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diff --git a/include/git2/sys/diff.h b/include/git2/sys/diff.h
new file mode 100644
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+++ b/include/git2/sys/diff.h
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+/*
+ * 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_sys_git_diff_h__
+#define INCLUDE_sys_git_diff_h__
+
+#include "git2/common.h"
+#include "git2/types.h"
+#include "git2/oid.h"
+#include "git2/diff.h"
+#include "git2/status.h"
+
+/**
+ * @file git2/sys/diff.h
+ * @brief Low-level Git diff utilities
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * Diff print callback that writes to a git_buf.
+ *
+ * This function is provided not for you to call it directly, but instead
+ * so you can use it as a function pointer to the `git_diff_print` or
+ * `git_patch_print` APIs.  When using those APIs, you specify a callback
+ * to actually handle the diff and/or patch data.
+ *
+ * Use this callback to easily write that data to a `git_buf` buffer.  You
+ * must pass a `git_buf *` value as the payload to the `git_diff_print`
+ * and/or `git_patch_print` function.  The data will be appended to the
+ * buffer (after any existing content).
+ */
+GIT_EXTERN(int) git_diff_print_callback__to_buf(
+	const git_diff_delta *delta,
+	const git_diff_hunk *hunk,
+	const git_diff_line *line,
+	void *payload); /**< payload must be a `git_buf *` */
+
+/**
+ * Diff print callback that writes to stdio FILE handle.
+ *
+ * This function is provided not for you to call it directly, but instead
+ * so you can use it as a function pointer to the `git_diff_print` or
+ * `git_patch_print` APIs.  When using those APIs, you specify a callback
+ * to actually handle the diff and/or patch data.
+ *
+ * Use this callback to easily write that data to a stdio FILE handle.  You
+ * must pass a `FILE *` value (such as `stdout` or `stderr` or the return
+ * value from `fopen()`) as the payload to the `git_diff_print`
+ * and/or `git_patch_print` function.  If you pass NULL, this will write
+ * data to `stdout`.
+ */
+GIT_EXTERN(int) git_diff_print_callback__to_file_handle(
+	const git_diff_delta *delta,
+	const git_diff_hunk *hunk,
+	const git_diff_line *line,
+	void *payload); /**< payload must be a `FILE *` */
+
+
+/**
+ * Performance data from diffing
+ */
+typedef struct {
+	unsigned int version;
+	size_t stat_calls; /**< Number of stat() calls performed */
+	size_t oid_calculations; /**< Number of ID calculations */
+} git_diff_perfdata;
+
+#define GIT_DIFF_PERFDATA_VERSION 1
+#define GIT_DIFF_PERFDATA_INIT {GIT_DIFF_PERFDATA_VERSION,0,0}
+
+/**
+ * Get performance data for a diff object.
+ *
+ * @param out Structure to be filled with diff performance data
+ * @param diff Diff to read performance data from
+ * @return 0 for success, <0 for error
+ */
+GIT_EXTERN(int) git_diff_get_perfdata(
+	git_diff_perfdata *out, const git_diff *diff);
+
+/**
+ * Get performance data for diffs from a git_status_list
+ */
+GIT_EXTERN(int) git_status_list_get_perfdata(
+	git_diff_perfdata *out, const git_status_list *status);
+
+/** @} */
+GIT_END_DECL
+#endif