The most annoying subversion error message:
$ svn up ... svn: Won't delete locally modified directory 'foo/bar' svn: Left locally modified or unversioned files
This happens when a subdirectory of 'foo/bar' is removed from the upstream repository, and subversion tries and fails to remove ir locally -- fails because it finds some some files that are listed in svn:ignore (e.g. editor backup files, compiled object files, compiled Python modules).
Now you have to figure out which subdirectory of 'foo/bar' subversion wants
to remove. Then you have to manually remove junk files from it. Then you
have to repeatedly try various combinations of svn up and
svn cleanup until Subversion finally agrees to continue the
interrupted svn up operation.
Please, Subversion folks -- if you cannot delete a directory because it
contains just junk files (those ignored in the output of svn
status), just print a meaningful warning message (and name the correct
directory rather than its parent!) and continue with the update.
Update: It seems to be fixed in Subversion 1.1. Unfortunately Subversion 1.1 is not in Debian.