index.c
+++ b/builtin-diff-index.c
@@ -44,7 +44,5 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 		return -1;
 	}
 	result = run_diff_index(&rev, cached);
-	if (DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
-		return DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0;
-	return result;
+	return diff_result_code(&rev.diffopt, result);
 }
diff --git a/builtin-diff-tree.c b/builtin-diff-tree.c
index 2e13716ee..ebc50efbd 100644
--- a/builtin-diff-tree.c
+++ b/builtin-diff-tree.c
@@ -117,23 +117,21 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
 		break;
 	}
 
-	if (!read_stdin)
-		return DIFF_OPT_TST(&opt->diffopt, EXIT_WITH_STATUS)
-			&& DIFF_OPT_TST(&opt->diffopt, HAS_CHANGES);
+	if (read_stdin) {
+		if (opt->diffopt.detect_rename)
+			opt->diffopt.setup |= (DIFF_SETUP_USE_SIZE_CACHE |
+					       DIFF_SETUP_USE_CACHE);
+		while (fgets(line, sizeof(line), stdin)) {
+			unsigned char sha1[20];
 
-	if (opt->diffopt.detect_rename)
-		opt->diffopt.setup |= (DIFF_SETUP_USE_SIZE_CACHE |
-				       DIFF_SETUP_USE_CACHE);
-	while (fgets(line, sizeof(line), stdin)) {
-		unsigned char sha1[20];
-
-		if (get_sha1_hex(line, sha1)) {
-			fputs(line, stdout);
-			fflush(stdout);
+			if (get_sha1_hex(line, sha1)) {
+				fputs(line, stdout);
+				fflush(stdout);
+			}
+			else
+				diff_tree_stdin(line);
 		}
-		else
-			diff_tree_stdin(line);
 	}
-	return DIFF_OPT_TST(&opt->diffopt, EXIT_WITH_STATUS)
-		&& DIFF_OPT_TST(&opt->diffopt, HAS_CHANGES);
+
+	return diff_result_code(&opt->diffopt, 0);
 }
diff --git a/builtin-diff.c b/builtin-diff.c
index 55fb84c73..29365a0b1 100644
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -244,7 +244,8 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	DIFF_OPT_SET(&rev.diffopt, ALLOW_EXTERNAL);
 	DIFF_OPT_SET(&rev.diffopt, RECURSIVE);
 
-	/* If the user asked for our exit code then don't start a
+	/*
+	 * If the user asked for our exit code then don't start a
 	 * pager or we would end up reporting its exit code instead.
 	 */
 	if (!DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
@@ -351,9 +352,7 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	else
 		result = builtin_diff_combined(&rev, argc, argv,
 					     ent, ents);
-	if (DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
-		result = DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0;
-
+	result = diff_result_code(&rev.diffopt, result);
 	if (1 < rev.diffopt.skip_stat_unmatch)
 		refresh_index_quietly();
 	return result;
diff --git a/cache.h b/cache.h
index 27d90fe54..39331c28b 100644
--- a/cache.h
+++ b/cache.h
@@ -655,6 +655,10 @@ void shift_tree(const unsigned char *, const unsigned char *, unsigned char *, i
 extern unsigned whitespace_rule_cfg;
 extern unsigned whitespace_rule(const char *);
 extern unsigned parse_whitespace_rule(const char *);
+extern unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
+    FILE *stream, const char *set,
+    const char *reset, const char *ws);
+extern char *whitespace_error_string(unsigned ws);
 
 /* ls-files */
 int pathspec_match(const char **spec, char *matched, const char *filename, int skiplen);
diff --git a/diff.c b/diff.c
index 3dd2f35f7..08ec66c79 100644
--- a/diff.c
+++ b/diff.c
@@ -486,88 +486,9 @@ const char *diff_get_color(int diff_use_color, enum color_diff ix)
 
