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--dirstat-by-file: Make it faster and more correct

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 object for a file has changed. We therefore only need to compare the object names of each file pair in the diff queue and we can skip the entire --dirstat analysis and simply set 'damage' to 1 for each entry where the object name 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@herland.net> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Johan Herland committed Apr 11, 2011 at 00:48 UTC 0133dab75d8b15c559aa9df66134d72dce0e0476

3 files changed +25 -5

diff.c

+20 -5

@@ -1539,9 +1539,27 @@ static void show_dirstat(struct diff_options *options)

1539 struct diff_filepair *p = q->queue[i];

1540 const char *name;

1541 unsigned long copied, added, damage;

1542 + int content_changed;

1543

1544 name = p->one->path ? p->one->path : p->two->path;

1545

1546 + if (p->one->sha1_valid && p->two->sha1_valid)

1547 + content_changed = hashcmp(p->one->sha1, p->two->sha1);

1548 + else

1549 + content_changed = 1;

1550 +

1551 + if (DIFF_OPT_TST(options, DIRSTAT_BY_FILE)) {

1552 + /*

1553 + * In --dirstat-by-file mode, we don't really need to

1554 + * look at the actual file contents at all.

1555 + * The fact that the SHA1 changed is enough for us to

1556 + * add this file to the list of results

1557 + * (with each file contributing equal damage).

1558 + */

1559 + damage = content_changed ? 1 : 0;

1560 + goto found_damage;

1561 + }

1562 +

1563 if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {

1564 diff_populate_filespec(p->one, 0);

1565 diff_populate_filespec(p->two, 0);

@@ -1564,14 +1582,11 @@ static void show_dirstat(struct diff_options *options)

1582 /*

1583 * Original minus copied is the removed material,

1584 * added is the new material. They are both damages

1567 - * made to the preimage. In --dirstat-by-file mode, count

1568 - * damaged files, not damaged lines. This is done by

1569 - * counting only a single damaged line per file.

1585 + * made to the preimage.

1586 */

1587 damage = (p->one->size - copied) + added;

1572 - if (DIFF_OPT_TST(options, DIRSTAT_BY_FILE) && damage > 0)

1573 - damage = 1;

1588

1589 +found_damage:

1590 ALLOC_GROW(dir.files, dir.nr + 1, dir.alloc);

1591 dir.files[dir.nr].name = name;

1592 dir.files[dir.nr].changed = damage;

t/t4013-diff-various.sh

@@ -302,6 +302,8 @@ diff master master^ side

302 diff --dirstat master~1 master~2

303 # --dirstat doesn't notice changes that simply rearrange existing lines

304 diff --dirstat initial rearrange

305 +# ...but --dirstat-by-file does notice changes that only rearrange lines

306 +diff --dirstat-by-file initial rearrange

307 EOF

308

309 test_expect_success 'log -S requires an argument' '

t/t4013/diff.diff_--dirstat-by-file_initial_rearrange new

@@ -0,0 +1,3 @@

1 +$ git diff --dirstat-by-file initial rearrange

2 + 100.0% dir/

3 +$