Re: 23.0.50; vc: missing done in progress message

[Thien-Thi Nguyen <ttn@gnuvola.org>]

() Glenn Morris <rgm@gnu.org>
() Wed, 30 Jan 2008 19:56:46 -0500

   [recipe] and message: "Running svn diff filename...OK = 0"

   Anyway, the only point I'm trying to make is that "OK = 0" is useless
   as a status message, because it could mean anything:

   1) The diff command completed succesfully (exit status 0 in a shell
   command sense). There may or may not be differences.

   2) The diff command failed (0 is false in a C sense).

   3) There were no differences (the GNU diff exit status convention).

Now I'm confused.  Before, i was moderately sure that the
convention (case 3) was universal.  Here is a quick survey of a
the documentation for the "diff" functionality for a subset of the
backends:

* RCS rcsdiff(1)
  Exit status is 0 for no differences during any comparison, 1 for
  some differences, 2 for trouble.

* CVS "(cvs) Exit status"
  It will return a successful status if it found no differences,
  or a failure status if there were differences or if there was an
  error.  Because this behavior provides no good way to detect
  errors, in the future it is possible that `cvs diff' will be
  changed to behave like the other CVS commands.

* Git git-diff(1)
  --exit-code
  Make the program exit with codes similar to diff(1).  That is,
  it exits with 1 if there were differences and 0 means no
  differences.
  [An option, but one that vc-git.el uses unconditionally. --ttn]

* SVN "svn diff help" output
  [no mention of exit value]

* HG http://www.selenic.com/mercurial/hg.1.html
  [no mention of exit value]

* Bzr http://doc.bazaar-vcs.org/bzr.dev/en/user-reference/bzr_man.html#diff
  Exit values:
  1 - changed 2 - unrepresentable changes 3 - error 0 - no change

I suppose SVN follows CVS, and HG and others follow the rest, and
would be very surprised to learn of a backend that deliberately
(by design) did not follow this convention.

   Something like "...done" or "...failed" would be a lot clearer IMO.

Agreed.  Up-thread, i mentioned all the branches in the vc-diff
code path.  I think a good approach is to coalesce all paths to
end up in vc-diff-finish and add the human-friendly notification
there.  If no one beats me to it, i'll look into it in a week.

thi