 static void emit_line(const char *set, const char *reset, const char *line, int len)
 {
-	if (len > 0 && line[len-1] == '\n')
-		len--;
 	fputs(set, stdout);
 	fwrite(line, len, 1, stdout);
-	puts(reset);
-}
-
-static void emit_line_with_ws(int nparents,
-			      const char *set, const char *reset, const char *ws,
-			      const char *line, int len, unsigned ws_rule)
-{
-	int col0 = nparents;
-	int last_tab_in_indent = -1;
-	int last_space_in_indent = -1;
-	int i;
-	int tail = len;
-	int need_highlight_leading_space = 0;
-	/*
-	 * The line is a newly added line.  Does it have funny leading
-	 * whitespaces?  In indent, SP should never precede a TAB.  In
-	 * addition, under "indent with non tab" rule, there should not
-	 * be more than 8 consecutive spaces.
-	 */
-	for (i = col0; i < len; i++) {
-		if (line[i] == '\t') {
-			last_tab_in_indent = i;
-			if ((ws_rule & WS_SPACE_BEFORE_TAB) &&
-			    0 <= last_space_in_indent)
-				need_highlight_leading_space = 1;
-		}
-		else if (line[i] == ' ')
-			last_space_in_indent = i;
-		else
-			break;
-	}
-	if ((ws_rule & WS_INDENT_WITH_NON_TAB) &&
-	    0 <= last_space_in_indent &&
-	    last_tab_in_indent < 0 &&
-	    8 <= (i - col0)) {
-		last_tab_in_indent = i;
-		need_highlight_leading_space = 1;
-	}
-	fputs(set, stdout);
-	fwrite(line, col0, 1, stdout);
 	fputs(reset, stdout);
-	if (((i == len) || line[i] == '\n') && i != col0) {
-		/* The whole line was indent */
-		emit_line(ws, reset, line + col0, len - col0);
-		return;
-	}
-	i = col0;
-	if (need_highlight_leading_space) {
-		while (i < last_tab_in_indent) {
-			if (line[i] == ' ') {
-				fputs(ws, stdout);
-				putchar(' ');
-				fputs(reset, stdout);
-			}
-			else
-				putchar(line[i]);
-			i++;
-		}
-	}
-	tail = len - 1;
-	if (line[tail] == '\n' && i < tail)
-		tail--;
-	if (ws_rule & WS_TRAILING_SPACE) {
-		while (i < tail) {
-			if (!isspace(line[tail]))
-				break;
-			tail--;
-		}
-	}
-	if ((i < tail && line[tail + 1] != '\n')) {
-		/* This has whitespace between tail+1..len */
-		fputs(set, stdout);
-		fwrite(line + i, tail - i + 1, 1, stdout);
-		fputs(reset, stdout);
-		emit_line(ws, reset, line + tail + 1, len - tail - 1);
-	}
-	else
-		emit_line(set, reset, line + i, len - i);
 }
 
 static void emit_add_line(const char *reset, struct emit_callback *ecbdata, const char *line, int len)
@@ -577,9 +498,13 @@ static void emit_add_line(const char *reset, struct emit_callback *ecbdata, cons
 
 	if (!*ws)
 		emit_line(set, reset, line, len);
-	else
-		emit_line_with_ws(ecbdata->nparents, set, reset, ws,
-				  line, len, ecbdata->ws_rule);
+	else {
+		/* Emit just the prefix, then the rest. */
+		emit_line(set, reset, line, ecbdata->nparents);
+		(void)check_and_emit_line(line + ecbdata->nparents,
+		    len - ecbdata->nparents, ecbdata->ws_rule,
+		    stdout, set, reset, ws);
+	}
 }
 
 static void fn_out_consume(void *priv, char *line, unsigned long len)
@@ -1031,6 +956,7 @@ struct checkdiff_t {
 	const char *filename;
 	int lineno, color_diff;
 	unsigned ws_rule;
+	unsigned status;
 };
 
 static void checkdiff_consume(void *priv, char *line, unsigned long len)
@@ -1039,44 +965,19 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
 	const char *ws = diff_get_color(data->color_diff, DIFF_WHITESPACE);
 	const char *reset = diff_get_color(data->color_diff, DIFF_RESET);
 	const char *set = diff_get_color(data->color_diff, DIFF_FILE_NEW);
+	char *err;
 
