Make error messages in update information less vague.

internal/helpers/updateinformation.go

@@ -58,27 +58,27 @@ func NewUpdateInformationFromString(updateinformation string) (UpdateInformation
 	ui.transportmechanism = parts[0]
 	if ui.transportmechanism == "zsync" {
 		if len(parts) < 2 {
-			return ui, errors.New("Too short")
+			return ui, errors.New("Update information isn't valid")
 		}
 		ui.fileurl = parts[1]
 	} else if ui.transportmechanism == "gh-releases-zsync" {
 		if len(parts) < 5 {
-			return ui, errors.New("Too short")
+			return ui, errors.New("Update information isn't valid")
 		}
 		ui.username = parts[1]
 		ui.repository = parts[2]
 		ui.releasename = parts[3]
 		ui.filename = parts[4]
 	} else if ui.transportmechanism == "bintray-zsync" {
 		if len(parts) < 5 {
-			return ui, errors.New("Too short")
+			return ui, errors.New("Update information isn't valid")
 		}
 		ui.username = parts[1]
 		ui.repository = parts[2]
 		ui.packagename = parts[3]
 		ui.filename = parts[4] // a.k.a. "zsync path"
 	} else {
-		return ui, errors.New("This transport mechanism is not yet implemented")
+		return ui, errors.New("The transport mechanism in update information is not yet implemented")
 	}
 	return ui, nil
 }
@@ -89,7 +89,7 @@ func NewUpdateInformationFromString(updateinformation string) (UpdateInformation
 func ValidateUpdateInformation(updateinformation string) error {
 	parts := strings.Split(updateinformation, "|")
 	if len(parts) < 2 {
-		return errors.New("Too short")
+		return errors.New("Update information isn't valid")
 	}
 	// Check for allowed transport mechanisms,
 	// https://github.com/AppImage/AppImageSpec/blob/master/draft.md#update-information
@@ -101,21 +101,21 @@ func ValidateUpdateInformation(updateinformation string) error {
 		}
 	}
 	if detectedTm == "" {
-		return errors.New("Invalid transport mechanism")
+		return errors.New("Invalid transport mechanism in update information")
 	}
 
 	// Currently updateinformation needs to end in "zsync" for all transport mechanisms,
 	// although this might change in the future
 	// Note that it is allowable to have something like "some.zsync?foo=bar", which is why we parse it as an URL
 	u, err := url.Parse(parts[len(parts)-1])
 	if err != nil {
-		return errors.New("Cannot parse URL")
+		return errors.New("Cannot parse URL in update information")
 	}
 	if detectedTm == "zsync" && u.Scheme == "" { // FIXME: This apparently never triggers, why?
-		return errors.New("Scheme is missing, zsync needs e.,g,. http:// or https://")
+		return errors.New("Scheme is missing in update information, zsync needs e.,g,. http:// or https://")
 	}
 	if strings.HasSuffix(u.Path, ".zsync") == false {
-		return errors.New(updateinformation + " does not end in .zsync")
+		return errors.New("Update information '" + updateinformation + "' does not end in .zsync")
 	}
 
 	return nil