Re: patch: do not emit trailing blanks in context header

[Jim Meyering]

Paolo Bonzini <address@hidden> wrote:
>> Do you mean that you *can* fix it for diff -u ?
>> That'd be nice.
>>
>>   $ diff -u <(printf 'a\n\nb\n') <(printf 'a\n\nc\n')|grep -l ' $'
>>   (standard input)
>>
> Would old `patch' programs accept the output?  If not, I find it an
> extremely bad idea.

Hi Paolo,

I have not done any exhaustive study by any means, but patch-2.5.9 works
just fine without at least some of those added trailing blanks in diff -u
output.

You can see that it works using the example above.  Give patch
the diff -u output with the sole trailing blank removed:

  $ printf 'a\n\nb\n' > 1
  $ diff -u <(printf 'a\n\nb\n') <(printf 'a\n\nc\n')|sed 's/ $//'|patch 1 -
  patching file 1

Of course, we're not talking about trailing blanks added or changed due
to inputs with differences (or in context).  Rather, we're talking
about the fact that diff -u adds a space on any output line
what would otherwise be blank.