Re: git merge ignoring whitespace

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Feb 13, 2009, 01:38 UTC
Message-ID: <alpine.DEB.1.00.0902130231300.26370@racer>
In-Reply-To: <2754.1233876289@relay.known.net>

Hi,

On Thu, 5 Feb 2009, layer wrote:

Show 15 quoted lines

> Junio, on 3/25/07 you said:
> 
>   I know Linus does not like applying patches with whitespace
>   fuzziness, but I personally think a merge that ignores
>   whitespace changes would be a useful thing to have, without
>   having to call an external specialized merge backend. In other
>   words, I do not think it is so special a thing to want to, but
>   it is rather an unfortunate norm.  I am not opposed to give
>   git-merge-recursive a command line option to tell it to merge
>   ignoring the whitespace-only changes, when it does the 3-way
>   file-level merge internally.
> 
> Whatever came of this?  I tried giving git merge a --ignore-whitespace
> argument and the error message that followed show no equivalent
> argument.

I can think of two issues:

- there was this -X patch by Junio, but I think it is a bad interface to 
  pass merge backend options, as it is not closely coupled with the 
  backend.  Just imagine this:

	git merge -X ignore-whitespace -s resolve,recursive

  Does the "-X ignore-whitespace" impact resolve, recursive, or both?  And 
  we'd need some way to specify the option to the backend.  I thought that

	git merge -s resolve,recursive/ignore-whitespace

  would be a sane syntax, but at least _I_ did not have a need to pass 
  backend options yet.

- more fundamental, how should the merge ignoring whitespace work?  Which 
  version would it take if the lines agree _except_ for whitespace 
  changes?  This needs to be well designed, as we have not only merges 
  (where we have "ours" and "theirs"), but also rebases (where we have 
  "theirs" and _then_ "ours"), and of course recursive merges when there 
  is more than a single merge base (and there, it gets really nasty, so 
  you better have the semantics of the whitespace-ignoring merge put down 
  quite clearly).

> It would sure come in handy right now.  Is there some other way to do
> it that I didn't find searching the mailing list?

Of course, you could try to "normalize" the whitespace, and perform the merge after that.

Ciao, Dscho