Currently, existing distfiles digests are automatically assumed when local copies of the distfiles are not available in $DISTDIR. The problem with behavior is that if the upstream distfiles change identity while keeping the same name, the user may be forced to manually remove both the Manifest and files/digest-$PF file in order to force the fetch and/or digest to occur correctly. I propose that a --force option to be supported by the ebuild command in order to automate this process. The --force option will simply remove the digests associated with the current ebuild (from both the Manifest and files/digest-$PF files) so that fetch and/or digest will ignore the previously existing distfiles digests.
This is fixed in svn r4041.
This has been released in 2.1.1_pre4.
This is in svn r4060 for 2.1-r2.