 	if (line[0] == '+') {
-		int i, spaces = 0, space_before_tab = 0, white_space_at_end = 0;
-
-		/* check space before tab */
-		for (i = 1; i < len; i++) {
-			if (line[i] == ' ')
-				spaces++;
-			else if (line[i] == '\t') {
-				if (spaces) {
-					space_before_tab = 1;
-					break;
-				}
-			}
-			else
-				break;
-		}
-
-		/* check whitespace at line end */
-		if (line[len - 1] == '\n')
-			len--;
-		if (isspace(line[len - 1]))
-			white_space_at_end = 1;
-
-		if (space_before_tab || white_space_at_end) {
-			printf("%s:%d: %s", data->filename, data->lineno, ws);
-			if (space_before_tab) {
-				printf("space before tab");
-				if (white_space_at_end)
-					putchar(',');
-			}
-			if (white_space_at_end)
-				printf("whitespace at end");
-			printf(":%s ", reset);
-			emit_line_with_ws(1, set, reset, ws, line, len,
-					  data->ws_rule);
-		}
-
+		data->status = check_and_emit_line(line + 1, len - 1,
+		    data->ws_rule, NULL, NULL, NULL, NULL);
+		if (!data->status)
+			return;
+		err = whitespace_error_string(data->status);
+		printf("%s:%d: %s.\n", data->filename, data->lineno, err);
+		free(err);
+		emit_line(set, reset, line, 1);
+		(void)check_and_emit_line(line + 1, len - 1, data->ws_rule,
+		    stdout, set, reset, ws);
 		data->lineno++;
 	} else if (line[0] == ' ')
 		data->lineno++;
@@ -1491,6 +1392,8 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
  free_and_return:
 	diff_free_filespec_data(one);
 	diff_free_filespec_data(two);
+	if (data.status)
+		DIFF_OPT_SET(o, CHECK_FAILED);
 }
 
 struct diff_filespec *alloc_filespec(const char *path)
@@ -3171,6 +3074,20 @@ void diffcore_std(struct diff_options *options)
 		DIFF_OPT_CLR(options, HAS_CHANGES);
 }
 
+int diff_result_code(struct diff_options *opt, int status)
+{
+	int result = 0;
+	if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
+	    !(opt->output_format & DIFF_FORMAT_CHECKDIFF))
+		return status;
+	if (DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
+	    DIFF_OPT_TST(opt, HAS_CHANGES))
+		result |= 01;
+	if ((opt->output_format & DIFF_FORMAT_CHECKDIFF) &&
+	    DIFF_OPT_TST(opt, CHECK_FAILED))
+		result |= 02;
+	return result;
+}
 
 void diff_addremove(struct diff_options *options,
 		    int addremove, unsigned mode,
diff --git a/diff.h b/diff.h
index a52496a10..7e8000a5d 100644
--- a/diff.h
+++ b/diff.h
@@ -59,6 +59,7 @@ typedef void (*diff_format_fn_t)(struct diff_queue_struct *q,
 #define DIFF_OPT_ALLOW_EXTERNAL      (1 << 13)
 #define DIFF_OPT_EXIT_WITH_STATUS    (1 << 14)
 #define DIFF_OPT_REVERSE_DIFF        (1 << 15)
+#define DIFF_OPT_CHECK_FAILED        (1 << 16)
 #define DIFF_OPT_TST(opts, flag)    ((opts)->flags & DIFF_OPT_##flag)
 #define DIFF_OPT_SET(opts, flag)    ((opts)->flags |= DIFF_OPT_##flag)
 #define DIFF_OPT_CLR(opts, flag)    ((opts)->flags &= ~DIFF_OPT_##flag)
@@ -246,4 +247,6 @@ extern int run_diff_index(struct rev_info *revs, int cached);
 extern int do_diff_cache(const unsigned char *, struct diff_options *);
 extern int diff_flush_patch_id(struct diff_options *, unsigned char *);
 
+extern int diff_result_code(struct diff_options *, int);
+
 #endif /* DIFF_H */
diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 6adf9d11d..9bff8f5e4 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -117,12 +117,197 @@ EOF
 git diff -b > out
 test_expect_success 'another test, with -b' 'git diff expect out'
 
-
 test_expect_success 'check mixed spaces and tabs in indent' '
 
