The existing behavior of diff --color-moved=zebra does not define the
minimum size of a block at all, instead relying on a heuristic applied
later to filter out sets of adjacent moved lines that are shorter than 3
lines long. This can be confusing, because a block could thus be colored
as moved at the source but not at the destination (or vice versa),
depending on its neighbors.
Instead, teach diff that the minimum size of a block is 10
non-whitespace characters. This allows diff to still exclude
uninteresting lines appearing on their own (such as those solely
consisting of one or a few closing braces), as was the intention of the
adjacent-moved-line heuristic.
This requires a change in the test "detect malicious moved code, inside
file" in that some of its lines are no longer considered to be part of a
block, because they are too short. The malicious move can still be
observed, however.
Signed-off-by: Jonathan Tan <jonathantanmy@xxxxxxxxxx>
---
Documentation/diff-options.txt | 8 ++--
diff.c | 27 +++++++++---
diff.h | 2 +-
t/t4015-diff-whitespace.sh | 96 +++++++++++++++++++++++++++++++++++++++---
4 files changed, 113 insertions(+), 20 deletions(-)
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index bc52bd0b9..d0bdc849f 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -254,13 +254,11 @@ plain::
moved line, but it is not very useful in a review to determine
if a block of code was moved without permutation.
zebra::
- Blocks of moved code are detected greedily. The detected blocks are
+ Blocks of moved text of at least 10 non-whitespace characters
+ are detected greedily. The detected blocks are
painted using either the 'color.diff.{old,new}Moved' color or
'color.diff.{old,new}MovedAlternative'. The change between
- the two colors indicates that a new block was detected. If there
- are fewer than 3 adjacent moved lines, they are not marked up
- as moved, but the regular colors 'color.diff.{old,new}' will be
- used.
+ the two colors indicates that a new block was detected.
dimmed_zebra::
Similar to 'zebra', but additional dimming of uninteresting parts
of moved code is performed. The bordering lines of two adjacent
diff --git a/diff.c b/diff.c
index f598d8a3a..305ce4126 100644
--- a/diff.c
+++ b/diff.c
@@ -864,19 +864,28 @@ static int shrink_potential_moved_blocks(struct moved_entry **pmb,
/*
* If o->color_moved is COLOR_MOVED_PLAIN, this function does nothing.
*
- * Otherwise, if the last block has fewer lines than
- * COLOR_MOVED_MIN_BLOCK_LENGTH, unset DIFF_SYMBOL_MOVED_LINE on all lines in
- * that block.
+ * Otherwise, if the last block has fewer non-space characters than
+ * COLOR_MOVED_MIN_NON_SPACE_COUNT, unset DIFF_SYMBOL_MOVED_LINE on all lines
+ * in that block.
*
* The last block consists of the (n - block_length)'th line up to but not
* including the nth line.
*/
static void adjust_last_block(struct diff_options *o, int n, int block_length)
{
- int i;
- if (block_length >= COLOR_MOVED_MIN_BLOCK_LENGTH ||
- o->color_moved == COLOR_MOVED_PLAIN)
+ int i, non_space_count = 0;
+ if (o->color_moved == COLOR_MOVED_PLAIN)
return;
+ for (i = 1; i < block_length + 1; i++) {
+ const char *c = o->emitted_symbols->buf[n - i].line;
+ for (; *c; c++) {
+ if (isspace(*c))
+ continue;
+ non_space_count++;
+ if (non_space_count >= COLOR_MOVED_MIN_NON_SPACE_COUNT)
+ return;
+ }
+ }
for (i = 1; i < block_length + 1; i++)
o->emitted_symbols->buf[n - i].flags &= ~DIFF_SYMBOL_MOVED_LINE;
}
