Add stash apply & pop support

Author: tiennou

ObjectiveGit/GTRepository+Stashing.h

@@ -19,6 +19,14 @@ typedef NS_OPTIONS(NSInteger, GTRepositoryStashFlag) {
 	GTRepositoryStashFlagIncludeIgnored = GIT_STASH_INCLUDE_IGNORED
 };
 
+/// Flags for -applyStashAtIndex:flags:error: and
+/// -popStashAtIndex:flags:error.
+/// Those can be ORed together. See git_apply_flags for additional information.
+typedef NS_OPTIONS(NSInteger, GTRepositoryApplyFlag) {
+	GTRepositoryApplyFlagDefault = GIT_APPLY_DEFAULT,
+	GTRepositoryApplyFlagReinstateIndex = GIT_APPLY_REINSTATE_INDEX,
+};
+
 NS_ASSUME_NONNULL_BEGIN
 
 @interface GTRepository (Stashing)
@@ -41,6 +49,24 @@ NS_ASSUME_NONNULL_BEGIN
 ///         will cause enumeration to stop after the block returns. Must not be nil.
 - (void)enumerateStashesUsingBlock:(void (^)(NSUInteger index, NSString * __nullable message, GTOID * __nullable oid, BOOL *stop))block;
 
+/// Apply stashed changes.
+///
+/// index - The index of the stash to apply. 0 is the latest one.
+/// flags - The flags to use when applying the stash.
+/// error - If not NULL, set to any error that occurred.
+///
+/// Returns YES if the requested stash was successfully applied, NO otherwise.
+- (BOOL)applyStashAtIndex:(NSUInteger)index flags:(GTRepositoryApplyFlag)flags error:(NSError **)error;
+
+/// Pop stashed changes.
+///
+/// index - The index of the stash to apply. 0 is the most recent stash.
+/// flags - The flags to use when applying the stash.
+/// error - If not NULL, set to any error that occurred.
+///
+/// Returns YES if the requested stash was successfully applied, NO otherwise.
+- (BOOL)popStashAtIndex:(NSUInteger)index flags:(GTRepositoryApplyFlag)flags error:(NSError **)error;
+
 /// Drop a stash from the repository's list of stashes.
 ///
 /// index - The index of the stash to drop, where 0 is the most recent stash.

ObjectiveGit/GTRepository+Stashing.m

@@ -50,6 +50,24 @@ - (void)enumerateStashesUsingBlock:(GTRepositoryStashEnumerationBlock)block {
 	git_stash_foreach(self.git_repository, &stashEnumerationCallback, (__bridge void *)block);
 }
 
+- (BOOL)applyStashAtIndex:(NSUInteger)index flags:(GTRepositoryApplyFlag)flags error:(NSError **)error {
+	int gitError = git_stash_apply(self.git_repository, index, flags);
+	if (gitError != GIT_OK) {
+		if (error != NULL) *error = [NSError git_errorFor:gitError description:@"Failed to apply stash" failureReason:@"The stash at index %ld couldn't be applied.", index];
+		return NO;
+	}
+	return YES;
+}
+
+- (BOOL)popStashAtIndex:(NSUInteger)index flags:(GTRepositoryApplyFlag)flags error:(NSError **)error {
+	int gitError = git_stash_pop(self.git_repository, index, flags);
+	if (gitError != GIT_OK) {
+		if (error != NULL) *error = [NSError git_errorFor:gitError description:@"Failed to pop stash" failureReason:@"The stash at index %ld couldn't be applied.", index];
+		return NO;
+	}
+	return YES;
+}
+
 - (BOOL)dropStashAtIndex:(NSUInteger)index error:(NSError **)error {
 	int gitError = git_stash_drop(self.git_repository, index);
 	if (gitError != GIT_OK) {