 	# This is indented with SP HT SP.
 	echo " 	 foo();" > x &&
-	git diff --check | grep "space before tab"
+	git diff --check | grep "space before tab in indent"
+
+'
+
+test_expect_success 'check with no whitespace errors' '
+
+	git commit -m "snapshot" &&
+	echo "foo();" > x &&
+	git diff --check
+
+'
+
+test_expect_success 'check with trailing whitespace' '
+
+	echo "foo(); " > x &&
+	! git diff --check
+
+'
+
+test_expect_success 'check with space before tab in indent' '
+
+	# indent has space followed by hard tab
+	echo " 	foo();" > x &&
+	! git diff --check
+
+'
+
+test_expect_success '--check and --exit-code are not exclusive' '
+
+	git checkout x &&
+	git diff --check --exit-code
+
+'
+
+test_expect_success '--check and --quiet are not exclusive' '
+
+	git diff --check --quiet
+
+'
+
+test_expect_success 'check staged with no whitespace errors' '
+
+	echo "foo();" > x &&
+	git add x &&
+	git diff --cached --check
+
+'
+
+test_expect_success 'check staged with trailing whitespace' '
+
+	echo "foo(); " > x &&
+	git add x &&
+	! git diff --cached --check
+
+'
+
+test_expect_success 'check staged with space before tab in indent' '
+
+	# indent has space followed by hard tab
+	echo " 	foo();" > x &&
+	git add x &&
+	! git diff --cached --check
+
+'
+
+test_expect_success 'check with no whitespace errors (diff-index)' '
+
+	echo "foo();" > x &&
+	git add x &&
+	git diff-index --check HEAD
+
+'
+
+test_expect_success 'check with trailing whitespace (diff-index)' '
+
+	echo "foo(); " > x &&
+	git add x &&
+	! git diff-index --check HEAD
+
+'
+
+test_expect_success 'check with space before tab in indent (diff-index)' '
+
+	# indent has space followed by hard tab
+	echo " 	foo();" > x &&
+	git add x &&
+	! git diff-index --check HEAD
+
+'
+
+test_expect_success 'check staged with no whitespace errors (diff-index)' '
+
+	echo "foo();" > x &&
+	git add x &&
+	git diff-index --cached --check HEAD
+
+'
+
+test_expect_success 'check staged with trailing whitespace (diff-index)' '
+
+	echo "foo(); " > x &&
+	git add x &&
+	! git diff-index --cached --check HEAD
+
+'
+
+test_expect_success 'check staged with space before tab in indent (diff-index)' '
+
+	# indent has space followed by hard tab
+	echo " 	foo();" > x &&
+	git add x &&
+	! git diff-index --cached --check HEAD
+
+'
+
+test_expect_success 'check with no whitespace errors (diff-tree)' '
+
+	echo "foo();" > x &&
+	git commit -m "new commit" x &&
+	git diff-tree --check HEAD^ HEAD
+
+'
+
+test_expect_success 'check with trailing whitespace (diff-tree)' '
+
+	echo "foo(); " > x &&
+	git commit -m "another commit" x &&
+	! git diff-tree --check HEAD^ HEAD
+
+'
+
+test_expect_success 'check with space before tab in indent (diff-tree)' '
+
+	# indent has space followed by hard tab
+	echo " 	foo();" > x &&
+	git commit -m "yet another" x &&
+	! git diff-tree --check HEAD^ HEAD
+
+'
+
+test_expect_success 'check trailing whitespace (trailing-space: off)' '
+
+	git config core.whitespace "-trailing-space" &&
+	echo "foo ();   " > x &&
+	git diff --check
+
+'
+
+test_expect_success 'check trailing whitespace (trailing-space: on)' '
+
+	git config core.whitespace "trailing-space" &&
+	echo "foo ();   " > x &&
+	! git diff --check
+
+'
+
+test_expect_success 'check space before tab in indent (space-before-tab: off)' '
+
+	# indent contains space followed by HT
+	git config core.whitespace "-space-before-tab" &&
+	echo " 	foo ();" > x &&
+	git diff --check
+
+'
+
+test_expect_success 'check space before tab in indent (space-before-tab: on)' '
+
+	# indent contains space followed by HT
+	git config core.whitespace "space-before-tab" &&
+	echo " 	foo ();   " > x &&
+	! git diff --check
+
+'
+
+test_expect_success 'check spaces as indentation (indent-with-non-tab: off)' '
+
+	git config core.whitespace "-indent-with-non-tab"
+	echo "                foo ();" > x &&
+	git diff --check
+
+'
+
+test_expect_success 'check spaces as indentation (indent-with-non-tab: on)' '
+
+	git config core.whitespace "indent-with-non-tab" &&
+	echo "                foo ();" > x &&
+	! git diff --check
 
 '
 
diff --git a/t/t4017-diff-retval.sh b/t/t4017-diff-retval.sh
index 68731908b..dc0b7126c 100755
--- a/t/t4017-diff-retval.sh
+++ b/t/t4017-diff-retval.sh
@@ -76,4 +76,33 @@ test_expect_success 'git diff-index --cached HEAD' '
 	}
 '
 
