Remove some unnecessary parsing and copying (#1446)
Remove some unnecessary parsing and copying (#1446)

PackageEntry is more or less private API; we can assume it will be called with valid URLs.

Parsing URLs unnecessary adds quite a bit of overhead for large manifests.
quiltdata/quilt-compiler,quiltdata/quilt-compiler,quiltdata/quilt-compiler,quiltdata/quilt,quiltdata/quilt-compiler,quiltdata/quilt,quiltdata/quilt,quiltdata/quilt,quiltdata/quilt