diff --git a/.travis.yml b/.travis.yml
index d0658a5ca..5ac7b1299 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,9 @@
 osx_image: xcode7
 language: objective-c
-install: script/bootstrap
+before_install: brew update
+install:
+  - brew uninstall xctool && brew install --HEAD xctool
+  - script/bootstrap
 script: script/cibuild
 notifications:
   email: false
diff --git a/Carthage/Checkouts/Quick b/Carthage/Checkouts/Quick
index b47b9ebf9..a22e9736e 160000
--- a/Carthage/Checkouts/Quick
+++ b/Carthage/Checkouts/Quick
@@ -1 +1 @@
-Subproject commit b47b9ebf97bc8e377070bd1e868c9f89b870c4fc
+Subproject commit a22e9736edf55168716dc2bb2f3256ce30061b0e
diff --git a/ObjectiveGit/GTBlame.h b/ObjectiveGit/GTBlame.h
index e5bd396de..22668133d 100644
--- a/ObjectiveGit/GTBlame.h
+++ b/ObjectiveGit/GTBlame.h
@@ -27,7 +27,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (nullable instancetype)initWithGitBlame:(git_blame *)blame NS_DESIGNATED_INITIALIZER;
 
 /// Get all the hunks in the blame. A convenience wrapper around `enumerateHunksUsingBlock:`
-@property (nonatomic, strong, readonly) NSArray *hunks;
+@property (nonatomic, strong, readonly) NSArray<GTBlameHunk *> *hunks;
 
 /// The number of hunks in the blame.
 @property (nonatomic, readonly) NSUInteger hunkCount;
diff --git a/ObjectiveGit/GTBranch.h b/ObjectiveGit/GTBranch.h
index 7a5155a8c..4a8766357 100644
--- a/ObjectiveGit/GTBranch.h
+++ b/ObjectiveGit/GTBranch.h
@@ -92,7 +92,7 @@ NS_ASSUME_NONNULL_BEGIN
 /// error       - If not NULL, set to any error that occurs.
 ///
 /// Returns a (possibly empty) array of GTCommits, or nil if an error occurs.
-- (nullable NSArray *)uniqueCommitsRelativeToBranch:(GTBranch *)otherBranch error:(NSError **)error;
+- (nullable NSArray<GTCommit *> *)uniqueCommitsRelativeToBranch:(GTBranch *)otherBranch error:(NSError **)error;
 
 /// Deletes the local branch and nils out the reference.
 - (BOOL)deleteWithError:(NSError **)error;
diff --git a/ObjectiveGit/GTCommit.h b/ObjectiveGit/GTCommit.h
index 23cdfc2f1..d721bf9ee 100644
--- a/ObjectiveGit/GTCommit.h
+++ b/ObjectiveGit/GTCommit.h
@@ -40,7 +40,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (nonatomic, readonly, strong, nullable) GTSignature *author;
 @property (nonatomic, readonly, strong, nullable) GTSignature *committer;
-@property (nonatomic, readonly, copy) NSArray *parents;
+@property (nonatomic, readonly, copy) NSArray<GTCommit *> *parents;
 @property (nonatomic, readonly, nullable) NSString *message;
 @property (nonatomic, readonly) NSString *messageDetails;
 @property (nonatomic, readonly) NSString *messageSummary;
diff --git a/ObjectiveGit/GTConfiguration.h b/ObjectiveGit/GTConfiguration.h
index f9346fe63..1e67030c1 100644
--- a/ObjectiveGit/GTConfiguration.h
+++ b/ObjectiveGit/GTConfiguration.h
@@ -9,6 +9,7 @@
 #import <Foundation/Foundation.h>
 #import "git2/types.h"
 
+@class GTRemote;
 @class GTRepository;
 @class GTSignature;
 
@@ -17,11 +18,11 @@ NS_ASSUME_NONNULL_BEGIN
 @interface GTConfiguration : NSObject
 
 @property (nonatomic, readonly, strong, nullable) GTRepository *repository;
-@property (nonatomic, readonly, copy) NSArray *configurationKeys;
+@property (nonatomic, readonly, copy) NSArray<NSString *> *configurationKeys;
 
