Better error message, and loop that into the README.

Author: nedtwigg

plugin-gradle/README.md

@@ -146,26 +146,22 @@ Starting in version `7.0.0`, Spotless now supports linting in addition to format
 
 ```console
 user@machine repo % ./gradlew build
-:spotlessJavaCheck FAILED
-  The following files had format violations:
-  src\main\java\com\diffplug\gradle\spotless\FormatExtension.java
-    -\t\t····if·(targets.length·==·0)·{
-    +\t\tif·(targets.length·==·0)·{
+:spotlessKotlinCheck FAILED
+  There were 2 lint error(s), they must be fixed or suppressed.
+    src/main/kotlin/com/diffplug/Foo.kt:L7 ktlint(standard:no-wildcard-imports) Wildcard import
+    src/main/kotlin/com/diffplug/Bar.kt:L9 ktlint(standard:no-wildcard-imports) Wildcard import 
   Resolve these lints or suppress with `suppressLintsFor`
 ```
 
 To suppress lints, you can do this:
 
 ```gradle
 spotless {
-  suppressLintsFor { // applies to all formats
-    file = 'src/blah/blah'
-  }
   kotlin {
-    ktfmt()
-    suppressLintsFor { // applies to only the kotlin formats
+    ktlint()
+    suppressLintsFor {
       step = 'ktlint'
-      shortCode = 'rename'
+      shortCode = 'standard:no-wildcard-imports'
     }
   }
 }

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessTaskService.java

@@ -199,7 +199,7 @@ public void visitFile(FileVisitDetails fileVisitDetails) {
 					}
 				}
 			}
-			builder.setLength(builder.length() - 1); // remove trailing newline
+			builder.append("Resolve these lints or suppress with `suppressLintsFor`");
 			return builder.toString();
 		}
 	}

plugin-gradle/src/test/java/com/diffplug/gradle/spotless/ErrorShouldRethrowTest.java

@@ -70,7 +70,8 @@ void anyExceptionShouldFail() throws Exception {
 				"* What went wrong:",
 				"Execution failed for task ':spotlessMiscCheck'.",
 				"> There were 1 lint error(s), they must be fixed or suppressed.",
-				"  README.md:LINE_UNDEFINED noSwearingStep(swearing) No swearing!");
+				"  README.md:LINE_UNDEFINED noSwearingStep(swearing) No swearing!",
+				"  Resolve these lints or suppress with `suppressLintsFor`");
 	}
 
 	@Test
@@ -119,7 +120,8 @@ void failsIfNeitherStepNorFileExempted() throws Exception {
 				"* What went wrong:",
 				"Execution failed for task ':spotlessMiscCheck'.",
 				"> There were 1 lint error(s), they must be fixed or suppressed.",
-				"  README.md:LINE_UNDEFINED noSwearingStep(swearing) No swearing!");
+				"  README.md:LINE_UNDEFINED noSwearingStep(swearing) No swearing!",
+				"  Resolve these lints or suppress with `suppressLintsFor`");
 	}
 
 	private void expectSuccess() throws Exception {