@@ -923,7 +932,6 @@ 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;
@@ -953,8 +961,13 @@ 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/diff.h b/diff.h
index 5755f465d..9e2fece5b 100644
--- a/diff.h
+++ b/diff.h
@@ -195,7 +195,7 @@ struct diff_options {
COLOR_MOVED_ZEBRA_DIM = 3,
} color_moved;
#define COLOR_MOVED_DEFAULT COLOR_MOVED_ZEBRA
- #define COLOR_MOVED_MIN_BLOCK_LENGTH 3
+ #define COLOR_MOVED_MIN_NON_SPACE_COUNT 10
};
void diff_emit_submodule_del(struct diff_options *o, const char *line);
diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index 6f7758e5c..d8e7b77b9 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -1101,9 +1101,9 @@ test_expect_success 'detect malicious moved code, inside file' '
<BRED>-{<RESET>
<BLUE>-if (!u->is_allowed_foo)<RESET>
<BLUE>-return;<RESET>
- <BRED>-foo(u);<RESET>
- <BLUE>-}<RESET>
- <BLUE>-<RESET>
+ <RED>-foo(u);<RESET>
+ <RED>-}<RESET>
+ <RED>-<RESET>
int main()<RESET>
{<RESET>
foo();<RESET>
@@ -1117,11 +1117,11 @@ test_expect_success 'detect malicious moved code, inside file' '
<RESET>
<BGREEN>+<RESET><BGREEN>int secure_foo(struct user *u)<RESET>
<BGREEN>+<RESET><BGREEN>{<RESET>
- <YELLOW>+<RESET><YELLOW>foo(u);<RESET>
+ <GREEN>+<RESET><GREEN>foo(u);<RESET>
<BGREEN>+<RESET><BGREEN>if (!u->is_allowed_foo)<RESET>
<BGREEN>+<RESET><BGREEN>return;<RESET>
- <YELLOW>+<RESET><YELLOW>}<RESET>
- <YELLOW>+<RESET>
+ <GREEN>+<RESET><GREEN>}<RESET>
+ <GREEN>+<RESET>
int another_function()<RESET>
{<RESET>
bar();<RESET>
@@ -1382,7 +1382,7 @@ EOF
test_cmp expected actual
'
-test_expect_success '--color-moved block at end of diff output respects MIN_BLOCK_LENGTH' '
+test_expect_success '--color-moved block at end of diff output respects MIN_NON_SPACE_COUNT' '
git reset --hard &&
>bar &&
cat <<-\EOF >foo &&
@@ -1417,6 +1417,88 @@ test_expect_success '--color-moved block at end of diff output respects MIN_BLOC
test_cmp expected actual
'
+test_expect_success '--color-moved respects MIN_NON_SPACE_COUNT' '
+ git reset --hard &&
+ cat <<-\EOF >foo &&
+ nine chars
+ irrelevant_line
+ ten chars__
+ EOF
+ >bar &&
+ git add foo bar &&
+ git commit -m x &&
+
+ cat <<-\EOF >foo &&
+ irrelevant_line
+ EOF
+ cat <<-\EOF >bar &&
+ ten chars__
+ nine chars
+ 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 +1,2 @@<RESET>
+ <BOLD;CYAN>+<RESET><BOLD;CYAN>ten chars__<RESET>
+ <GREEN>+<RESET><GREEN>nine chars<RESET>
+ <BOLD>diff --git a/foo b/foo<RESET>
+ <BOLD>--- a/foo<RESET>
+ <BOLD>+++ b/foo<RESET>
+ <CYAN>@@ -1,3 +1 @@<RESET>
+ <RED>-nine chars<RESET>
+ irrelevant_line<RESET>
+ <BOLD;MAGENTA>-ten chars__<RESET>
+ EOF
+
+ test_cmp expected actual
+'
+
+test_expect_success '--color-moved treats adjacent blocks as separate for MIN_NON_SPACE_COUNT' '
+ git reset --hard &&
+ cat <<-\EOF >foo &&
+ lin1
+ irrelevant_line
+ lin2
+ lin3
+ EOF
+ >bar &&
+ git add foo bar &&
+ git commit -m x &&
+
+ cat <<-\EOF >foo &&
+ irrelevant_line
+ EOF
+ cat <<-\EOF >bar &&
+ lin2
+ lin3
+ lin1
+ 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>lin2<RESET>
+ <GREEN>+<RESET><GREEN>lin3<RESET>
+ <GREEN>+<RESET><GREEN>lin1<RESET>
+ <BOLD>diff --git a/foo b/foo<RESET>
+ <BOLD>--- a/foo<RESET>
+ <BOLD>+++ b/foo<RESET>
+ <CYAN>@@ -1,4 +1 @@<RESET>
+ <RED>-lin1<RESET>
+ irrelevant_line<RESET>
+ <RED>-lin2<RESET>
+ <RED>-lin3<RESET>
+ EOF
+
+ test_cmp expected actual
+'
+
test_expect_success 'move detection with submodules' '
test_create_repo bananas &&
echo ripe >bananas/recipe &&
--
2.14.1.480.gb18f417b89-goog
