Polish "Explicit error message if source is not an archive"

See gh-31997

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/main/java/org/springframework/boot/jarmode/layertools/Context.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -56,7 +56,7 @@ class Context {
 	 */
 	Context(File archiveFile, File workingDir) {
 		Assert.state(isExistingFile(archiveFile), "Unable to find source archive");
-		Assert.state(isJarOrWar(archiveFile), "Source archive doesn't end with .jar or .war");
+		Assert.state(isJarOrWar(archiveFile), "Source archive " + archiveFile + " must end with .jar or .war");
 		this.archiveFile = archiveFile;
 		this.workingDir = workingDir;
 		this.relativeDir = deduceRelativeDir(archiveFile.getParentFile(), this.workingDir);

spring-boot-project/spring-boot-tools/spring-boot-jarmode-layertools/src/test/java/org/springframework/boot/jarmode/layertools/ContextTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -55,7 +55,7 @@ class ContextTests {
 		File zip = new File(this.temp, "test.zip");
 		Files.createFile(zip.toPath());
 		assertThatIllegalStateException().isThrownBy(() -> new Context(zip, this.temp))
-				.withMessage("Unable to find source archive");
+				.withMessageContaining("test.zip must end with .jar or .war");
 	}
 
 	@Test