Description:
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copying a large file to itself result in a 64ko truncated file

Reproduce code:
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$somepath = [path_to_a_file];
copy($somepath, $somepath);

Expected result:
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leave somefile unaltered

Actual result:
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on Debian 64-bit (not on OS X Leopard), any file > 64ko copied to itself result in a 64ko file.
i suppose that's because it copies files by 64ko blocks and writes block per block so after the first block copy, the source is 64ko length.
as it can result in data loss and copying a file to itself should do nothing, i propose to raise a warning and do nothing when copy has the same path for source and dest.