App improvement mega issue

[KristofferC]

Things to fix/improve:

Functionality

• Add Apps.instantiate
• Add Apps.update
• Allow specifying a subfolder in package with a project [+ manifest] with an app
• Allow submodules with @main as apps

Display

• Improve output of Apps.status()
• Move away from using @info and use the same formatting as Pkg does elsewhere

Questions

• PATH handling, make juliaup add .julia/bin to path?
• How to make juliaup not GC versions used by apps

[nilshg]

As discussed on Slack, I would propose changing the info output to

Info: package Runic installed the following app(s): runic

(maybe print app singular if only one is installed and plural otherwise, assuming that's easy to determine)

[ericphanson]

some observations trying out the apps feature:

• I think load path or project influences compat for app add when it seems like it should not
  • I worked around this in my installation instructions for SearchablePDFs.jl by writing JULIA_LOAD_PATH="@:@stdlib" julia +nightly --startup-file=no -e 'using Pkg; Pkg.activate(temp=true); Pkg.Apps.add(url="https://github.com/ericphanson/SearchablePDFs.jl")'. Pretty long!
• updating an app should probably regenerate the project/manifest from scratch (delete them), since otherwise there can be issues with the manifest
• similarly, I did app add ... then app dev ... and the generated manifest still was that of app add instead of updating to the format used with dev
• app rm does not remove the generated environment, I believe it should
• if an app fails to precompile when installed, the errors are not clear but it seems to retry like 3 times. I think this is because it's the auto-precompile on installation, maybe it should set some flags or something for this case when it's not a regular library dependency