[Bug 862750] Re: svn diff refuses to pass no arguments to external diff program

[Martin Weis]

If you use echo as command you see the commandline:

$ svn -r1 diff --diff-cmd echo README.txt 
Index: README.txt
===================================================================
-u -L README.txt	(revision 1) -L README.txt	(working copy) .svn/tmp/tempfile.tmp README.txt

and as I aready stumbled upon this problem recently on a Macintosh, a look into the svn book reveals, that always GNU diff options are used:
http://svnbook.red-bean.com/en/1.5/svn.advanced.externaldifftools.html

Although I dont know, why this worked until now. Maybe meld changed its
behaviour?

A wrapper script as in the link can help. This script works for me here,
save meldsvn.py in $PATH


** Attachment added: "meldsvn.py wrapper script"
   https://bugs.launchpad.net/ubuntu/+source/subversion/+bug/862750/+attachment/2536652/+files/meldsvn.py

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https://bugs.launchpad.net/bugs/862750

Title:
  svn diff refuses to pass no arguments to external diff program

Status in “subversion” package in Ubuntu:
  Confirmed

Bug description:
  I like to use meld as an external diff program which svn diff.

  For instance, I used to be able to run
      svn diff --diff-cmd meld
  and everything would just work.

  Now I get the following error:

  
  ed at ed-Ubu64:~/f11/trunk$ svn diff --diff-cmd meld
  Index: ocaml/traces.ml
  ===================================================================
  Xlib:  extension "RANDR" missing on display ":0.0".
  Usage: 
    meld                        Start with an empty window
    meld <file|dir>             Start a version control comparison
    meld <file> <file> [<file>] Start a 2- or 3-way file comparison
    meld <dir> <dir> [<dir>]    Start a 2- or 3-way directory comparison
    meld <file> <dir>           Start a comparison between file and dir/file

  meld: error: no such option: -u
  svn: 'meld' returned 2

  svn is passing -u to meld.  That's okay, this is documented.  From svn
  help:

  
    -x [--extensions] ARG    : Default: '-u'. When Subversion is invoking an
                               external diff program, ARG is simply passed along
                               to the program. But when Subversion is using its
                               default internal diff implementation, or when
                               Subversion is displaying blame annotations, ARG
                               could be any of the following:

  So, if I run svn diff --diff-cmd meld -x "" it should not pass -u to
  meld.  Let's try it:

  
  Index: ocaml/traces.ml
  ===================================================================
  Xlib:  extension "RANDR" missing on display ":0.0".
  Usage: 
    meld                        Start with an empty window
    meld <file|dir>             Start a version control comparison
    meld <file> <file> [<file>] Start a 2- or 3-way file comparison
    meld <dir> <dir> [<dir>]    Start a 2- or 3-way directory comparison
    meld <file> <dir>           Start a comparison between file and dir/file

  meld: error: no such option: -u
  svn: 'meld' returned 2

  Nope, still passes -u.  Using a non-empty string works:
      svn diff -x "-L hello" --diff-cmd meld

  ProblemType: Bug
  DistroRelease: Ubuntu 11.04
  Package: subversion 1.6.12dfsg-4ubuntu2.1
  ProcVersionSignature: Ubuntu 2.6.38-11.50-generic 2.6.38.8
  Uname: Linux 2.6.38-11-generic x86_64
  NonfreeKernelModules: nvidia wl
  Architecture: amd64
  Date: Thu Sep 29 16:30:04 2011
  InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
  ProcEnviron:
   LANGUAGE=en_US:en
   PATH=(custom, user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: subversion
  UpgradeStatus: No upgrade log present (probably fresh install)

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