Recently we had a user in #svn who somehow managed to create a
copy that could not be committed because of out-of-dateness errors.
I am not exactly sure what the real cause of the problem was.
It could be worked around by using a URL as copy source. So it
is likely that mixed-revisionnes somehow interfered the commit.
It was pointed out that novice users may not realise that they
might be copying mixed-revision trees if they run
svn copy DIR1 DIR2
in their working copy. Of course, mixed-revisions are explained
in chapter 2 of the book and should be considered basic knowledge.
But because mixed-revisionness is hard to notice (nothing except
'svn info' shows it), users often simply forget about it.
We added the --allow-mixed-revisions option to 'svn merge' in 1.7.
Would it make sense to make 'svn copy' require this option if the
copy source is a mixed-rev WC subtree, in 1.8?
This would make sure that WC->{WC,URL} copies produce, by default,
the same result as URL->URL copies (modulo local mods in the WC).
