thodg/libgit2

diff --git a/src/merge.c b/src/merge.c
index fc5088c..89b8e85 100644
--- a/src/merge.c
+++ b/src/merge.c
@@ -61,12 +61,6 @@ struct merge_diff_df_data {
 	git_merge_diff *prev_conflict;
 };
 
-GIT_INLINE(int) merge_diff_detect_binary(
-	bool *binary_out,
-	git_repository *repo,
-	const git_merge_diff *conflict);
-
-
 /* Merge base computation */
 
 int merge_bases_many(git_commit_list **out, git_revwalk **walk_out, git_repository *repo, size_t length, const git_oid input_array[])
@@ -668,7 +662,6 @@ static int merge_conflict_resolve_automerge(
 	git_odb *odb = NULL;
 	git_oid automerge_oid;
 	int error = 0;
-	bool binary = false;
 
 	assert(resolved && diff_list && conflict);
 
@@ -703,12 +696,6 @@ static int merge_conflict_resolve_automerge(
 		strcmp(conflict->ancestor_entry.path, conflict->their_entry.path) != 0)
 		return 0;
 
-	/* Reject binary conflicts */
-	if ((error = merge_diff_detect_binary(&binary, diff_list->repo, conflict)) < 0)
-		return error;
-	if (binary)
-		return 0;
-
 	ancestor = GIT_MERGE_INDEX_ENTRY_EXISTS(conflict->ancestor_entry) ?
 		&conflict->ancestor_entry : NULL;
 	ours = GIT_MERGE_INDEX_ENTRY_EXISTS(conflict->our_entry) ?
@@ -1314,48 +1301,6 @@ GIT_INLINE(int) merge_diff_detect_type(
 	return 0;
 }
 
-GIT_INLINE(int) merge_diff_detect_binary(
-	bool *binary_out,
-	git_repository *repo,
-	const git_merge_diff *conflict)
-{
-	git_blob *ancestor_blob = NULL, *our_blob = NULL, *their_blob = NULL;
-	int error = 0;
-	bool binary = false;
-
-	if (GIT_MERGE_INDEX_ENTRY_ISFILE(conflict->ancestor_entry)) {
-		if ((error = git_blob_lookup(&ancestor_blob, repo, &conflict->ancestor_entry.id)) < 0)
-			goto done;
-
-		binary = git_blob_is_binary(ancestor_blob);
-	}
-
-	if (!binary &&
-		GIT_MERGE_INDEX_ENTRY_ISFILE(conflict->our_entry)) {
-		if ((error = git_blob_lookup(&our_blob, repo, &conflict->our_entry.id)) < 0)
-			goto done;
-
-		binary = git_blob_is_binary(our_blob);
-	}
-
-	if (!binary &&
-		GIT_MERGE_INDEX_ENTRY_ISFILE(conflict->their_entry)) {
-		if ((error = git_blob_lookup(&their_blob, repo, &conflict->their_entry.id)) < 0)
-			goto done;
-
-		binary = git_blob_is_binary(their_blob);
-	}
-
-	*binary_out = binary;
-
-done:
-	git_blob_free(ancestor_blob);
-	git_blob_free(our_blob);
-	git_blob_free(their_blob);
-
-	return error;
-}
-
 GIT_INLINE(int) index_entry_dup_pool(
 	git_index_entry *out,
 	git_pool *pool,
diff --git a/src/merge_file.c b/src/merge_file.c
index 6d89b08..b174231 100644
--- a/src/merge_file.c
+++ b/src/merge_file.c
@@ -15,9 +15,15 @@
 #include "git2/repository.h"
 #include "git2/object.h"
 #include "git2/index.h"
+#include "git2/merge.h"
 
 #include "xdiff/xdiff.h"
 
+/* only examine the first 8000 bytes for binaryness.
+ * https://github.com/git/git/blob/77bd3ea9f54f1584147b594abc04c26ca516d987/xdiff-interface.c#L197
+ */
+#define GIT_MERGE_FILE_BINARY_SIZE 8000
+
 #define GIT_MERGE_FILE_SIDE_EXISTS(X)	((X)->mode != 0)
 
 GIT_INLINE(const char *) merge_file_best_path(
@@ -100,7 +106,7 @@ static void merge_file_normalize_opts(
 	}
 }
 
-static int git_merge_file__from_inputs(
+static int merge_file__xdiff(
 	git_merge_file_result *out,
 	const git_merge_file_input *ancestor,
 	const git_merge_file_input *ours,
@@ -189,6 +195,63 @@ done:
 	return error;
 }
 
