From: Jeff King <peff@peff.net>
Date: Sat, 04 Oct 2008 04:17:14 GMT
Subject: Re: git apply: git diff header lacks filename information for git diff --no-index patch
Message-ID: <20081004041714.GA12413@coredump.intra.peff.net>
In-Reply-To: <500f3d130810021127j570bb540p901f6a73f58a6cb1@mail.gmail.com>

On Thu, Oct 02, 2008 at 09:27:36PM +0300, Imre Deak wrote:

> $ git apply patch
> fatal: git diff header lacks filename information (line 4)
> $ cat patch
> diff --git a/dev/null b/a
> new file mode 100644
> index 0000000000000000000000000000000000000000..1f2a4f5ef3df7f7456d91c961da36fc58904f2f1
> GIT binary patch

Hmm. The problem is that "git apply" doesn't accept that "a/dev/null"
and "b/a" are the same, so it rejects them as a name. I guess on a text
patch, we would just pull that information from the "---" and "+++"
lines, so we don't care that it's not on the diff commandline.

However, a _non_ --no-index patch doesn't produce the same output. It
will actually produce the line:

  diff --git a/a b/a

even if it is a creation patch. So I'm not sure which piece of code is
at fault. Either:

  1. git apply is right to reject, and "git diff --no-index" should be
     putting the actual filename on the commandline of a binary patch
     instead of /dev/null, even if it is a creation patch.

     or

  2. git apply should accept this construct. Perhaps we should relax the
     "both names must be the same" rule if one of the names is /dev/null
     (and we would take the other)?

Linus, the "both names must be the same" code in git_header_name blames
to you (5041aa70). Thoughts on number 2?

-Peff