Fix the GitRatchet problem on bare checkouts. (#611)

* Fix the GitRatchet problem on bare checkouts.

* Update changelog.

Author: nedtwigg

plugin-gradle/CHANGES.md

@@ -8,6 +8,8 @@ We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (
   * This removes the dependency to the no-longer-maintained Linux/Windows/macOs variants of J2V8.
   * This enables spotless to use the latest `prettier` versions (instead of being stuck at prettier version <= `1.19.0`)
   * Bumped default versions, prettier `1.16.4` -> `2.0.5`, tslint `5.12.1` -> `6.1.2`
+### Fixed
+* Using `ratchetFrom 'origin/main'` on a bare checkout generated a cryptic error, now generates a clear error. ([#608](https://github.com/diffplug/spotless/issues/608))
 
 ## [4.3.0] - 2020-06-05
 ### Deprecated

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

@@ -152,13 +152,16 @@ private Repository repositoryFor(Project project) throws IOException {
 	}
 
 	private static @Nullable Repository traverseParentsUntil(File startWith, File file) throws IOException {
-		do {
+		while (startWith != null) {
 			if (isGitRoot(startWith)) {
 				return createRepo(startWith);
 			} else {
 				startWith = startWith.getParentFile();
+				if (Objects.equals(startWith, file)) {
+					return null;
+				}
 			}
-		} while (!Objects.equals(startWith, file));
+		}
 		return null;
 	}