refs.c: don't expose the internal struct ref_lock in the header file

Now the struct ref_lock is used completely internally, so let's
remove it from the header file.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -6,6 +6,15 @@
 #include "dir.h"
 #include "string-list.h"
 
+struct ref_lock {
+	char *ref_name;
+	char *orig_ref_name;
+	struct lock_file *lk;
+	unsigned char old_sha1[20];
+	int lock_fd;
+	int force_write;
+};
+
 /*
  * How to handle various characters in refnames:
  * 0: An acceptable character for refs

refs.h

@@ -1,15 +1,6 @@
 #ifndef REFS_H
 #define REFS_H
 
-struct ref_lock {
-	char *ref_name;
-	char *orig_ref_name;
-	struct lock_file *lk;
-	unsigned char old_sha1[20];
-	int lock_fd;
-	int force_write;
-};
-
 /*
  * A ref_transaction represents a collection of ref updates
  * that should succeed or fail together.