 /// The GTRemotes in the config. If the configuration isn't associated with any
 /// repository, this will always be nil.
-@property (nonatomic, readonly, copy, nullable) NSArray *remotes;
+@property (nonatomic, readonly, copy, nullable) NSArray<GTRemote *> *remotes;
 
 - (instancetype)init NS_UNAVAILABLE;
 
diff --git a/ObjectiveGit/GTEnumerator.h b/ObjectiveGit/GTEnumerator.h
index aee9b3af2..d3d9d60c2 100644
--- a/ObjectiveGit/GTEnumerator.h
+++ b/ObjectiveGit/GTEnumerator.h
@@ -115,7 +115,7 @@ NS_ASSUME_NONNULL_BEGIN
 /// error - If not NULL, set to any error that occurs during traversal.
 ///
 /// Returns a (possibly empty) array of GTCommits, or nil if an error occurs.
-- (nullable NSArray *)allObjectsWithError:(NSError **)error;
+- (nullable NSArray<GTCommit *> *)allObjectsWithError:(NSError **)error;
 
 /// Gets the next commit.
 ///
diff --git a/ObjectiveGit/GTIndex.h b/ObjectiveGit/GTIndex.h
index 2c226f87a..35bdaefae 100644
--- a/ObjectiveGit/GTIndex.h
+++ b/ObjectiveGit/GTIndex.h
@@ -49,7 +49,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, readonly) NSUInteger entryCount;
 
 /// The GTIndexEntries in the index.
-@property (nonatomic, readonly, copy) NSArray *entries;
+@property (nonatomic, readonly, copy) NSArray<GTIndexEntry *> *entries;
 
 /// Whether the index contains conflicted files.
 @property (nonatomic, readonly) BOOL hasConflicts;
@@ -220,7 +220,7 @@ NS_ASSUME_NONNULL_BEGIN
 /// error     - When something goes wrong, this parameter is set. Optional.
 ///
 /// Returns `YES` in the event that everything has gone smoothly. Otherwise, `NO`.
-- (BOOL)updatePathspecs:(nullable NSArray *)pathspecs error:(NSError **)error passingTest:(nullable BOOL (^)(NSString *matchedPathspec, NSString *path, BOOL *stop))block;
+- (BOOL)updatePathspecs:(nullable NSArray<NSString*> *)pathspecs error:(NSError **)error passingTest:(nullable BOOL (^)(NSString *matchedPathspec, NSString *path, BOOL *stop))block;
 
 #pragma mark Deprecations
 - (nullable GTIndexEntry *)entryWithName:(NSString *)name __deprecated_msg("use entryWithPath: instead.");
diff --git a/ObjectiveGit/GTRemote.h b/ObjectiveGit/GTRemote.h
index a80ed3eb2..7b6b9f828 100644
--- a/ObjectiveGit/GTRemote.h
+++ b/ObjectiveGit/GTRemote.h
@@ -56,13 +56,13 @@ typedef enum {
 ///
 /// This array will contain NSStrings of the form
 /// `+refs/heads/*:refs/remotes/REMOTE/*`.
-@property (nonatomic, readonly, copy, nullable) NSArray *fetchRefspecs;
+@property (nonatomic, readonly, copy, nullable) NSArray<NSString *> *fetchRefspecs;
 
 /// The push refspecs for this remote.
 ///
 /// This array will contain NSStrings of the form
 /// `+refs/heads/*:refs/remotes/REMOTE/*`.
-@property (nonatomic, readonly, copy, nullable) NSArray *pushRefspecs;
+@property (nonatomic, readonly, copy, nullable) NSArray<NSString *> *pushRefspecs;
 
