[RFC PATCH 0/3 UPDATED] diff --check enhancements

@@ -175,19 +175,19 @@ endif::git-format-patch[]
 	Shorthand for "--text".
 
 --ignore-space-at-eol::
-	Ignore changes in white spaces at EOL.
+	Ignore changes in whitespace at EOL.
 
 --ignore-space-change::
-	Ignore changes in amount of white space.  This ignores white
-	space at line end, and consider all other sequences of one or
-	more white space characters to be equivalent.
+	Ignore changes in amount of whitespace.  This ignores whitespace
+	at line end, and considers all other sequences of one or
+	more whitespace characters to be equivalent.
 
 -b::
 	Shorthand for "--ignore-space-change".
 
 --ignore-all-space::
-	Ignore white space when comparing lines.  This ignores
-	difference even if one line has white space where the other
+	Ignore whitespace when comparing lines.  This ignores
+	differences even if one line has whitespace where the other
 	line has none.
 
 -w::

@@ -245,7 +245,7 @@ This commit is referred to as a "merge commit", or sometimes just a
 	of the object's contents using the Secure Hash Algorithm
 	1 and usually represented by the 40 character hexadecimal encoding of
 	the <<def_hash,hash>> of the object (possibly followed by
-	a white space).
+	whitespace).
 
 [[def_object_type]]object type::
 	One of the identifiers

@@ -1015,7 +1015,7 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
 		if (line[i - 1] == '\t' && spaces)
 			space_before_tab = 1;
 
-		/* check white space at line end */
+		/* check whitespace at line end */
 		if (line[len - 1] == '\n')
 			len--;
 		if (isspace(line[len - 1]))

@@ -1029,7 +1029,7 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
 					putchar(',');
 			}
 			if (white_space_at_end)
-				printf("white space at end");
+				printf("whitespace at end");
 			printf(":%s ", reset);
 			emit_line_with_ws(1, set, reset, ws, line, len,
 					  data->ws_rule);

@@ -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

@@ -33,5 +33,7 @@ int cmd_diff_files(int argc, const char **argv, const char *prefix)
 	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;
+	if (rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
+		return DIFF_OPT_TST(&rev.diffopt, CHECK_FAILED) != 0;
 	return result;
 }

@@ -46,5 +46,7 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	result = run_diff_index(&rev, cached);
 	if (DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
 		return DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0;
+	if (rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
+		return DIFF_OPT_TST(&rev.diffopt, CHECK_FAILED) != 0;
 	return result;
 }

@@ -117,23 +117,23 @@ 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);
 	}
+	if (opt->diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
+		return DIFF_OPT_TST(&opt->diffopt, CHECK_FAILED) != 0;
 	return DIFF_OPT_TST(&opt->diffopt, EXIT_WITH_STATUS)
 		&& DIFF_OPT_TST(&opt->diffopt, HAS_CHANGES);
 }

@@ -365,7 +365,8 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 					     ent, ents);
 	if (DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS))
 		result = DIFF_OPT_TST(&rev.diffopt, HAS_CHANGES) != 0;
-
+	if (rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
+		return DIFF_OPT_TST(&rev.diffopt, CHECK_FAILED) != 0;
 	if (1 < rev.diffopt.skip_stat_unmatch)
 		refresh_index_quietly();
 	return result;

@@ -996,6 +996,7 @@ struct checkdiff_t {
 	const char *filename;
 	int lineno, color_diff;
 	unsigned ws_rule;
+	int status;
 };
 
 static void checkdiff_consume(void *priv, char *line, unsigned long len)

@@ -1022,6 +1023,7 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
 			white_space_at_end = 1;
 
 		if (space_before_tab || white_space_at_end) {
+			data->status = 1;
 			printf("%s:%d: %s", data->filename, data->lineno, ws);
 			if (space_before_tab) {
 				printf("space before tab");

@@ -1412,7 +1414,7 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 	diff_free_filespec_data(two);
 }
 
-static void builtin_checkdiff(const char *name_a, const char *name_b,
+static int builtin_checkdiff(const char *name_a, const char *name_b,
 			     struct diff_filespec *one,
 			     struct diff_filespec *two, struct diff_options *o)
 {

