Stay updated with changes to related compilation targets of same package (e.g. src & test)

[DanBurton]

Thank you for your hard work! I have a request.

When I have multiple buffers open with different compilation targets of the same package in each buffer, I would like it if, for example, updating a src module will propagate the changes to another buffer open on the test module that imports that src module. What currently happens is that I need to restart the HLS, or restart my editor (emacs), in order for HLS to pick up the changes to the upstream component in the test module buffer.

[theGhostJW]

To reproduce:

1. open the following in HLS: https://github.com/theGhostJW/pyrethrum/releases/tag/346_Repro_1
2. evaluate (using Eval lens) -- >>> "Hello " <> salutation in DemoTest.hs
3. will evaluate to "Hello World"
4. change salutation in Demo.hs
5. refresh -- >>> "Hello " <> salutation in DemoTest.hs
6. the eval does not reflect the change in the Demo module

[michaelpj]

I think this should be fixed by the proper multi-home-unit support.