read-cache: relocate and unexport commit_locked_index()

This function is now only used by write_locked_index(). Move it to
read-cache.c (because read-cache.c will need to be aware of
alternate_index_output later) and unexport it.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -552,7 +552,6 @@ extern int commit_lock_file(struct lock_file *);
 extern void update_index_if_able(struct index_state *, struct lock_file *);
 
 extern int hold_locked_index(struct lock_file *, int);
-extern int commit_locked_index(struct lock_file *);
 extern void set_alternate_index_output(const char *);
 extern int close_lock_file(struct lock_file *);
 extern void rollback_lock_file(struct lock_file *);

lockfile.c

@@ -5,7 +5,6 @@
 #include "sigchain.h"
 
 static struct lock_file *lock_file_list;
-static const char *alternate_index_output;
 
 static void remove_lock_file(void)
 {
@@ -252,25 +251,6 @@ int hold_locked_index(struct lock_file *lk, int die_on_error)
 					 : 0);
 }
 
-void set_alternate_index_output(const char *name)
-{
-	alternate_index_output = name;
-}
-
-int commit_locked_index(struct lock_file *lk)
-{
-	if (alternate_index_output) {
-		if (lk->fd >= 0 && close_lock_file(lk))
-			return -1;
-		if (rename(lk->filename, alternate_index_output))
-			return -1;
-		lk->filename[0] = 0;
-		return 0;
-	}
-	else
-		return commit_lock_file(lk);
-}
-
 void rollback_lock_file(struct lock_file *lk)
 {
 	if (lk->filename[0]) {

read-cache.c

@@ -36,6 +36,7 @@ static struct cache_entry *refresh_cache_entry(struct cache_entry *ce,
 #define CACHE_EXT_RESOLVE_UNDO 0x52455543 /* "REUC" */
 
 struct index_state the_index;
+static const char *alternate_index_output;
 
 static void set_index_entry(struct index_state *istate, int nr, struct cache_entry *ce)
 {
@@ -1875,6 +1876,25 @@ static int do_write_index(struct index_state *istate, int newfd)
 	return 0;
 }
 
+void set_alternate_index_output(const char *name)
+{
+	alternate_index_output = name;
+}
+
+static int commit_locked_index(struct lock_file *lk)
+{
+	if (alternate_index_output) {
+		if (lk->fd >= 0 && close_lock_file(lk))
+			return -1;
+		if (rename(lk->filename, alternate_index_output))
+			return -1;
+		lk->filename[0] = 0;
+		return 0;
+	} else {
+		return commit_lock_file(lk);
+	}
+}
+
 static int do_write_locked_index(struct index_state *istate, struct lock_file *lock,
 				 unsigned flags)
 {