On a per-request basis. Allows hiding/showing at multiple granularities
* everything
* module
* API by name
* keywords (by uid or all of them)
* literals (by uid or all of them)
With more specific rules overriding less specific ones (so you can hide
everything and then selectively show certain API for example).
rdar://24170060
At some point I want to propose a revised model for exports, but for now
just mark that support for '@exported' is still experimental and subject
to change. (Thanks, Max.)
The code goes into its own sub-tree under 'tools' but tests go under 'test',
so that running 'check-swift' will also run all the SourceKit tests.
SourceKit is disabled on non-darwin platforms.