 /// Tests if a name is valid
 + (BOOL)isValidRemoteName:(NSString *)name;
diff --git a/ObjectiveGit/GTRepository+Committing.h b/ObjectiveGit/GTRepository+Committing.h
index fd4d1d23b..e77ee2115 100644
--- a/ObjectiveGit/GTRepository+Committing.h
+++ b/ObjectiveGit/GTRepository+Committing.h
@@ -25,11 +25,11 @@ NS_ASSUME_NONNULL_BEGIN
 /// error     - The error if one occurred.
 ///
 /// Returns the newly created commit, or nil if an error occurred.
-- (nullable GTCommit *)createCommitWithTree:(GTTree *)tree message:(NSString *)message author:(GTSignature *)author committer:(GTSignature *)committer parents:(nullable NSArray *)parents updatingReferenceNamed:(nullable NSString *)refName error:(NSError **)error;
+- (nullable GTCommit *)createCommitWithTree:(GTTree *)tree message:(NSString *)message author:(GTSignature *)author committer:(GTSignature *)committer parents:(nullable NSArray<GTCommit *> *)parents updatingReferenceNamed:(nullable NSString *)refName error:(NSError **)error;
 
 /// Creates a new commit using +createCommitWithTree:message:author:committer:parents:updatingReferenceNamed:error:
 /// with -userSignatureForNow as both the author and committer.
-- (nullable GTCommit *)createCommitWithTree:(GTTree *)tree message:(NSString *)message parents:(nullable NSArray *)parents updatingReferenceNamed:(nullable NSString *)refName error:(NSError **)error;
+- (nullable GTCommit *)createCommitWithTree:(GTTree *)tree message:(NSString *)message parents:(nullable NSArray<GTCommit *> *)parents updatingReferenceNamed:(nullable NSString *)refName error:(NSError **)error;
 
 @end
 
diff --git a/ObjectiveGit/GTRepository+RemoteOperations.h b/ObjectiveGit/GTRepository+RemoteOperations.h
index 33f22b13c..5afe6d2d1 100644
--- a/ObjectiveGit/GTRepository+RemoteOperations.h
+++ b/ObjectiveGit/GTRepository+RemoteOperations.h
@@ -48,7 +48,7 @@ extern NSString *const GTRepositoryRemoteOptionsCredentialProvider;
 /// error - The error if one ocurred. Can be NULL.
 ///
 /// Retruns a (possibly empty) array with GTFetchHeadEntry objects. Will not be nil.
-- (NSArray *)fetchHeadEntriesWithError:(NSError **)error;
+- (NSArray<GTFetchHeadEntry *> *)fetchHeadEntriesWithError:(NSError **)error;
 
 #pragma mark - Push
 
@@ -78,7 +78,7 @@ extern NSString *const GTRepositoryRemoteOptionsCredentialProvider;
 ///
 /// Returns YES if the push was successful, NO otherwise (and `error`, if provided,
 /// will point to an error describing what happened).
-- (BOOL)pushBranches:(NSArray *)branches toRemote:(GTRemote *)remote withOptions:(nullable NSDictionary *)options error:(NSError **)error progress:(nullable void (^)(unsigned int current, unsigned int total, size_t bytes, BOOL *stop))progressBlock;
+- (BOOL)pushBranches:(NSArray<GTBranch *> *)branches toRemote:(GTRemote *)remote withOptions:(nullable NSDictionary *)options error:(NSError **)error progress:(nullable void (^)(unsigned int current, unsigned int total, size_t bytes, BOOL *stop))progressBlock;
 
 /// Delete a remote branch
 ///
diff --git a/ObjectiveGit/GTRepository+Reset.h b/ObjectiveGit/GTRepository+Reset.h
index fc47b39ca..cbb06158a 100644
--- a/ObjectiveGit/GTRepository+Reset.h
+++ b/ObjectiveGit/GTRepository+Reset.h
@@ -37,7 +37,7 @@ NS_ASSUME_NONNULL_BEGIN
 /// error     - The error if one occurred.
 ///
 /// Returns whether the reset was successful.
-- (BOOL)resetPathspecs:(NSArray *)pathspecs toCommit:(GTCommit *)commit error:(NSError **)error;
+- (BOOL)resetPathspecs:(NSArray<NSString *> *)pathspecs toCommit:(GTCommit *)commit error:(NSError **)error;
 
