Issue #4007 - Diff constructs invalid paths for a git-format property diff

[Julian Foad <ju...@wandisco.com>]

This bug is present in 1.7.0-RC2 and crashes with assertions enabled or
displays invalid paths with assertions disabled.

Actual input and output, using a release build (assertions disabled):
[[[
$ svn1 --version -q
1.7.0-rc2

$ svn1 diff --git -c1141953 /home/julianfoad/src/subversion-d/subversion/include/private/svn_io_private.h
Index: /home/julianfoad/src/subversion-d/subversion/include/private/svn_io_private.h
===================================================================
diff --git a/subversion/trunk/subversion/include/private/svn_io_private.h//home/julianfoad/src/subversion-d/subversion/include/private/svn_io_private.h b/subversion/trunk/subversion/include/private/svn_io_private.h//home/julianfoad/src/subversion-d/subversion/include/private/svn_io_private.h
--- a/subversion/trunk/subversion/include/private/svn_io_private.h//home/julianfoad/src/subversion-d/subversion/include/private/svn_io_private.h	(revision 1141952)
+++ b/subversion/trunk/subversion/include/private/svn_io_private.h//home/julianfoad/src/subversion-d/subversion/include/private/svn_io_private.h	(revision 1141953)

Property changes on: subversion/trunk/subversion/include/private/svn_io_private.h//home/julianfoad/src/subversion-d/subversion/include/private/svn_io_private.h
___________________________________________________________________
Added: svn:eol-style
## -0,0 +1 ##
+native
]]]

Expected output: the four paths shown on the three lines starting from
"diff --git" should not have "...private.h//home/julian..." in them.
Instead I believe they should be repository-relative paths appended to
an "a" or "b" prefix.

If I specify a relative path on the command line instead of an absolute
path, then the assertion is not triggered (in a build with assertions
enabled) but the paths are wrongly constructed.

- Julian