[PATCH] diffcore: fix iteration order of identical files during rename detection
- From
SZEDER Gábor <szeder@ira.uka.de>
- Date
- Mar 30, 2016, 08:35 UTC
- Message-ID
- <1459326907-16179-1-git-send-email-szeder@ira.uka.de>
If the two paths 'dir/A/file' and 'dir/B/file' have identical content and the parent directory is renamed, e.g. 'git mv dir other-dir', then diffcore reports the following exact renames:
renamed: dir/B/file -> other-dir/A/file
renamed: dir/A/file -> other-dir/B/fileWhile technically not wrong, this is confusing not only for the user, but also for git commands that make decisions based on rename information, e.g. 'git log --follow other-dir/A/file' follows 'dir/B/file' past the rename.
This behavior is a side effect of commit v2.0.0-rc4~8^2~14 (diffcore-rename.c: simplify finding exact renames, 2013-11-14): the hashmap storing sources returns entries from the same bucket, i.e. sources matching the current destination, in LIFO order. Thus the iteration first examines 'other-dir/A/file' and 'dir/B/file' and, upon finding identical content and basename, reports an exact rename.
Other hashmap users are apparently happy with the current iteration order over the entries of a bucket. Changing the iteration order would risk upsetting other hashmap users and would increase the memory footprint of each bucket by a pointer to the tail element.
Fill the hashmap with source entries in reverse order to restore the original exact rename detection behavior.
Reported-by: Bill Okara <billokara@gmail.com> Signed-off-by: SZEDER Gábor <szeder@ira.uka.de> ---
Resend of the patch, with a slightly updated commit message, included in
http://thread.gmane.org/gmane.comp.version-control.git/287281/focus=287570
Being embedded with scissors in an email without Junio among the recipients on the day the first -rc was tagged... no wonder it flew below the radar.
diffcore-rename.c | 6 ++++-- t/t4001-diff-rename.sh | 11 +++++++++++ 2 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/diffcore-rename.c b/diffcore-rename.c index 3b3c1ed535e7..7f03eb5a0404 100644 --- a/diffcore-rename.c +++ b/diffcore-rename.c @@ -340,9 +340,11 @@ static int find_exact_renames(struct diff_options *options) int i, renames = 0; struct hashmap file_table; - /* Add all sources to the hash table */ + /* Add all sources to the hash table in reverse order, because + * later on they will be retrieved in LIFO order. + */ hashmap_init(&file_table, NULL, rename_src_nr); - for (i = 0; i < rename_src_nr; i++) + for (i = rename_src_nr-1; i >= 0; i--) insert_file_table(&file_table, i, rename_src[i].p->one); /* Walk the destinations and find best source match */ diff --git a/t/t4001-diff-rename.sh b/t/t4001-diff-rename.sh index 2f327b749588..ed90c6c6f984 100755 --- a/t/t4001-diff-rename.sh +++ b/t/t4001-diff-rename.sh @@ -77,6 +77,17 @@ test_expect_success 'favour same basenames even with minor differences' ' git show HEAD:path1 | sed "s/15/16/" > subdir/path1 && git status | test_i18ngrep "renamed: .*path1 -> subdir/path1"' +test_expect_success 'two files with same basename and same content' ' + git reset --hard && + mkdir -p dir/A dir/B && + cp path1 dir/A/file && + cp path1 dir/B/file && + git add dir && + git commit -m 2 && + git mv dir other-dir && + git status | test_i18ngrep "renamed: .*dir/A/file -> other-dir/A/file" +' + test_expect_success 'setup for many rename source candidates' ' git reset --hard && for i in 0 1 2 3 4 5 6 7 8 9;
-- 2.8.0.46.gb821760