Set the rootDir as / instead of // if the project is in the root of the filesystem (#732)

Author: nedtwigg

Diff for: CHANGES.md

@@ -10,6 +10,8 @@ This document is intended for Spotless developers.
 We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (starting after version `1.27.0`).
 
 ## [Unreleased]
+### Fixed
+* Fixed a bug which occurred if the root directory of the project was also the filesystem root ([#732](https://github.com/diffplug/spotless/pull/732))
 
 ## [2.10.1] - 2020-11-13
 ### Fixed

Diff for: lib-extra/src/main/java/com/diffplug/spotless/extra/GitAttributesLineEndings.java

@@ -108,7 +108,8 @@ static class CachedEndings implements Serializable {
 		final ConcurrentRadixTree<String> hasNonDefaultEnding = new ConcurrentRadixTree<>(new DefaultCharSequenceNodeFactory());
 
 		CachedEndings(File projectDir, Runtime runtime, Iterable<File> toFormat) {
-			rootDir = FileSignature.pathNativeToUnix(projectDir.getAbsolutePath()) + "/";
+			String rootPath = FileSignature.pathNativeToUnix(projectDir.getAbsolutePath());
+			rootDir = rootPath.equals("/") ? rootPath : rootPath + "/";
 			defaultEnding = runtime.defaultEnding;
 			for (File file : toFormat) {
 				String ending = runtime.getEndingFor(file);

Diff for: plugin-gradle/CHANGES.md

@@ -3,6 +3,8 @@
 We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (starting after version `3.27.0`).
 
 ## [Unreleased]
+### Fixed
+* Fixed a bug which occurred if the root directory of the project was also the filesystem root ([#732](https://github.com/diffplug/spotless/pull/732))
 
 ## [5.8.1] - 2020-11-13
 ### Fixed

Diff for: plugin-maven/CHANGES.md

@@ -3,6 +3,8 @@
 We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (starting after version `1.27.0`).
 
 ## [Unreleased]
+### Fixed
+* Fixed a bug which occurred if the root directory of the project was also the filesystem root ([#732](https://github.com/diffplug/spotless/pull/732))
 
 ## [2.6.0] - 2020-11-13
 ### Added