Turns out that it is actually a bug and that there is a workaround, as Stefan Küng points out:
But regardless of that, are you saying that if I create the following folders and commit them to the ^/_all/ folder, and then add the respective externals to them (instead of to the _all/ folder directly), it would work?
Create this folder in SVN... | ...and attach this one as an external
^/_all/project1/trunk | ^/project1/trunk^/_all/groupA/subgroup1/project2/trunk | ^/groupA/subgroup1/project2/trunk^/_all/project3 | ^/project3Not quite:
^/_all/project1 | ^/project1/trunk^/_all/groupA/subgroup1/project2 | ^/groupA/subgroup1/project2/trunk^/_all/ | ^/project3