Currently, when using --dirstat-by-file, it first does the full --dirstat
analysis (using diffcore_count_changes()), and then resets 'damage' to 1,
if any damage was found by diffcore_count_changes().
But --dirstat-by-file is not interested in the file damage per se. It only
cares if the file changed at all. In that sense it only cares if the blob
SHA1 for a file has changed. We therefore only need to compare the SHA1s
of each file pair in the diff queue. As a result, we can skip the entire
--dirstat analysis and simply set 'damage' to 1 for each entry where the
SHA1 has changed.
This makes --dirstat-by-file faster, and also bypasses --dirstat's practice
of ignoring rearranged lines within a file.
The patch also contains an added testcase verifying that --dirstat-by-file
now detects changes that only rearrange lines within a file.
Signed-off-by: Johan Herland <johan@xxxxxxxxxxx>
---
diff.c | 25 ++++++++++++++++----
t/t4013-diff-various.sh | 2 +
.../diff.diff_--dirstat-by-file_initial_rearrange | 3 ++
3 files changed, 25 insertions(+), 5 deletions(-)
create mode 100644 t/t4013/diff.diff_--dirstat-by-file_initial_rearrange
diff --git a/diff.c b/diff.c
index 9fa8410..a224048 100644
--- a/diff.c
+++ b/diff.c
@@ -1538,9 +1538,27 @@ static void show_dirstat(struct diff_options *options)
struct diff_filepair *p = q->queue[i];
const char *name;
unsigned long copied, added, damage;
+ int content_changed;
name = p->one->path ? p->one->path : p->two->path;
+ if (p->one->sha1_valid && p->two->sha1_valid)
+ content_changed = hashcmp(p->one->sha1, p->two->sha1);
+ else
+ content_changed = 1;
+
+ if (DIFF_OPT_TST(options, DIRSTAT_BY_FILE)) {
+ /*
+ * In --dirstat-by-file mode, we don't really need to
+ * look at the actual file contents at all.
+ * The fact that the SHA1 changed is enough for us to
+ * add this file to the list of results
+ * (with each file contributing equal damage).
+ */
+ damage = content_changed ? 1 : 0;
+ goto found_damage;
+ }
+
if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
diff_populate_filespec(p->one, 0);
diff_populate_filespec(p->two, 0);
@@ -1563,14 +1581,11 @@ static void show_dirstat(struct diff_options *options)
/*
* Original minus copied is the removed material,
* added is the new material. They are both damages
- * made to the preimage. In --dirstat-by-file mode, count
- * damaged files, not damaged lines. This is done by
- * counting only a single damaged line per file.
+ * made to the preimage.
*/
damage = (p->one->size - copied) + added;
- if (DIFF_OPT_TST(options, DIRSTAT_BY_FILE) && damage > 0)
- damage = 1;
+found_damage:
ALLOC_GROW(dir.files, dir.nr + 1, dir.alloc);
dir.files[dir.nr].name = name;
dir.files[dir.nr].changed = damage;
diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 3b1b392..6428a90 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -302,6 +302,8 @@ diff master master^ side
diff --dirstat master~1 master~2
# --dirstat doesn't notice changes that simply rearrange existing lines
diff --dirstat initial rearrange
+# ...but --dirstat-by-file does notice changes that only rearrange lines
+diff --dirstat-by-file initial rearrange
EOF
test_expect_success 'log -S requires an argument' '
diff --git a/t/t4013/diff.diff_--dirstat-by-file_initial_rearrange b/t/t4013/diff.diff_--dirstat-by-file_initial_rearrange
new file mode 100644
index 0000000..e48e33f
--- /dev/null
+++ b/t/t4013/diff.diff_--dirstat-by-file_initial_rearrange
@@ -0,0 +1,3 @@
+$ git diff --dirstat-by-file initial rearrange
+ 100.0% dir/
+$
--
1.7.5.rc1.3.g4d7b
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