Allow licensed apps to share caches

[jonabc]

This adds in an option for users to configure apps that share a cache path, and works both for explicitly declared apps as well as apps defined by glob patterns.

Source paths given with glob patterns need special handling to not append the app folder name to an explicitly specified cache path. In this scenario users can add a shared_config: true configuration value to the same configuration level as the glob source path.

From the docs update:

Sharing caches between apps

Dependency caches can be shared between apps by setting the same cache path on each app.

apps:
  - source_path: "path/to/app1"
    cache_path: ".licenses/apps"
  - source_path: "path/to/app2"
    cache_path: ".licenses/apps"

When using a source path with a glob pattern, the apps created from the glob pattern can share a dependency by setting an explicit cache path and setting shared_cache to true.

source_path: "path/to/apps/*"
cache_path: ".licenses/apps"
shared_cache: true

/cc @zarenner this should allow you to cache all dependencies to the same folder. Does this seem like a viable solution?

[zarenner]

Tested it against my repo, looks good! Thanks!

[zarenner]

Minor nit:
I'm guessing this might have been intentional, but I would have expected the syntax

cache_path: ".licenses"
shared_cache: true
apps:
  - source_path:  foo
  - source_path:  bar

to share .licenses and it doesn't (have to individually specify cache_path for each app)?

[jonabc]

I'm guessing this might have been intentional, but I would have expected the syntax

🤔 it's intentional that the shared_cache value isn't inherited for cases where the cache_path is set at the same level as an app. So in the following scenario the setting wouldn't apply to cache_path: .licenses/foo.

shared_cache: true
apps:
  - source_path: foo/cmd/*
     cache_path: .licenses/foo
  - source_path: bar

Sharing a cache is potentially dangerous and should be a reasoned decision based on user needs, so the intention is that it only applies to cache_paths defined at the same level. I think what you found is a bug - I'll make that update, thanks!