While merging multiple subversion repositories with svn-merge-repos.pl, I got a rather strange error:
svnadmin: File not found: transaction 'yyy', path 'xxx'
The last command issued by the perl script was
svnadmin dump --revision 86 --incremental '/srv/svn/foobar' | svndumpfilter include '/projects/foobar' | svnadmin load --parent-dir 'foobar' '/srv/svn/total'
Apparently, the error is caused by the directory selection for one repository. When selecting a subtree of a repository, the parent folder has to be imported, as well. Just change the call to svn-merge-repos.pl accordingly and you're fine.