Re: detecting rename->commit->modify->commit

From: Jeff King <peff@peff.net>
Date: May 1, 2008, 14:45 UTC
Message-ID: <20080501144524.GA10876@sigill.intra.peff.net>
In-Reply-To: <4819CF50.2020509@tikalk.com>

On Thu, May 01, 2008 at 05:10:24PM +0300, Ittay Dror wrote:

> Say I have a file A, I rename to 'B', commit, then change file B and  
> commit. Does 'git diff -M HEAD^^..' detect that? From what I see now, it  
> will show 'B' as new (all of it with '+' prefix in the output). Am I 
> right?

Yes, it should find it, assuming the changes to B leave it recognizable. Try:

  mkdir repo && cd repo && git init
  cp /usr/share/dict/words A
  git add . && git commit -m added
  mv A B && git add B && git commit -a -m rename
  echo change >>B && git commit -a -m change
  git diff -M HEAD^^.. | head -n 7

You should see something like:

  diff --git a/A b/B
  similarity index 99%
  rename from A
  rename to B
  index 8e50f11..6525618 100644
  --- a/A
  +++ b/B

However, note the similarity index. If you change B so much that it doesn't look close to the original A, then the rename is not detected (and intentionally so -- the argument is that it is no longer a rename in that context, but a rewritten file).

-Peff