Re: [PATCH v2] make diff --color-words customizable

[Thomas Rast <trast@student.ethz.ch>]

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Johannes Schindelin wrote:
> BTW I did not really think about the issue you raised about the newlines, 
> as I seemed to remember that the idea was to substitute all non-word 
> characters with newlines, so that the offsets in the substituted text are 
> the same as in the original text.

Ok, so here's a very simple example: Suppose you have the word regex
'x+|y+' and compare these two lines:

A: xxyyxy
B: xyxyy

There are *no* non-word characters between consecutive words in this
case, so you *cannot* replace them with newlines.  You cannot replace
some word character either, as should be obvious from the case of
one-letter words, as you would lose actual content.  My counterexample
to your illustration patch exploited a similar border case: suppose
you decide to overwrite the first (instead of last) character of each
word, then you won't be able to tell "foo" from "\noo" in the input.

Unfortunately the space adjustement makes things even worse.  The
existing method has the side-effect that it only inserts a single
newline between words separated by exactly one space, which runs them
together in the resulting line diff, for example

A: foo bar
B: baz quux

would result in

  -foo
  -bar
  +baz
  +quux

instead of (as my original attempts did) the arguably more correct,
but less readable

  -foo
  +bar
    
  -baz
  +quux

where the middle line is a context line for the space.  So in addition
to the word-ending adjustments for the inserted newlines, I also have
to track the status of the space right after the word.

> So I still find your patch way too large

I can't think of a simpler way to do it, and yours unfortunately
doesn't work.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch



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