Get last usns from a filepath (#1029)

* feat: getting last usns from a filepath

* Fix typo

---------

Co-authored-by: Nicolas Bender <nicolas.bender@sap.com>

Author: pacostas

actions/stack/get-usns/action.yml

@@ -17,6 +17,9 @@ inputs:
     description: 'JSON array of last known USNs'
     required: false
     default: '[]'
+  last_usns_filepath:
+    description: 'Similar to last_usns, but instead of pointing into a variable, it points to a file'
+    required: false
   packages:
     description: 'JSON array of stack package names'
     required: false
@@ -39,6 +42,8 @@ runs:
   - "${{ inputs.feed_url }}"
   - "--last-usns"
   - "${{ inputs.last_usns }}"
+  - "--last-usns-filepath"
+  - "${{ inputs.last_usns_filepath }}"
   - "--packages"
   - "${{ inputs.packages }}"
   - "--packages-filepath"

actions/stack/get-usns/entrypoint/main.go

@@ -48,6 +48,7 @@ func main() {
 	var config struct {
 		Distro               string
 		LastUSNsJSON         string
+		LastUSNsJSONFilepath string
 		Output               string
 		PackagesJSON         string
 		PackagesJSONFilepath string
@@ -59,6 +60,10 @@ func main() {
 		"last-usns",
 		"",
 		"JSON array of last known USNs")
+	flag.StringVar(&config.LastUSNsJSONFilepath,
+		"last-usns-filepath",
+		"",
+		"Filepath that points to the JSON array of last known USNs")
 	flag.StringVar(&config.RSSURL,
 		"feed-url",
 		"https://ubuntu.com/security/notices/rss.xml",
@@ -108,6 +113,19 @@ func main() {
 		log.Fatal(err)
 	}
 
+	if config.LastUSNsJSONFilepath != "" {
+
+		lastUSNsFilepath, err := os.ReadFile(config.LastUSNsJSONFilepath)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		err = json.Unmarshal(lastUSNsFilepath, &lastUSNs)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+
 	var packages []string
 	err = json.Unmarshal([]byte(config.PackagesJSON), &packages)
 	if err != nil {