[RFC PATCH 3/3] diff: check MIN_BLOCK_LENGTH at start of new block

[Jonathan Tan <jonathantanmy@google.com>]

When noticing that the current line is not the continuation of the
current block, but the start of a new one, mark_color_as_moved() does
not check the length of the current block. Perform that check.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 diff.c                     |  6 +++++-
 t/t4015-diff-whitespace.sh | 45 ++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/diff.c b/diff.c
index 95620b130..04fc0d65d 100644
--- a/diff.c
+++ b/diff.c
@@ -920,7 +920,6 @@ static void mark_color_as_moved(struct diff_options *o,
 		}
 
 		l->flags |= DIFF_SYMBOL_MOVED_LINE;
-		block_length++;
 
 		if (o->color_moved == COLOR_MOVED_PLAIN)
 			continue;
@@ -950,8 +949,13 @@ static void mark_color_as_moved(struct diff_options *o,
 			}
 
 			flipped_block = (flipped_block + 1) % 2;
+
+			adjust_last_block(o, n, block_length);
+			block_length = 0;
 		}
 
+		block_length++;
+
 		if (flipped_block)
 			l->flags |= DIFF_SYMBOL_MOVED_LINE_ALT;
 	}
diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 6f7758e5c..401dc8f08 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -1015,7 +1015,7 @@ test_expect_success 'detect moved code, complete file' '
 	test_cmp expected actual
 '
 
-test_expect_success 'detect malicious moved code, inside file' '
+test_expect_failure 'detect malicious moved code, inside file' '
 	test_config color.diff.oldMoved "normal red" &&
 	test_config color.diff.newMoved "normal green" &&
 	test_config color.diff.oldMovedAlternative "blue" &&
@@ -1417,6 +1417,49 @@ test_expect_success '--color-moved block at end of diff output respects MIN_BLOC
 	test_cmp expected actual
 '
 
+test_expect_success '--color-moved treats adjacent blocks as separate for MIN_BLOCK_LENGTH' '
+	git reset --hard &&
+	cat <<-\EOF >foo &&
+	line1
+	irrelevant_line
+	line2
+	line3
+	EOF
+	>bar &&
+	git add foo bar &&
+	git commit -m x &&
+
+	cat <<-\EOF >foo &&
+	irrelevant_line
+	EOF
+	cat <<-\EOF >bar &&
+	line2
+	line3
+	line1
+	EOF
+
+	git diff HEAD --color-moved=zebra --no-renames | grep -v "index" | test_decode_color >actual &&
+	cat >expected <<-\EOF &&
+	<BOLD>diff --git a/bar b/bar<RESET>
+	<BOLD>--- a/bar<RESET>
+	<BOLD>+++ b/bar<RESET>
+	<CYAN>@@ -0,0 +1,3 @@<RESET>
+	<GREEN>+<RESET><GREEN>line2<RESET>
+	<GREEN>+<RESET><GREEN>line3<RESET>
+	<GREEN>+<RESET><GREEN>line1<RESET>
+	<BOLD>diff --git a/foo b/foo<RESET>
+	<BOLD>--- a/foo<RESET>
+	<BOLD>+++ b/foo<RESET>
+	<CYAN>@@ -1,4 +1 @@<RESET>
+	<RED>-line1<RESET>
+	 irrelevant_line<RESET>
+	<RED>-line2<RESET>
+	<RED>-line3<RESET>
+	EOF
+
+	test_cmp expected actual
+'
+
 test_expect_success 'move detection with submodules' '
 	test_create_repo bananas &&
 	echo ripe >bananas/recipe &&
-- 
2.14.0.434.g98096fd7a8-goog