Fix possible SIOOBE in RefDirectory.parsePackedRefs

This SIOOBE happens reproducibly when trying to access
a repository containing Cygwin symlinks

Change-Id: I25f103fcc723bac7bfaaeee333a86f11627a92c7
Signed-off-by: Marc Strapetz <marc.strapetz@syntevo.com>
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -465,6 +465,7 @@ packDoesNotMatchIndex=Pack {0} does not match index
 packedRefsHandleIsStale=packed-refs handle is stale, {0}. retry
 packetSizeMustBeAtLeast=packet size {0} must be >= {1}
 packetSizeMustBeAtMost=packet size {0} must be <= {1}
+packedRefsCorruptionDetected=packed-refs corruption detected: {0}
 packfileCorruptionDetected=Packfile corruption detected: {0}
 packFileInvalid=Pack file invalid: {0}
 packfileIsTruncated=Packfile {0} is truncated.

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -524,6 +524,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String packedRefsHandleIsStale;
 	/***/ public String packetSizeMustBeAtLeast;
 	/***/ public String packetSizeMustBeAtMost;
+	/***/ public String packedRefsCorruptionDetected;
 	/***/ public String packfileCorruptionDetected;
 	/***/ public String packFileInvalid;
 	/***/ public String packfileIsTruncated;

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java

@@ -843,6 +843,11 @@ public class RefDirectory extends RefDatabase {
 			}
 
 			int sp = p.indexOf(' ');
+			if (sp < 0) {
+				throw new IOException(MessageFormat.format(
+						JGitText.get().packedRefsCorruptionDetected,
+						packedRefsFile.getAbsolutePath()));
+			}
 			ObjectId id = ObjectId.fromString(p.substring(0, sp));
 			String name = copy(p, sp + 1, p.length());
 			ObjectIdRef cur;