- Move the population of the feed's entries into a new function, to make
`BuildFeed` easier to understand/separate concerns/implementation details
- Use `sort+compact` instead of `compact+sort` to remove duplicates
- Change `if !a { a = } if !a {a = }` constructs into `if !a { a = ; if !a {a = }}`.
This reduce the number of comparisons, but also improves a tad the
control-flow readability.
