libgit2 · pietbrauer · Feb 17, 2016 · Jan 30, 2016 · Jan 30, 2016 · Feb 2, 2016
diff --git a/ObjectiveGit/GTCommit.h b/ObjectiveGit/GTCommit.h
@@ -33,6 +33,7 @@
 @class GTSignature;
 @class GTTree;
 @class GTOID;
+@class GTIndex;
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -54,6 +55,17 @@ NS_ASSUME_NONNULL_BEGIN
 /// The underlying `git_object` as a `git_commit` object.
 - (git_commit *)git_commit __attribute__((objc_returns_inner_pointer));
 
+/// Merges the given commit into the receiver in memory and produces the result as
+/// an index.
+///
+/// otherCommit  - The commit with which the receiver should be merged with. Cannot be
+///                nil.
+/// error        - The error if one occurred.
+///
+/// Returns an index which represents the result of the merge, or nil if an error
+/// occurred.
+- (nullable GTIndex *)merge:(GTCommit *)otherCommit error:(NSError **)error;
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/ObjectiveGit/GTCommit.m b/ObjectiveGit/GTCommit.m
@@ -35,9 +35,11 @@
 #import "NSString+Git.h"
 #import "NSDate+GTTimeAdditions.h"
 #import "GTOID.h"
+#import "GTIndex.h"
 
 #import "git2/commit.h"
 #import "git2/errors.h"
+#import "git2/merge.h"
 
 @implementation GTCommit
 
@@ -130,4 +132,20 @@ - (NSArray *)parents {
 	return parents;
 }
 
+#pragma mark Merging
+
+- (GTIndex *)merge:(GTCommit *)otherCommit error:(NSError **)error {
+	NSParameterAssert(otherCommit != nil);
+
+	git_index *index;
+
+	int result = git_merge_commits(&index, self.repository.git_repository, self.git_commit, otherCommit.git_commit, NULL);
+	if (result != GIT_OK || index == NULL) {
+		if (error != NULL) *error = [NSError git_errorFor:result description:@"Failed to merge commit %@ with commit %@", self.SHA, otherCommit.SHA];
+		return nil;
+	}
+
+	return [[GTIndex alloc] initWithGitIndex:index repository:self.repository];
+}
+
 @end
diff --git a/ObjectiveGit/GTDiff.h b/ObjectiveGit/GTDiff.h
@@ -218,6 +218,23 @@ typedef NS_OPTIONS(NSInteger, GTDiffFindOptionsFlags) {
 /// Returns a newly created `GTDiff` object or nil on error.
 + (nullable instancetype)diffOldTree:(nullable GTTree *)oldTree withNewIndex:(nullable GTIndex *)newIndex inRepository:(GTRepository *)repository options:(nullable NSDictionary *)options error:(NSError **)error;
 
+/// Create a diff between two `GTIndex`es.
+///
+/// Both instances must be from the same repository, or an exception will be thrown.
+///
+/// oldIndex   - The "left" side of the diff. May be nil to represent an empty
+///              index.
+/// newIndex   - The "right" side of the diff. May be nil to represent an empty
+///              index.
+/// repository - The repository to be used for the diff. Cannot be nil.
+/// options    - A dictionary containing any of the above options key constants, or
+///              nil to use the defaults.
+/// error      - Populated with an `NSError` object on error, if information is
+///              available.
+///
+/// Returns a newly created `GTDiff` object or nil on error.
++ (nullable instancetype)diffOldIndex:(nullable GTIndex *)oldIndex withNewIndex:(nullable GTIndex *)newIndex inRepository:(GTRepository *)repository options:(nullable NSDictionary *)options error:(NSError **)error;
+
 /// Create a diff between a repository's current index.
 ///
 /// This is equivalent to `git diff --cached <treeish>` or if you pass the HEAD

diff --git a/ObjectiveGit/GTDiff.m b/ObjectiveGit/GTDiff.m
@@ -110,6 +110,22 @@ + (instancetype)diffOldTree:(GTTree *)oldTree withNewIndex:(GTIndex *)newIndex i
 	return [[self alloc] initWithGitDiff:diff repository:repository];
 }
 
++ (nullable instancetype)diffOldIndex:(GTIndex *)oldIndex withNewIndex:(GTIndex *)newIndex inRepository:(GTRepository *)repository options:(NSDictionary *)options error:(NSError **)error
+{
+	NSParameterAssert(repository != nil);
+
+	__block git_diff *diff;
+	int status = [self handleParsedOptionsDictionary:options usingBlock:^(git_diff_options *optionsStruct) {
+		return git_diff_index_to_index(&diff, repository.git_repository, oldIndex.git_index, newIndex.git_index, optionsStruct);
+	}];
+	if (status != GIT_OK) {
+		if (error != NULL) *error = [NSError git_errorFor:status description:@"Failed to create diff between %@ and %@", oldIndex, newIndex];
+		return nil;
+	}
+
+	return [[self alloc] initWithGitDiff:diff repository:repository];
+}
+
 + (instancetype)diffIndexFromTree:(GTTree *)tree inRepository:(GTRepository *)repository options:(NSDictionary *)options error:(NSError **)error {
 	NSParameterAssert(repository != nil);
 	NSParameterAssert(tree == nil || [tree.repository isEqual:repository]);