merge.h: move declarations for merge.c from cache.h

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

merge.h

@@ -0,0 +1,17 @@
+#ifndef MERGE_H
+#define MERGE_H
+
+struct commit_list;
+struct object_id;
+struct repository;
+
+int try_merge_command(struct repository *r,
+		const char *strategy, size_t xopts_nr,
+		const char **xopts, struct commit_list *common,
+		const char *head_arg, struct commit_list *remotes);
+int checkout_fast_forward(struct repository *r,
+			  const struct object_id *from,
+			  const struct object_id *to,
+			  int overwrite_ignore);
+
+#endif /* MERGE_H */