containertool: Allow destination repository to be set by an environment variable

Author: euanh

Sources/containertool/containertool.swift

@@ -32,7 +32,7 @@ enum AllowHTTP: String, ExpressibleByArgument, CaseIterable { case source, desti
     private var defaultRegistry: String?
 
     @Option(help: "Repository path")
-    private var repository: String
+    private var repository: String?
 
     @Argument(help: "Executable to package")
     private var executable: String
@@ -114,7 +114,14 @@ enum AllowHTTP: String, ExpressibleByArgument, CaseIterable { case source, desti
         // MARK: Apply defaults for unspecified configuration flags
 
         let env = ProcessInfo.processInfo.environment
+
         let defaultRegistry = defaultRegistry ?? env["CONTAINERTOOL_DEFAULT_REGISTRY"] ?? "docker.io"
+        guard let repository = repository ?? env["CONTAINERTOOL_REPOSITORY"] else {
+            throw ValidationError(
+                "Please specify the destination repository using --repository or CONTAINERTOOL_REPOSITORY"
+            )
+        }
+
         let username = defaultUsername ?? env["CONTAINERTOOL_DEFAULT_USERNAME"]
         let password = defaultPassword ?? env["CONTAINERTOOL_DEFAULT_PASSWORD"]
         let from = from ?? env["CONTAINERTOOL_BASE_IMAGE"] ?? "swift:slim"

scripts/test-plugin-output-streaming.sh

@@ -46,9 +46,8 @@ swift package --package-path "$PKGPATH" --allow-network-connections all build-co
 set -o pipefail
 
 # This checks that the output lines are not broken, but not that they appear in the correct order
-grep -F -x -e "error: Missing expected argument '--repository <repository>'" \
-           -e "error: Help:  --repository <repository>  Repository path" \
-           -e "error: Usage: containertool [<options>] --repository <repository> <executable>" \
+grep -F -x -e "error: Please specify the destination repository using --repository or CONTAINERTOOL_REPOSITORY" \
+           -e "error: Usage: containertool [<options>] <executable>" \
            -e "error:   See 'containertool --help' for more information." "$PKGPATH/output"
 
 log Plugin error output: PASSED