+static bool merge_file__is_binary(const git_merge_file_input *file)
+{
+	size_t len = file ? file->size : 0;
+
+	if (len > GIT_MERGE_FILE_XDIFF_MAX)
+		return true;
+	if (len > GIT_MERGE_FILE_BINARY_SIZE)
+		len = GIT_MERGE_FILE_BINARY_SIZE;
+
+	return len ? (memchr(file->ptr, 0, len) != NULL) : false;
+}
+
+static int merge_file__binary(
+	git_merge_file_result *out,
+	const git_merge_file_input *ours,
+	const git_merge_file_input *theirs,
+	const git_merge_file_options *given_opts)
+{
+	const git_merge_file_input *favored = NULL;
+
+	memset(out, 0x0, sizeof(git_merge_file_result));
+
+	if (given_opts && given_opts->favor == GIT_MERGE_FILE_FAVOR_OURS)
+		favored = ours;
+	else if (given_opts && given_opts->favor == GIT_MERGE_FILE_FAVOR_THEIRS)
+		favored = theirs;
+	else
+		goto done;
+
+	if ((out->path = git__strdup(favored->path)) == NULL ||
+		(out->ptr = git__malloc(favored->size)) == NULL)
+		goto done;
+
+	memcpy((char *)out->ptr, favored->ptr, favored->size);
+	out->len = favored->size;
+	out->mode = favored->mode;
+	out->automergeable = 1;
+
+done:
+	return 0;
+}
+
+static int merge_file__from_inputs(
+	git_merge_file_result *out,
+	const git_merge_file_input *ancestor,
+	const git_merge_file_input *ours,
+	const git_merge_file_input *theirs,
+	const git_merge_file_options *given_opts)
+{
+	if (merge_file__is_binary(ancestor) ||
+		merge_file__is_binary(ours) ||
+		merge_file__is_binary(theirs))
+		return merge_file__binary(out, ours, theirs, given_opts);
+
+	return merge_file__xdiff(out, ancestor, ours, theirs, given_opts);
+}
+
 static git_merge_file_input *git_merge_file__normalize_inputs(
 	git_merge_file_input *out,
 	const git_merge_file_input *given)
@@ -223,7 +286,7 @@ int git_merge_file(
 	ours = git_merge_file__normalize_inputs(&inputs[1], ours);
 	theirs = git_merge_file__normalize_inputs(&inputs[2], theirs);
 
-	return git_merge_file__from_inputs(out, ancestor, ours, theirs, options);
+	return merge_file__from_inputs(out, ancestor, ours, theirs, options);
 }
 
 int git_merge_file_from_index(
@@ -234,8 +297,8 @@ int git_merge_file_from_index(
 	const git_index_entry *theirs,
 	const git_merge_file_options *options)
 {
-	git_merge_file_input inputs[3] = { {0} },
-		*ancestor_input = NULL, *our_input = NULL, *their_input = NULL;
+	git_merge_file_input *ancestor_ptr = NULL,
+		ancestor_input = {0}, our_input = {0}, their_input = {0};
 	git_odb *odb = NULL;
 	git_odb_object *odb_object[3] = { 0 };
 	int error = 0;
@@ -249,27 +312,20 @@ int git_merge_file_from_index(
 
 	if (ancestor) {
 		if ((error = git_merge_file__input_from_index(
-			&inputs[0], &odb_object[0], odb, ancestor)) < 0)
+			&ancestor_input, &odb_object[0], odb, ancestor)) < 0)
 			goto done;
 
-		ancestor_input = &inputs[0];
+		ancestor_ptr = &ancestor_input;
 	}
 
 	if ((error = git_merge_file__input_from_index(
-		&inputs[1], &odb_object[1], odb, ours)) < 0)
-		goto done;
-
-	our_input = &inputs[1];
-
-	if ((error = git_merge_file__input_from_index(
-		&inputs[2], &odb_object[2], odb, theirs)) < 0)
+			&our_input, &odb_object[1], odb, ours)) < 0 ||
+		(error = git_merge_file__input_from_index(
+			&their_input, &odb_object[2], odb, theirs)) < 0)
 		goto done;
 
-	their_input = &inputs[2];
-
-	if ((error = git_merge_file__from_inputs(out,
-		ancestor_input, our_input, their_input, options)) < 0)
-		goto done;
+	error = merge_file__from_inputs(out,
+		ancestor_ptr, &our_input, &their_input, options);
 
 done:
 	git_odb_object_free(odb_object[0]);
@@ -286,7 +342,5 @@ void git_merge_file_result_free(git_merge_file_result *result)
 		return;
 
 	git__free((char *)result->path);
-
-	/* xdiff uses malloc() not git_malloc, so we use free(), not git_free() */
-	free((char *)result->ptr);
+	git__free((char *)result->ptr);
 }
diff --git a/src/merge_file.h b/src/merge_file.h
index 263391e..08ecfc0 100644
--- a/src/merge_file.h
+++ b/src/merge_file.h
@@ -7,8 +7,7 @@
 #ifndef INCLUDE_filediff_h__
 #define INCLUDE_filediff_h__
 
-#include "xdiff/xdiff.h"
-
-#include "git2/merge.h"
+/* xdiff cannot cope with large files, just treat them as binary */
+#define GIT_MERGE_FILE_XDIFF_MAX (1024UL * 1024 * 1023)
 
