At the moment, packages which originate from a package index other than the requested one are overwritten. While not strictly wrong, this is often undesirable for the WebKit project, where packages from different indexes my share an install location.
Created attachment 406853 [details]
Very willing to change the terminology here, "forgein" just felt like the right term for "something on disk that originates from a package index other than the index the program specified"
Committed r265880: <https://trac.webkit.org/changeset/265880>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 406853 [details].