@@ -1420,7 +1422,7 @@ static void builtin_checkdiff(const char *name_a, const char *name_b,
 	struct checkdiff_t data;
 
 	if (!two)
-		return;
+		return 0;
 
 	memset(&data, 0, sizeof(data));
 	data.xm.consume = checkdiff_consume;

@@ -1449,6 +1451,7 @@ 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);
+	return data.status;
 }
 
 struct diff_filespec *alloc_filespec(const char *path)

@@ -2033,14 +2036,14 @@ static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
 	builtin_diffstat(name, other, p->one, p->two, diffstat, o, complete_rewrite);
 }
 
-static void run_checkdiff(struct diff_filepair *p, struct diff_options *o)
+static int run_checkdiff(struct diff_filepair *p, struct diff_options *o)
 {
 	const char *name;
 	const char *other;
 
 	if (DIFF_PAIR_UNMERGED(p)) {
 		/* unmerged */
-		return;
+		return 0;
 	}
 
 	name = p->one->path;

@@ -2049,7 +2052,7 @@ static void run_checkdiff(struct diff_filepair *p, struct diff_options *o)
 	diff_fill_sha1_info(p->one);
 	diff_fill_sha1_info(p->two);
 
-	builtin_checkdiff(name, other, p->one, p->two, o);
+	return builtin_checkdiff(name, other, p->one, p->two, o);
 }
 
 void diff_setup(struct diff_options *options)

@@ -2079,7 +2082,12 @@ int diff_setup_done(struct diff_options *options)
 	if (options->output_format & DIFF_FORMAT_NAME_STATUS)
 		count++;
 	if (options->output_format & DIFF_FORMAT_CHECKDIFF)
+	{
 		count++;
+		if (DIFF_OPT_TST(options, QUIET) ||
+		    DIFF_OPT_TST(options, EXIT_WITH_STATUS))
+			die("--check may not be used with --quiet or --exit-code");
+	}
 	if (options->output_format & DIFF_FORMAT_NO_OUTPUT)
 		count++;
 	if (count > 1)

@@ -2546,17 +2554,17 @@ static void diff_flush_stat(struct diff_filepair *p, struct diff_options *o,
 	run_diffstat(p, o, diffstat);
 }
 
-static void diff_flush_checkdiff(struct diff_filepair *p,
+static int diff_flush_checkdiff(struct diff_filepair *p,
 		struct diff_options *o)
 {
 	if (diff_unmodified_pair(p))
-		return;
+		return 0;
 
 	if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
 	    (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
-		return; /* no tree diffs in patch format */
+		return 0; /* no tree diffs in patch format */
 
-	run_checkdiff(p, o);
+	return run_checkdiff(p, o);
 }
 
 int diff_queue_is_empty(void)

@@ -2675,16 +2683,19 @@ static int check_pair_status(struct diff_filepair *p)
 	}
 }
 
-static void flush_one_pair(struct diff_filepair *p, struct diff_options *opt)
+static int flush_one_pair(struct diff_filepair *p, struct diff_options *opt)
 {
 	int fmt = opt->output_format;
 
 	if (fmt & DIFF_FORMAT_CHECKDIFF)
-		diff_flush_checkdiff(p, opt);
+		return diff_flush_checkdiff(p, opt);
 	else if (fmt & (DIFF_FORMAT_RAW | DIFF_FORMAT_NAME_STATUS))
 		diff_flush_raw(p, opt);
 	else if (fmt & DIFF_FORMAT_NAME)
 		write_name_quoted(p->two->path, stdout, opt->line_termination);
+
+	/* return value only matters with DIFF_FORMAT_CHECKDIFF */
+	return 0;
 }
 
 static void show_file_mode_name(const char *newdelete, struct diff_filespec *fs)

@@ -2923,8 +2934,8 @@ void diff_flush(struct diff_options *options)
 			     DIFF_FORMAT_CHECKDIFF)) {
 		for (i = 0; i < q->nr; i++) {
 			struct diff_filepair *p = q->queue[i];
-			if (check_pair_status(p))
-				flush_one_pair(p, options);
+			if (check_pair_status(p) && flush_one_pair(p, options))
+				DIFF_OPT_SET(options, CHECK_FAILED);
 		}
 		separator++;
 	}

@@ -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)

