[Cc to Stefan Monnier, who introduced -d in GNU Emacs in 2007]
On 2024-08-19 17:17:27 -0700, Paul Eggert wrote:
> On 2024-08-19 16:55, Vincent Lefevre wrote:
> > When opening a .diff file, GNU Emacs runs "diff -ad" on 2 files
> > it has built (I suppose that the reason is to get a word diff),
> > and this can be very slow
>
> That's inherent to the algorithm, no? I don't know of any faster algorithm,
> if you really want minimal output. If you know of one, please let us know.
>
> A simple workaround would be for GNU Emacs to not use the -d (--minimal)
> option.
Perhaps not possible. In the Emacs code (in lisp/vc/smerge-mode.el),
I could find:
(let ((coding-system-for-read 'utf-8-emacs))
(call-process diff-command nil t nil
(if (and smerge-refine-ignore-whitespace
(not smerge-refine-weight-hack))
;; Pass -a so diff treats it as a text file even
;; if it contains \0 and such.
;; Pass -d so as to get the smallest change, but
;; also and more importantly because otherwise it
;; may happen that diff doesn't behave like
;; smerge-refine-weight-hack expects it to.
;; See
https://lists.gnu.org/r/emacs-devel/2007-11/msg00401.html
"-awd" "-ad")
file1 file2))
I suppose that this is the code that is called, as I couldn't
find another occurrence of -ad. So there is a reference to
https://lists.gnu.org/r/emacs-devel/2007-11/msg00401.html
(that was with diff (GNU diffutils) 2.8.1) and the latest message
(about the use of -d, in particular):
https://lists.gnu.org/r/emacs-devel/2007-11/msg00522.html
--
Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
