[PATCH v5 05/12] merge-index: don't fork if the requested program is `git-merge-one-file'

@@ -1,11 +1,15 @@
 #define USE_THE_INDEX_COMPATIBILITY_MACROS
 #include "builtin.h"
+#include "lockfile.h"
 #include "merge-strategies.h"
 
 int cmd_merge_index(int argc, const char **argv, const char *prefix)
 {
 	int i, force_file = 0, err = 0, one_shot = 0, quiet = 0;
 	const char *pgm;
+	void *data;
+	merge_fn merge_action;
+	struct lock_file lock = LOCK_INIT;
 
 	/* Without this we cannot rely on waitpid() to tell
 	 * what happened to our children.

@@ -26,7 +30,19 @@ int cmd_merge_index(int argc, const char **argv, const char *prefix)
 		quiet = 1;
 		i++;
 	}
+
 	pgm = argv[i++];
+	if (!strcmp(pgm, "git-merge-one-file")) {
+		merge_action = merge_one_file_func;
+		data = (void *)the_repository;
+
+		setup_work_tree();
+		hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
+	} else {
+		merge_action = merge_one_file_spawn;
+		data = (void *)pgm;
+	}
+
 	for (; i < argc; i++) {
 		const char *arg = argv[i];
 		if (!force_file && *arg == '-') {

@@ -36,13 +52,22 @@ int cmd_merge_index(int argc, const char **argv, const char *prefix)
 			}
 			if (!strcmp(arg, "-a")) {
 				err |= merge_all_index(&the_index, one_shot, quiet,
-						       merge_one_file_spawn, (void *)pgm);
+						       merge_action, data);
 				continue;
 			}
 			die("git merge-index: unknown option %s", arg);
 		}
 		err |= merge_index_path(&the_index, one_shot, quiet, arg,
-					merge_one_file_spawn, (void *)pgm);
+					merge_action, data);
+	}
+
+	if (merge_action == merge_one_file_func) {
+		if (err) {
+			rollback_lock_file(&lock);
+			return err;
+		}
+
+		return write_locked_index(&the_index, &lock, COMMIT_LOCK);
 	}
 	return err;
 }

@@ -176,6 +176,17 @@ int merge_three_way(struct repository *r,
 	return 0;
 }
 
+int merge_one_file_func(const struct object_id *orig_blob,
+			const struct object_id *our_blob,
+			const struct object_id *their_blob, const char *path,
+			unsigned int orig_mode, unsigned int our_mode, unsigned int their_mode,
+			void *data)
+{
+	return merge_three_way((struct repository *)data,
+			       orig_blob, our_blob, their_blob, path,
+			       orig_mode, our_mode, their_mode);
+}
+
 int merge_one_file_spawn(const struct object_id *orig_blob,
 			 const struct object_id *our_blob,
 			 const struct object_id *their_blob, const char *path,

@@ -15,6 +15,12 @@ typedef int (*merge_fn)(const struct object_id *orig_blob,
 			unsigned int orig_mode, unsigned int our_mode, unsigned int their_mode,
 			void *data);
 
+int merge_one_file_func(const struct object_id *orig_blob,
+			const struct object_id *our_blob,
+			const struct object_id *their_blob, const char *path,
+			unsigned int orig_mode, unsigned int our_mode, unsigned int their_mode,
+			void *data);
+
 int merge_one_file_spawn(const struct object_id *orig_blob,
 			 const struct object_id *our_blob,
 			 const struct object_id *their_blob, const char *path,