+test_expect_success '--check --exit-code returns 0 for no difference' '
+
+	git diff --check --exit-code
+
+'
+
+test_expect_success '--check --exit-code returns 1 for a clean difference' '
+
+	echo "good" > a &&
+	git diff --check --exit-code
+	test $? = 1
+
+'
+
+test_expect_success '--check --exit-code returns 3 for a dirty difference' '
+
+	echo "bad   " >> a &&
+	git diff --check --exit-code
+	test $? = 3
+
+'
+
+test_expect_success '--check with --no-pager returns 2 for dirty difference' '
+
+	git --no-pager diff --check
+	test $? = 2
+
+'
+
 test_done
diff --git a/ws.c b/ws.c
index 52c10caf3..46cbdd637 100644
--- a/ws.c
+++ b/ws.c
@@ -94,3 +94,108 @@ unsigned whitespace_rule(const char *pathname)
 		return whitespace_rule_cfg;
 	}
 }
+
+/* The returned string should be freed by the caller. */
+char *whitespace_error_string(unsigned ws)
+{
+	struct strbuf err;
+	strbuf_init(&err, 0);
+	if (ws & WS_TRAILING_SPACE)
+		strbuf_addstr(&err, "trailing whitespace");
+	if (ws & WS_SPACE_BEFORE_TAB) {
+		if (err.len)
+			strbuf_addstr(&err, ", ");
+		strbuf_addstr(&err, "space before tab in indent");
+	}
+	if (ws & WS_INDENT_WITH_NON_TAB) {
+		if (err.len)
+			strbuf_addstr(&err, ", ");
+		strbuf_addstr(&err, "indent with spaces");
+	}
+	return strbuf_detach(&err, NULL);
+}
+
+/* If stream is non-NULL, emits the line after checking. */
+unsigned check_and_emit_line(const char *line, int len, unsigned ws_rule,
+			     FILE *stream, const char *set,
+			     const char *reset, const char *ws)
+{
+	unsigned result = 0;
+	int leading_space = -1;
+	int trailing_whitespace = -1;
+	int trailing_newline = 0;
+	int i;
+
+	/* Logic is simpler if we temporarily ignore the trailing newline. */
+	if (len > 0 && line[len - 1] == '\n') {
+		trailing_newline = 1;
+		len--;
+	}
+
+	/* Check for trailing whitespace. */
+	if (ws_rule & WS_TRAILING_SPACE) {
+		for (i = len - 1; i >= 0; i--) {
+			if (isspace(line[i])) {
+				trailing_whitespace = i;
+				result |= WS_TRAILING_SPACE;
+			}
+			else
+				break;
+		}
+	}
+
+	/* Check for space before tab in initial indent. */
+	for (i = 0; i < len; i++) {
+		if (line[i] == '\t') {
+			if ((ws_rule & WS_SPACE_BEFORE_TAB) &&
+			    (leading_space != -1))
+				result |= WS_SPACE_BEFORE_TAB;
+			break;
+		}
+		else if (line[i] == ' ')
+			leading_space = i;
+		else
+			break;
+	}
+
+	/* Check for indent using non-tab. */
+	if ((ws_rule & WS_INDENT_WITH_NON_TAB) && leading_space >= 8)
+		result |= WS_INDENT_WITH_NON_TAB;
+
+	if (stream) {
+		/* Highlight errors in leading whitespace. */
+		if ((result & WS_SPACE_BEFORE_TAB) ||
+		    (result & WS_INDENT_WITH_NON_TAB)) {
+			fputs(ws, stream);
+			fwrite(line, leading_space + 1, 1, stream);
+			fputs(reset, stream);
+			leading_space++;
+		}
+		else
+			leading_space = 0;
+
+		/* Now the rest of the line starts at leading_space.
+		 * The non-highlighted part ends at trailing_whitespace. */
+		if (trailing_whitespace == -1)
+			trailing_whitespace = len;
+
+		/* Emit non-highlighted (middle) segment. */
+		if (trailing_whitespace - leading_space > 0) {
+			fputs(set, stream);
+			fwrite(line + leading_space,
+			    trailing_whitespace - leading_space, 1, stream);
+			fputs(reset, stream);
+		}
+
+		/* Highlight errors in trailing whitespace. */
+		if (trailing_whitespace != len) {
+			fputs(ws, stream);
+			fwrite(line + trailing_whitespace,
+			    len - trailing_whitespace, 1, stream);
+			fputs(reset, stream);
+		}
+		if (trailing_newline)
+			fputc('\n', stream);
+	}
+	return result;
+}