 #endif
diff --git a/src/xdiff/xdiff.h b/src/xdiff/xdiff.h
index e2f1e89..db5d598 100644
--- a/src/xdiff/xdiff.h
+++ b/src/xdiff/xdiff.h
@@ -20,6 +20,8 @@
  *
  */
 
+#include "util.h"
+
 #if !defined(XDIFF_H)
 #define XDIFF_H
 
@@ -106,9 +108,9 @@ typedef struct s_bdiffparam {
 } bdiffparam_t;
 
 
-#define xdl_malloc(x) malloc(x)
-#define xdl_free(ptr) free(ptr)
-#define xdl_realloc(ptr,x) realloc(ptr,x)
+#define xdl_malloc(x) git__malloc(x)
+#define xdl_free(ptr) git__free(ptr)
+#define xdl_realloc(ptr,x) git__realloc(ptr,x)
 
 void *xdl_mmfile_first(mmfile_t *mmf, long *size);
 long xdl_mmfile_size(mmfile_t *mmf);
diff --git a/tests/merge/files.c b/tests/merge/files.c
index 2fd90d0..b365d5a 100644
--- a/tests/merge/files.c
+++ b/tests/merge/files.c
@@ -3,6 +3,7 @@
 #include "git2/merge.h"
 #include "buffer.h"
 #include "merge.h"
+#include "merge_file.h"
 #include "merge_helpers.h"
 #include "refs.h"
 #include "fileops.h"
@@ -288,3 +289,90 @@ void test_merge_files__doesnt_add_newline(void)
 	git_merge_file_result_free(&result);
 }
 
+void test_merge_files__skips_large_files(void)
+{
+	git_merge_file_input ours = GIT_MERGE_FILE_INPUT_INIT,
+		theirs = GIT_MERGE_FILE_INPUT_INIT;
+	git_merge_file_options opts = GIT_MERGE_FILE_OPTIONS_INIT;
+	git_merge_file_result result = {0};
+
+	ours.size = GIT_MERGE_FILE_XDIFF_MAX + 1;
+	ours.path = "testfile.txt";
+	ours.mode = 0100755;
+
+	theirs.size = GIT_MERGE_FILE_XDIFF_MAX + 1;
+	theirs.path = "testfile.txt";
+	theirs.mode = 0100755;
+
+	cl_git_pass(git_merge_file(&result, NULL, &ours, &theirs, &opts));
+
+	cl_assert_equal_i(0, result.automergeable);
+
+	git_merge_file_result_free(&result);
+}
+
+void test_merge_files__skips_binaries(void)
+{
+	git_merge_file_input ancestor = GIT_MERGE_FILE_INPUT_INIT,
+		ours = GIT_MERGE_FILE_INPUT_INIT,
+		theirs = GIT_MERGE_FILE_INPUT_INIT;
+	git_merge_file_result result = {0};
+
+	ancestor.ptr = "ance\0stor\0";
+	ancestor.size = 10;
+	ancestor.path = "ancestor.txt";
+	ancestor.mode = 0100755;
+
+	ours.ptr = "foo\0bar\0";
+	ours.size = 8;
+	ours.path = "ours.txt";
+	ours.mode = 0100755;
+
+	theirs.ptr = "bar\0foo\0";
+	theirs.size = 8;
+	theirs.path = "theirs.txt";
+	theirs.mode = 0100644;
+
+	cl_git_pass(git_merge_file(&result, &ancestor, &ours, &theirs, NULL));
+
+	cl_assert_equal_i(0, result.automergeable);
+
+	git_merge_file_result_free(&result);
+}
+
+void test_merge_files__handles_binaries_when_favored(void)
+{
+	git_merge_file_input ancestor = GIT_MERGE_FILE_INPUT_INIT,
+		ours = GIT_MERGE_FILE_INPUT_INIT,
+		theirs = GIT_MERGE_FILE_INPUT_INIT;
+	git_merge_file_options opts = GIT_MERGE_FILE_OPTIONS_INIT;
+	git_merge_file_result result = {0};
+
+	ancestor.ptr = "ance\0stor\0";
+	ancestor.size = 10;
+	ancestor.path = "ancestor.txt";
+	ancestor.mode = 0100755;
+
+	ours.ptr = "foo\0bar\0";
+	ours.size = 8;
+	ours.path = "ours.txt";
+	ours.mode = 0100755;
+
+	theirs.ptr = "bar\0foo\0";
+	theirs.size = 8;
+	theirs.path = "theirs.txt";
+	theirs.mode = 0100644;
+
+	opts.favor = GIT_MERGE_FILE_FAVOR_OURS;
+	cl_git_pass(git_merge_file(&result, &ancestor, &ours, &theirs, &opts));
+
+	cl_assert_equal_i(1, result.automergeable);
+
+	cl_assert_equal_s("ours.txt", result.path);
+	cl_assert_equal_i(0100755, result.mode);
+
+	cl_assert_equal_i(ours.size, result.len);
+	cl_assert(memcmp(result.ptr, ours.ptr, ours.size) == 0);
+
+	git_merge_file_result_free(&result);
+}