Consider providing an easier way to load remote files with Jsonnet

[jbrunton]

jsonnet-bundler may be heavyweight for a lot of cases. perhaps allow remote urls in libs lists, and download automatically.

[jbrunton]

Perhaps introduce a .gflowslib extension. Example:

# https://example.com/my-lib.gflowslib
{
  "files": [
    "foo.yml",
    "bar/baz.yml"
  ]
} 

This would add the files listed to the build library. If remote, it would download local versions.

Would be useful for ytt too.

[jbrunton]

Possible semantics:

1. During execution, files are downloaded locally to a temp directory, maintaining same directory structure.
2. File paths must be relative to parent gflowslib file and contained within the same directory.
3. The temp directory is added to config.libs.

[jbrunton]

It would be helpful to support both library files and workflows. Something like this:

# https://example.com/my-lib.gflowslib
{
  "libs": [
    "my-lib.yml",
    "other/lib.yml"
  ],
  "workflows": [
    "my-workflow.yml"
  ]
} 

..altho this will need to consider the differences between how workflows are identified by ytt and jsonnet engines.

ytt example:

  "libs": [
    "my-lib.yml"
  ],
  "workflows": [
    "my-workflow/config.yml",
    "my-workflow/foo.yml",
    "bar.yml"
  ]

Above example would generate a workflow called "my-workflow", and would ignore "bar.yml" (perhaps offering a warning).

jsonnet example:

  "libs": [
    "my-lib.libsonnet"
  ],
  "workflows": [
    "my-workflow.jsonnet"
  ]