@@ -117,4 +117,135 @@ EOF
 git diff -b > out
 test_expect_success 'another test, with -b' 'git diff expect out'
 
+test_expect_success 'check with no whitespace errors' '
+
+	git commit -m "snapshot" &&
+	echo "foo();" > x &&
+	git diff --check
+
+'
+
+test_expect_failure 'check with trailing whitespace' '
+
+	echo "foo(); " > x &&
+	git diff --check
+
+'
+
+test_expect_failure 'check with space before tab in indent' '
+
+	echo " 	foo();" > x &&
+	git diff --check
+
+'
+
+test_expect_failure '--check and --exit-code are exclusive' '
+
+	git checkout x &&
+	git diff --check --exit-code
+
+'
+
+test_expect_failure '--check and --quiet are 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_failure 'check staged with trailing whitespace' '
+
+	echo "foo(); " > x &&
+	git add x &&
+	git diff --cached --check
+
+'
+
+test_expect_failure 'check staged with space before tab in indent' '
+
+	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_failure 'check with trailing whitespace (diff-index)' '
+
+	echo "foo(); " > x &&
+	git add x &&
+	git diff-index --check HEAD
+
+'
+
+test_expect_failure 'check with space before tab in indent (diff-index)' '
+
+	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_failure 'check staged with trailing whitespace (diff-index)' '
+
+	echo "foo(); " > x &&
+	git add x &&
+	git diff-index --cached --check HEAD
+
+'
+
+test_expect_failure 'check staged with space before tab in indent (diff-index)' '
+
+	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_failure 'check with trailing whitespace (diff-tree)' '
+
+	echo "foo(); " > x &&
+	git commit -m "another commit" x &&
+	git diff-tree --check HEAD^ HEAD
+
+'
+
+test_expect_failure 'check with space before tab in indent (diff-tree)' '
+
+	echo " 	foo();" > x &&
+	git commit -m "yet another" x &&
+	git diff-tree --check HEAD^ HEAD
+
+'
+
 test_done

@@ -7,64 +7,11 @@
 #
 # To enable this hook, make this file executable.
 
-# This is slightly modified from Andrew Morton's Perfect Patch.
-# Lines you introduce should not have trailing whitespace.
-# Also check for an indentation that has SP before a TAB.
+git-diff-index -M --cached --check HEAD -- && exit 0
 
-if git-rev-parse --verify HEAD 2>/dev/null
-then
-	git-diff-index -p -M --cached HEAD --
-else
-	# NEEDSWORK: we should produce a diff with an empty tree here
-	# if we want to do the same verification for the initial import.
-	:
-fi |
-perl -e '
-    my $found_bad = 0;
-    my $filename;
-    my $reported_filename = "";
-    my $lineno;
-    sub bad_line {
-	my ($why, $line) = @_;
-	if (!$found_bad) {
-	    print STDERR "*\n";
-	    print STDERR "* You have some suspicious patch lines:\n";
-	    print STDERR "*\n";
-	    $found_bad = 1;
-	}
-	if ($reported_filename ne $filename) {
-	    print STDERR "* In $filename\n";
-	    $reported_filename = $filename;
-	}
-	print STDERR "* $why (line $lineno)\n";
-	print STDERR "$filename:$lineno:$line\n";
-    }
-    while (<>) {
-	if (m|^diff --git a/(.*) b/\1$|) {
-	    $filename = $1;
-	    next;
-	}
-	if (/^@@ -\S+ \+(\d+)/) {
-	    $lineno = $1 - 1;
-	    next;
-	}
-	if (/^ /) {
-	    $lineno++;
-	    next;
-	}
-	if (s/^\+//) {
-	    $lineno++;
-	    chomp;
-	    if (/\s$/) {
-		bad_line("trailing whitespace", $_);
-	    }
-	    if (/^\s* \t/) {
-		bad_line("indent SP followed by a TAB", $_);
-	    }
-	    if (/^(?:[<>=]){7}/) {
-		bad_line("unresolved merge conflict", $_);
-	    }
-	}
-    }
-    exit($found_bad);
-'
+cat >&2 <<EOF
+fatal: commit aborted due to whitespace problems
+specify --no-verify to bypass these checks and commit anyway
+EOF
+
+exit 1