trouble with mixed-EOL files with svn:eol-style=native

Occasionally somebody manages to create a Subversion repository in which some revisions of a file contain a mixture of end-of-line styles, but svn:eol-style=native. This requests Subversion to perform end-of-line character translation on checkout, which it will refuse to do in the presence of mixed EOL styles. For instance:

  $ svn cat -r998 svn://svn.tartarus.org/sgt/putty/x11fwd.c >/dev/null
  svn: Inconsistent line ending style

This broke the putty import:

  http://launchpadlibrarian.net/16631291/putty-trunk-log.txt

While Subversion itself doesn't make it easy to do this, it is possible to end up in this situation due to a conversion from CVS, as indeed is the case for putty. We should somehow arrange to be able to import such branches anyway.

There are a couple of possibilities, which mostly look like they would involve reimplementing svn_client_cat2. We could ignore the svn:eol-style property on anything that raises this exception, or we could arrange to set the repair flag for svn_subst_stream_translated. I think the former will produce a mixed-EOL output file while the latter will just blat all the newlines in the file into the native format.

From what I can tell, Subversion's pedantry here is in order to avoid corrupting binary files that mistakenly have svn:eol-style=native set. Yes, those will end up corrupted anyway if you check them out on a platform with a different EOL style, but at least you can repair them on the original platform, which is probably the common case anyway. However, I think this is less of an issue for code imports. Not only is it perhaps more likely that people will be checking out the branch on a different platform, but also the original branch remains available and in extremis one could always retrieve the binary file from there. In most cases, I suspect that later revisions of the file will have had their EOL inconsistency repaired or the svn:eol-style property removed, as appropriate; in the case at hand, 'svn cat svn://svn.tartarus.org/sgt/putty/x11fwd.c' (the current revision) succeeds.