ra: Rework export of non link file with svn:special property set
The fix introduced in 58a07c67 to ensure reconstruction of non link binary file with svn:special property set will be the same as an export operation was not generic enough to handle all possible cases that can be found in the wild.
So rework it by explicitely exporting that specific file with a subversion client when it is needed.
Related to #3695
Depends on !86 (closed)
Migrated from D6722 (view on Phabricator)