"diff --check" should affect exit status

"git diff" has a --check option that can be used to check for whitespace
problems but it only reported by printing warnings to the
console.

Now when the --check option is used we give a non-zero exit status,
making "git diff --check" nicer to use in scripts and hooks.

Signed-off-by: Wincent Colaiuta <win@wincent.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

8 files changed, 171 insertions, 18 deletions

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 5d22b7b58c..9ecc1d7bc4 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-diff-files.c b/builtin-diff-files.c
index 046b7e34b5..4afc8724e7 100644
--- a/builtin-diff-files.c
+++ b/builtin-diff-files.c
@@ -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;
 }
diff --git a/builtin-diff-index.c b/builtin-diff-index.c
index 556c506bfa..532b284b10 100644
--- a/builtin-diff-index.c
+++ b/builtin-diff-index.c
@@ -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;
 }
diff --git a/builtin-diff-tree.c b/builtin-diff-tree.c
index 2e13716eec..9ab90cb4c5 100644
--- a/builtin-diff-tree.c
+++ b/builtin-diff-tree.c
@@ -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);
 }
diff --git a/builtin-diff.c b/builtin-diff.c
index 55fb84c730..9d878f6a71 100644
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -247,7 +247,8 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	/* 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))
+	if (!DIFF_OPT_TST(&rev.diffopt, EXIT_WITH_STATUS) &&
+	    (!(rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)))
 		setup_pager();
 
 	/* Do we have --cached and not have a pending object, then
@@ -353,7 +354,8 @@ 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;
diff --git a/diff.c b/diff.c
index 3dd2f35f73..8237075484 100644
--- a/diff.c
+++ b/diff.c
@@ -1031,6 +1031,7 @@ 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)
@@ -1064,6 +1065,7 @@ 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");
@@ -1491,6 +1493,8 @@ 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)
@@ -2121,7 +2125,12 @@ 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)
diff --git a/diff.h b/diff.h
index a52496a108..5d50d93a52 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)
diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 6adf9d11d0..dc538b3e33 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -117,7 +117,6 @@ 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.
@@ -126,4 +125,140 @@ test_expect_success 'check mixed spaces and tabs in indent' '
 
 '
 
+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' '
+
+	# indent has space followed by hard tab
+	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' '
+
+	# 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_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)' '
+
+	# 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_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)' '
+
+	# 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_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)' '
+
+	# indent has space followed by hard tab
+	echo " 	foo();" > x &&
+	git commit -m "yet another" x &&
+	git diff-tree --check HEAD^ HEAD
+
+'
+
 test_done