apply: introduce `git_apply_tree`

Introduce `git_apply_tree`, which will apply a `git_diff` to a given
`git_tree`, allowing an in-memory patch application for a repository.

2 files changed, 42 insertions, 0 deletions

diff --git a/include/git2.h b/include/git2.h
index e182ce924..9239b48c8 100644
--- a/include/git2.h
+++ b/include/git2.h
@@ -9,6 +9,7 @@
 #define INCLUDE_git_git_h__
 
 #include "git2/annotated_commit.h"
+#include "git2/apply.h"
 #include "git2/attr.h"
 #include "git2/blob.h"
 #include "git2/blame.h"
diff --git a/include/git2/apply.h b/include/git2/apply.h
new file mode 100644
index 000000000..a4ec4fc08
--- /dev/null
+++ b/include/git2/apply.h
@@ -0,0 +1,41 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_git_apply_h__
+#define INCLUDE_git_apply_h__
+
+#include "common.h"
+#include "types.h"
+#include "oid.h"
+#include "diff.h"
+
+/**
+ * @file git2/apply.h
+ * @brief Git patch application routines
+ * @defgroup git_apply Git patch application routines
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * Apply a `git_diff` to a `git_tree`, and return the resulting image
+ * as an index.
+ *
+ * @param out the postimage of the application
+ * @param repo the repository to apply
+ * @param preimage the tree to apply the diff to
+ * @param diff the diff to apply
+ */
+GIT_EXTERN(int) git_apply_to_tree(
+	git_index **out,
+	git_repository *repo,
+	git_tree *preimage,
+	git_diff *diff);
+
+/** @} */
+GIT_END_DECL
+#endif