Fixed a bug which can cause remote branch considered as local

Author: evianzhow

ObjectiveGit/GTBranch.m

@@ -193,7 +193,12 @@ - (GTBranch *)trackingBranchWithError:(NSError **)error success:(BOOL *)success
 }
 
 - (BOOL)updateTrackingBranch:(GTBranch *)trackingBranch error:(NSError **)error {
-	int result = git_branch_set_upstream(self.reference.git_reference, trackingBranch.shortName.UTF8String);
+  int result = GIT_ENOTFOUND;
+  if (trackingBranch.branchType == GTBranchTypeRemote) {
+    result = git_branch_set_upstream(self.reference.git_reference, [trackingBranch.name stringByReplacingOccurrencesOfString:[GTBranch remoteNamePrefix] withString:@""].UTF8String);
+	} else {
+		result = git_branch_set_upstream(self.reference.git_reference, trackingBranch.shortName.UTF8String);
+	}
 	if (result != GIT_OK) {
 		if (error != NULL) *error = [NSError git_errorFor:result description:@"Failed to update tracking branch for %@", self];
 		return NO;