JGit CLI should check if calling itself when invoking native git exe

Bug: 480782
Change-Id: I0d7f7a648671e7ff678f2b19fe39b85f8835c061
Signed-off-by: Kaloyan Raev <kaloyan.r@zend.com>

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

@@ -556,6 +556,14 @@ public abstract class FS {
 			return null;
 		}
 
+		// Bug 480782: Check if the discovered git executable is JGit CLI
+		String v = readPipe(gitExe.getParentFile(),
+				new String[] { "git", "--version" }, //$NON-NLS-1$ //$NON-NLS-2$
+				Charset.defaultCharset().name());
+		if (v.startsWith("jgit")) { //$NON-NLS-1$
+			return null;
+		}
+
 		// Trick Git into printing the path to the config file by using "echo"
 		// as the editor.
 		Map<String, String> env = new HashMap<>();