I've converted the GCC svn repository to a hg repository as described in
Issue2013.  After cloning the trunk from the hg repository with

$ hg clone -rdefault ../repo dist

I ultimately noticed (after some bug hunting) that the conversion had
resurrected a file that had been renamed in svn:

gcc/testsuite/gcc.dg/20021205-1.c

(I've now checked this and it seems to be the only one.)  This is very
unfortunate if you cannot rely on the hg mirror being correct.