fix: support downgrade/upgrade for unknown versions

cli/app/upgrade.go

@@ -54,10 +54,6 @@ data beforehand - see "abra app backup <app>" for more.
 			logrus.Fatal(err)
 		}
 
-		if deployedVersion == "" {
-			logrus.Fatalf("failed to determine version of deployed '%s'", app.Name)
-		}
-
 		if !isDeployed {
 			logrus.Fatalf("'%s' is not deployed?", app.Name)
 		}
@@ -67,23 +63,35 @@ data beforehand - see "abra app backup <app>" for more.
 			logrus.Fatal(err)
 		}
 
-		var availableUpgrades []string
-		for _, version := range versions {
-			parsedDeployedVersion, err := tagcmp.Parse(deployedVersion)
-			if err != nil {
-				logrus.Fatal(err)
-			}
-			parsedVersion, err := tagcmp.Parse(version)
-			if err != nil {
-				logrus.Fatal(err)
-			}
-			if parsedVersion.IsGreaterThan(parsedDeployedVersion) {
-				availableUpgrades = append(availableUpgrades, version)
-			}
+		if len(versions) == 0 {
+			logrus.Fatalf("no versions available '%s' in recipe catalogue?", app.Type)
 		}
 
-		if len(availableUpgrades) == 0 {
-			logrus.Fatal("no available upgrades, you're on latest")
+		var availableUpgrades []string
+		if deployedVersion == "" {
+			deployedVersion = "unknown"
+			availableUpgrades = versions
+			logrus.Warnf("failed to determine version of deployed '%s'", app.Name)
+		}
+
+		if deployedVersion != "unknown" {
+			for _, version := range versions {
+				parsedDeployedVersion, err := tagcmp.Parse(deployedVersion)
+				if err != nil {
+					logrus.Fatal(err)
+				}
+				parsedVersion, err := tagcmp.Parse(version)
+				if err != nil {
+					logrus.Fatal(err)
+				}
+				if parsedVersion.IsGreaterThan(parsedDeployedVersion) {
+					availableUpgrades = append(availableUpgrades, version)
+				}
+			}
+
+			if len(availableUpgrades) == 0 {
+				logrus.Fatal("no available upgrades, you're on latest")
+			}
 		}
 
 		var chosenUpgrade string