git merge ignoring whitespace

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.

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?

Thanks.

Kevin

layer <layer@known.net> writes:

I do not know.  When I say "I am not opposed to", I mean just that. 

I may consider it a bad mode of operation, and I may hesitate to encourage people to use it as their default. But I do not feel strongly enough to veto it---as long as it is a rope you need to explicitly ask for to hang yourself with, I think it is Ok if we allowed such an option.

It is not my itch to scratch, and I do not keep track.

Did you submit a patch that implements the new feature cleanly?

Junio C Hamano <gitster@pobox.com> wrote:

Thanks for the summary.

Nope. I'm just barely emerging from newbie status, so I'm probably a ways away from implementing it.

Kevin

Hi,

On Thu, 5 Feb 2009, layer wrote:

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).

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

Ciao, Dscho