 @end
 
diff --git a/ObjectiveGit/GTRepository.h b/ObjectiveGit/GTRepository.h
index ceb8337d9..48733ed2e 100644
--- a/ObjectiveGit/GTRepository.h
+++ b/ObjectiveGit/GTRepository.h
@@ -260,7 +260,7 @@ extern NSString * const GTRepositoryInitOptionsOriginURLString;
 ///
 /// returns an array of NSStrings holding the names of the references
 /// returns nil if an error occurred and fills the error parameter
-- (nullable NSArray *)referenceNamesWithError:(NSError **)error;
+- (nullable NSArray<NSString *> *)referenceNamesWithError:(NSError **)error;
 
 /// Get the HEAD reference.
 ///
@@ -274,14 +274,14 @@ extern NSString * const GTRepositoryInitOptionsOriginURLString;
 /// error - If not NULL, set to any error that occurs.
 ///
 /// Returns an array of GTBranches or nil if an error occurs.
-- (nullable NSArray *)localBranchesWithError:(NSError **)error;
+- (nullable NSArray<GTBranch *> *)localBranchesWithError:(NSError **)error;
 
 /// Get the remote branches.
 ///
 /// error - If not NULL, set to any error that occurs.
 ///
 /// Returns an array of GTBranches or nil if an error occurs.
-- (nullable NSArray *)remoteBranchesWithError:(NSError **)error;
+- (nullable NSArray<GTBranch *> *)remoteBranchesWithError:(NSError **)error;
 
 /// Get branches with names sharing a given prefix.
 ///
@@ -289,7 +289,7 @@ extern NSString * const GTRepositoryInitOptionsOriginURLString;
 /// error - If not NULL, set to any error that occurs.
 ///
 /// Returns an array of GTBranches or nil if an error occurs.
-- (nullable NSArray *)branchesWithPrefix:(NSString *)prefix error:(NSError **)error;
+- (nullable NSArray<GTBranch *> *)branchesWithPrefix:(NSString *)prefix error:(NSError **)error;
 
 /// Get the local and remote branches and merge them together by combining local
 /// branches with their remote branch, if they have one.
@@ -297,21 +297,21 @@ extern NSString * const GTRepositoryInitOptionsOriginURLString;
 /// error - If not NULL, set to any error that occurs.
 ///
 /// Returns an array of GTBranches or nil if an error occurs.
-- (nullable NSArray *)branches:(NSError **)error;
+- (nullable NSArray<GTBranch *> *)branches:(NSError **)error;
 
 /// List all remotes in the repository
 ///
 /// error - will be filled if an error occurs
 ///
 /// returns an array of NSStrings holding the names of the remotes, or nil if an error occurred
-- (nullable NSArray *)remoteNamesWithError:(NSError **)error;
+- (nullable NSArray<NSString *> *)remoteNamesWithError:(NSError **)error;
 
 /// Get all tags in the repository.
 ///
 /// error - If not NULL, set to any error that occurs.
 ///
 /// Returns an array of GTTag or nil if an error occurs.
-- (nullable NSArray *)allTagsWithError:(NSError **)error;
+- (nullable NSArray<GTTag *> *)allTagsWithError:(NSError **)error;
 
 /// Count all commits in the current branch (HEAD)
 ///
@@ -367,7 +367,7 @@ extern NSString * const GTRepositoryInitOptionsOriginURLString;
 /// error(out)   - will be filled if an error occurs
 ///
 /// returns the local commits, an empty array if there is no remote branch, or nil if an error occurred
-- (nullable NSArray *)localCommitsRelativeToRemoteBranch:(GTBranch *)remoteBranch error:(NSError **)error;
+- (nullable NSArray<GTCommit *> *)localCommitsRelativeToRemoteBranch:(GTBranch *)remoteBranch error:(NSError **)error;
 
 /// Retrieves git's "prepared message" for the next commit, like the default
 /// message pre-filled when committing after a conflicting merge.
diff --git a/ObjectiveGit/GTRepository.m b/ObjectiveGit/GTRepository.m
index 49e59ce07..332c565f4 100644
--- a/ObjectiveGit/GTRepository.m
+++ b/ObjectiveGit/GTRepository.m
@@ -111,21 +111,6 @@ - (void)dealloc {
 
