Add 'dis' component

This commit adds a new 'dis' component to the distillery that serves a
list of all known instances for the moment.

core/params.go

@@ -0,0 +1,31 @@
+package core
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// Params are used to initialize the excutable.
+type Params struct {
+	ConfigPath string // ConfigPath is the path to the configuration file for the distillery
+}
+
+// ParamsFromEnv creates a new set of parameters from the environment.
+// Uses [ReadBaseDirectory] or falls back to [BaseDirectoryDefault].
+func ParamsFromEnv() (params Params, err error) {
+
+	// try to read the base directory!
+	value, err := ReadBaseDirectory()
+	switch {
+	case os.IsNotExist(err):
+		params.ConfigPath = BaseDirectoryDefault
+	case err == nil:
+		params.ConfigPath = value
+	default:
+		return params, err
+	}
+
+	// and add the configuration file name to it!
+	params.ConfigPath = filepath.Join(params.ConfigPath, ConfigFile)
+	return params, nil
+}