Allow detection of case insensitive file systems

Change-Id: I03f59d07bcc3338ef8d392cbd940799186ca03bd
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/AddCommandTest.java

 			public boolean canExecute(File f) {
 				return true;
 			}
+
+			@Override
+			public boolean isCaseSensitive() {
+				return false;
+			}
 		};
 
 		Git git = Git.open(db.getDirectory(), executableFs);
 			public boolean canExecute(File f) {
 				return false;
 			}
+
+			@Override
+			public boolean isCaseSensitive() {
+				return false;
+			}
 		};
 
 		config = db.getConfig();

org.eclipse.jgit.test/tst/org/eclipse/jgit/api/CommitCommandTest.java

 			public boolean canExecute(File f) {
 				return true;
 			}
+
+			@Override
+			public boolean isCaseSensitive() {
+				return true;
+			}
 		};
 
 		Git git = Git.open(db.getDirectory(), executableFs);
 			public boolean canExecute(File f) {
 				return false;
 			}
+
+			@Override
+			public boolean isCaseSensitive() {
+				return true;
+			}
 		};
 
 		config = db.getConfig();

org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java

 	 */
 	public abstract boolean supportsExecute();
 
+	/**
+	 * Is this file system case sensitive
+	 *
+	 * @return true if this implementation is case sensitive
+	 */
+	public abstract boolean isCaseSensitive();
+
 	/**
 	 * Determine if the file is executable (or not).
 	 * <p>

org.eclipse.jgit/src/org/eclipse/jgit/util/FS_POSIX.java

 		super(src);
 	}
 
+	@Override
+	public boolean isCaseSensitive() {
+		if (isMacOS())
+			return false;
+		else
+			return true;
+	}
+
 	@Override
 	public ProcessBuilder runInShell(String cmd, String[] args) {
 		List<String> argv = new ArrayList<String>(4 + args.length);

org.eclipse.jgit/src/org/eclipse/jgit/util/FS_Win32.java

 import java.util.List;
 
 class FS_Win32 extends FS {
+
 	static boolean isWin32() {
 		final String osDotName = AccessController
 				.doPrivileged(new PrivilegedAction<String>() {
 		return false;
 	}
 
+	@Override
+	public boolean isCaseSensitive() {
+		return false;
+	}
+
 	@Override
 	public boolean retryFailedLockFileCommit() {
 		return true;