add remote branch deletion feature

Author: evianzhow

ObjectiveGit/GTRepository+RemoteOperations.h

@@ -75,4 +75,17 @@ extern NSString *const GTRepositoryRemoteOptionsCredentialProvider;
 /// will point to an error describing what happened).
 - (BOOL)pushBranches:(NSArray *)branches toRemote:(GTRemote *)remote withOptions:(NSDictionary *)options error:(NSError **)error progress:(void (^)(unsigned int current, unsigned int total, size_t bytes, BOOL *stop))progressBlock;
 
+/// Delete a remote branch
+///
+/// branch        - The branch to push. Must not be nil.
+/// remote        - The remote to push to. Must not be nil.
+/// options       - Options applied to the push operation. Can be NULL.
+///                 Recognized options are:
+///                 `GTRepositoryRemoteOptionsCredentialProvider`
+/// error         - The error if one occurred. Can be NULL.
+/// progressBlock - An optional callback for monitoring progress.
+///
+/// Returns YES if the push was successful, NO otherwise (and `error`, if provided,
+/// will point to an error describing what happened).
+- (BOOL)deleteBranch:(GTBranch *)branch fromRemote:(GTRemote *)remote withOptions:(NSDictionary *)options error:(NSError **)error progress:(void (^)(unsigned int current, unsigned int total, size_t bytes, BOOL *stop))progressBlock;
 @end

ObjectiveGit/GTRepository+RemoteOperations.m

@@ -196,6 +196,16 @@ - (BOOL)pushBranches:(NSArray *)branches toRemote:(GTRemote *)remote withOptions
 	return [self pushRefspecs:refspecs toRemote:remote withOptions:options error:error progress:progressBlock];
 }
 
+#pragma mark - Deletion (Public)
+- (BOOL)deleteBranch:(GTBranch *)branch fromRemote:(GTRemote *)remote withOptions:(NSDictionary *)options error:(NSError **)error progress:(GTRemotePushTransferProgressBlock)progressBlock {
+		NSParameterAssert(branch != nil);
+		NSParameterAssert(remote != nil);
+		
+		NSArray *refspecs = @[[NSString stringWithFormat:@":refs/heads/%@", branch.shortName]];
+		
+		return [self pushRefspecs:refspecs toRemote:remote withOptions:options error:error progress:progressBlock];
+}
+
 #pragma mark - Push (Private)
 
 - (BOOL)pushRefspecs:(NSArray *)refspecs toRemote:(GTRemote *)remote withOptions:(NSDictionary *)options error:(NSError **)error progress:(GTRemotePushTransferProgressBlock)progressBlock {