Re: git mv messed up file mapping if folders contain identical files

[Bill Okara <billokara@gmail.com>]

Hi,

On Fri, Feb 26, 2016 at 4:50 AM, SZEDER Gábor <szeder@ira.uka.de> wrote:
>
> Please don't top-post on this list.
>
Sorry about that. Just learned what that means and why it is bad...

> Subject: [PATCH] diffcore: fix iteration order of identical files during rename detection
>
> 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/file
>
> While 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'.
>
> 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.
>
> Restore the original behavior by reversing the order of filling the
> hashmap with source entries.
>
> Reported-by: Bill Okara <billokara@gmail.com>
> Signed-off-by: SZEDER Gábor <szeder@ira.uka.de>
> ---
>  diffcore-rename.c      |  6 ++++--
>  t/t4001-diff-rename.sh | 11 +++++++++++
>  2 files changed, 15 insertions(+), 2 deletions(-)

> 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;
> --
> 2.7.2.410.g92cb358
>

Thank you very much for the fix and the detailed explanation!

-Bill