Re: ediff maximum line length?

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I am looking for something that can compare two files, so that I can
> launch Emacs as my diff tool, e.g. from Perforce, Subversion, etc.  I
> don't know if diff-mode can compare two files instead of a buffer and
> its file.

diff-mode is not a replacement for ediff in that it only helps you read
contextual diffs (i.e. the output of `diff' or other tools that output
in the same format).
So, if you do

  exec emacs --eval "(diff \"$1\" \"$2\")"

the resulting *diff* buffer will be in diff-mode.
  
> That's why I used ediff.  (Another reason is that I know its
> key bindings from vc, but that's not something I can't live without.)

From VC, C-x v = will give you a diff that's displayed in diff-mode.

For some uses, this is much better than ediff, but for others ediff is
more appropriate.  I've gotten so used to reading diffs that I don't use
ediff nearly as much as diff-mode, tho.

> Is it possible to use diff-mode for the same sort of comparison?

Yes, see above.


        Stefan


PS: For 3-way "diffs", smerge-mode provides a similar alternative to
ediff3, and also supports highlighting of fine diffs.
And there's probably a way to get diff3-style output from `diff', so as
to use smerge-mode for 2-way comparisons.