 #pragma mark API
 
-+ (BOOL)isAGitDirectory:(NSURL *)directory {
-	NSFileManager *fm = [[NSFileManager alloc] init];
-	BOOL isDir = NO;
-	NSURL *headFileURL = [directory URLByAppendingPathComponent:@"HEAD"];
-
-	if ([fm fileExistsAtPath:headFileURL.path isDirectory:&isDir] && !isDir) {
-		NSURL *objectsDir = [directory URLByAppendingPathComponent:@"objects"];
-		if ([fm fileExistsAtPath:objectsDir.path isDirectory:&isDir] && isDir) {
-			return YES;
-		}
-	}
-
-	return NO;
-}
-
 + (instancetype)initializeEmptyRepositoryAtFileURL:(NSURL *)localFileURL options:(NSDictionary *)optionsDict error:(NSError **)error {
 	if (!localFileURL.isFileURL || localFileURL.path == nil) {
 		if (error != NULL) *error = [NSError errorWithDomain:NSCocoaErrorDomain code:NSFileWriteUnsupportedSchemeError userInfo:@{ NSLocalizedDescriptionKey: NSLocalizedString(@"Invalid file path URL to initialize repository.", @"") }];
diff --git a/ObjectiveGit/GTTree.h b/ObjectiveGit/GTTree.h
index 32e4b1d2f..3635e561a 100644
--- a/ObjectiveGit/GTTree.h
+++ b/ObjectiveGit/GTTree.h
@@ -47,7 +47,7 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, readonly) NSUInteger entryCount;
 
 /// The contents of the tree, as an array of whose objects are of type `GTTreeEntry`
-@property (nonatomic, strong, readonly, nullable) NSArray *entries;
+@property (nonatomic, strong, readonly, nullable) NSArray<GTTreeEntry *> *entries;
 
 /// The underlying `git_object` as a `git_tree` object.
 - (git_tree *)git_tree __attribute__((objc_returns_inner_pointer));
diff --git a/README.md b/README.md
index 863c7f9a5..d3cfdc793 100644
--- a/README.md
+++ b/README.md
@@ -88,6 +88,8 @@ There are three ways of including ObjectiveGit in a project:
 
 1. Commit the [`Cartfile.resolved`](https://github.com/Carthage/Carthage/blob/master/Documentation/Artifacts.md#cartfileresolved)
 
+2. Under “Build Settings”, add the following to “Header Search Paths”: `$(SRCROOT)/Carthage/Build/iOS/ObjectiveGit.framework/Headers/` to avoid [`git2/filter.h file not found` errors](https://github.com/libgit2/objective-git/issues/441).
+
 The different instructions for iOS works around an [App Store submission bug](http://www.openradar.me/radar?id=6409498411401216) triggered by universal binaries.
 
 
diff --git a/script/cibuild b/script/cibuild
index 6224abcbf..41e703068 100755
--- a/script/cibuild
+++ b/script/cibuild
@@ -90,10 +90,16 @@ run_xctool ()
 {
     if [ -n "$XCWORKSPACE" ]
     then
-        xctool -workspace "$XCWORKSPACE" $XCTOOL_OPTIONS "$@" 2>&1
+        xctool -workspace "$XCWORKSPACE" $XCTOOL_OPTIONS "$@" \
+            ONLY_ACTIVE_ARCH=NO \
+            CODE_SIGN_IDENTITY="" \
+            CODE_SIGNING_REQUIRED=NO 2>&1
     elif [ -n "$XCODEPROJ" ]
     then
-        xctool -project "$XCODEPROJ" $XCTOOL_OPTIONS "$@" 2>&1
+        xctool -project "$XCODEPROJ" $XCTOOL_OPTIONS "$@" \
+            ONLY_ACTIVE_ARCH=NO \
+            CODE_SIGN_IDENTITY="" \
+            CODE_SIGNING_REQUIRED=NO 2>&1
     else
         echo "*** No workspace or project file found."
         exit 1