clone: simplifying dest repo creation
since creating a repo raises an exception if the repo already
exists, there's no need to try to create one.
add some test for repo creation when the destination exists
port:4:export
port:4:vaportight
port:4:import/export
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port:3:4:+:eggs:import/export
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port:4:import/export
% follow
port:0:import
port2:6:4:+:eggs:deport
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port:1:2:+:eggs:export
port:0:1:+:eggs:import