5671_20090414.patch: If src fs does not support file checksum, it may throw a FileNotFoundException. In such case, we should return true.

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Tested manually, no new tests added.

Based on the documentation of the method FileSystem.getFileChecksum(), not supporting checksum is indicated by null return and not by throwing exception. So should we ensure the classes extending FileSystem honor this?

> In DistCp.sameFile(..), if src FileSystem does not support file checksum, it should return true.

More details of the problem:
Some previous versions HftpFileSystem do not support file checksum and throw FileNotFoundException since the request url is not found. In such case, DistCp.sameFile(..) should return true.

5671_20090415.patch: rewritten the comments, no code changes.

+1

I committed this. Thanks, Nicholas

Thanks Nicholas, Chris, Suresh!

Since this is sort of a regression for 0.19, can we also commit it to 0.19.* and 0.20.1 ?
(-update option won't work without this patch when pulling from 0.18 cluster or earlier versions)

Really appreciate it if we can commit it to 0.19 and earlier releases.

Integrated in Hadoop-trunk #811 (See http://hudson.zones.apache.org/hudson/job/Hadoop-trunk/811/)

Committed to 0.19.2 and 0.20.1 as well

Integrated in Hadoop-trunk #815 (See http://hudson.zones.apache.org/hudson/job/Hadoop-trunk/815/)
Move from 0.21 to 0.19.2