Copy backend does not detect file conflicts

[Celso Providelo]

The current copy infrastructure checks for version conflicts but does not catch file content clashes.

Since DSCs and DIFFs and native TARBALLs are unique across source versions as binary files, they are indirectly checked by operations on versions.

This problem affects specifically ORIG TARBALLs files, because they are allowed to be different in different archives, but if the source is copied to another PPA a clash may happen and the publisher will refuse to override the previously published in the destination pool/.

We should check for ORIG filename/content clashes and deny the copy if it's the case.

This problem seems to occur more frequently in daily-build/snapshots PPAs. It might be worth to investigate how to improve `ppa-scripts` [1] to avoid this scenario.

[1] ppa-script is a tool widely used for daily-builds in PPAs, https://code.edge.launchpad.net/~fta/+junk/ppa-scripts

[William Grant (wgrant)]

Note that COMPONENT_ORIG files now need to be checked too -- why not just check all of them to be safe?

[Ursula Junque (ursinha)]

Fixed in stable r10701 <http://bazaar.launchpad.net/~launchpad-pqm/launchpad/stable/revision/10701>

[Steve Kowalik (stevenk)]

This branch failed QA on dogfood. :-(

I have prepared another branch which sorts out the error.

[Ursula Junque (ursinha)]

Fixed in stable r10807 <http://bazaar.launchpad.net/~launchpad-pqm/launchpad/stable/revision/10807>

[Steve Kowalik (stevenk)]

I have QA'd this on dogfood by creating two fresh PPAs, and crafting uploads to the two of them with conflicting orig tarballs. Trying to copy from one PPA to the other resulted in the following error:

The following source cannot be copied:
    * nothing 2.4-3.2 in karmic (nothing_2.4.orig.tar.gz already exists in destination archive with different contents.)