datasource: Move datasources into their own packages.

datasource/file/file.go

@@ -0,0 +1,39 @@
+package file
+
+import (
+	"io/ioutil"
+	"os"
+)
+
+type localFile struct {
+	path string
+}
+
+func NewDatasource(path string) *localFile {
+	return &localFile{path}
+}
+
+func (f *localFile) IsAvailable() bool {
+	_, err := os.Stat(f.path)
+	return !os.IsNotExist(err)
+}
+
+func (f *localFile) AvailabilityChanges() bool {
+	return true
+}
+
+func (f *localFile) ConfigRoot() string {
+	return ""
+}
+
+func (f *localFile) FetchMetadata() ([]byte, error) {
+	return []byte{}, nil
+}
+
+func (f *localFile) FetchUserdata() ([]byte, error) {
+	return ioutil.ReadFile(f.path)
+}
+
+func (f *localFile) Type() string {
+	return "local-file"
+}