# [BUG] git diff --(src|dst)-prefix=// causes spurious "(new|deleted) file mode"

2 messages from 2014-05-28 to 2014-05-28. Participants: Noam Postavsky, Junio C Hamano.
Thread: https://gitlist.dev/t/36769

## Noam Postavsky, 2014-05-28 01:55

Subject: [BUG] git diff --(src|dst)-prefix=// causes spurious "(new|deleted) file mode"
Message-ID: <CAM-tV-9vQPPj+TemYnzjRMTjaHqwo3qq=WWJ89VnRMAeYXHZZw@mail.gmail.com>
URL: https://gitlist.dev/e/CAM-tV-9vQPPj%2BTemYnzjRMTjaHqwo3qq%3DWWJ89VnRMAeYXHZZw%40mail.gmail.com

```
% git init
Initialized empty Git repository in /home/npostavs/tmp/scratch/.git/
% echo foo > x
% git add x
% git commit -m x
[master (root-commit) 41be1f2] x
 1 file changed, 1 insertion(+)
 create mode 100644 x
% echo bar > x
% git diff  | head -3
diff --git i/x w/x
index 257cc56..5716ca5 100644
--- i/x
% git diff --dst-prefix=// | head -3
diff --git i/x //x
deleted file mode 100644
index 257cc56..5716ca5 100644
% git diff --src-prefix=// | head -3
diff --git //x w/x
new file mode 100644
index 257cc56..5716ca5 100644
% git diff --src-prefix=// --dst-prefix=// | head -3
diff --git //x //x
new file mode 100644
index 257cc56..5716ca5 100644
% git --version
git version 1.9.2

Background: trying to find a prefix that can't show up in file names
in order to make parsing easier.
https://github.com/magit/magit/pull/1379
https://github.com/magit/magit/pull/1383

```

## Junio C Hamano, 2014-05-28 17:29

Subject: Re: [BUG] git diff --(src|dst)-prefix=// causes spurious "(new|deleted) file mode"
Message-ID: <xmqq38fterrh.fsf@gitster.dls.corp.google.com>
URL: https://gitlist.dev/e/xmqq38fterrh.fsf%40gitster.dls.corp.google.com
In-Reply-To: <CAM-tV-9vQPPj+TemYnzjRMTjaHqwo3qq=WWJ89VnRMAeYXHZZw@mail.gmail.com>

```
Noam Postavsky <npostavs@users.sourceforge.net> writes:

> % git init
> Initialized empty Git repository in /home/npostavs/tmp/scratch/.git/
> % echo foo > x
> % git add x
> % git commit -m x
> [master (root-commit) 41be1f2] x
>  1 file changed, 1 insertion(+)
>  create mode 100644 x
> % echo bar > x
> % git diff  | head -3
> diff --git i/x w/x
> index 257cc56..5716ca5 100644
> --- i/x
> % git diff --dst-prefix=// | head -3
> diff --git i/x //x

The feature these options implement was never designed to accept
anything other than "foo/bar/" (i.e. a relative path-looking thing
that ends with "/" and no funnies such as duplicated slashes, in
order to replace the standard "a/" and "b/").  I think the command
line parsing code of src/dst-prefix trusts the user too much not to
feed nonsense like the above.  They may want to be tightened.

> Background: trying to find a prefix that can't show up in file names
> in order to make parsing easier.
> https://github.com/magit/magit/pull/1379
> https://github.com/magit/magit/pull/1383

It may be worth studying how "git apply" finds what the paths are
and use the same rule for consistency.  IIRC, the rules are roughly:

 - In a renaming/copying patch, you will have "rename/copy from/to"
   header separately.  There is no need to parse the "diff --git"
   line at all;

 - Otherwise, you will have "a/SOMETHING b/SOMETHING" (SOMETHING are
   repeated because there is no rename involved).

```