Rename files and headers related to index AM

The following renaming is done so as source files related to index
access methods are more consistent with table access methods (the
original names used for index AMs ware too generic, and could be
confused as including features related to table AMs):
- amapi.h -> indexam.h.
- amapi.c -> indexamapi.c.  Here we have an equivalent with
backend/access/table/tableamapi.c.
- amvalidate.c -> indexamvalidate.c.
- amvalidate.h -> indexamvalidate.h.
- genam.c -> indexgenam.c.
- genam.h -> indexgenam.h.

This has been discussed during the development of v12 when table AM was
worked on, but the renaming never happened.

Author: Michael Paquier
Reviewed-by: Fabien Coelho, Julien Rouhaud
Discussion: https://postgr.es/m/20191223053434.GF34339@paquier.xyz

src/backend/access/index/Makefile

@@ -13,9 +13,9 @@ top_builddir = ../../../..
 include $(top_builddir)/src/Makefile.global
 
 OBJS = \
-	amapi.o \
-	amvalidate.o \
-	genam.o \
-	indexam.o
+	indexam.o \
+	indexamapi.o \
+	indexamvalidate.o \
+	indexgenam.o
 
 include $(top_srcdir)/src/backend/common.mk

src/backend/access/index/indexam.c

@@ -43,8 +43,8 @@
 
 #include "postgres.h"
 
-#include "access/amapi.h"
 #include "access/heapam.h"
+#include "access/indexam.h"
 #include "access/relscan.h"
 #include "access/tableam.h"
 #include "access/transam.h"

src/backend/access/index/indexamapi.c

@@ -1,20 +1,20 @@
 /*-------------------------------------------------------------------------
  *
- * amapi.c
+ * indexamapi.c
  *	  Support routines for API for Postgres index access methods.
  *
  * Copyright (c) 2015-2019, PostgreSQL Global Development Group
  *
  *
  * IDENTIFICATION
- *	  src/backend/access/index/amapi.c
+ *	  src/backend/access/index/indexamapi.c
  *
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
 
-#include "access/amapi.h"
 #include "access/htup_details.h"
+#include "access/indexam.h"
 #include "catalog/pg_am.h"
 #include "catalog/pg_opclass.h"
 #include "utils/builtins.h"

src/backend/access/index/indexamvalidate.c

@@ -1,20 +1,20 @@
 /*-------------------------------------------------------------------------
  *
- * amvalidate.c
+ * indexamvalidate.c
  *	  Support routines for index access methods' amvalidate functions.
  *
  * Copyright (c) 2016-2019, PostgreSQL Global Development Group
  *
  *
  * IDENTIFICATION
- *	  src/backend/access/index/amvalidate.c
+ *	  src/backend/access/index/indexamvalidate.c
  *
  *-------------------------------------------------------------------------
  */
 #include "postgres.h"
 
-#include "access/amvalidate.h"
 #include "access/htup_details.h"
+#include "access/indexamvalidate.h"
 #include "catalog/pg_am.h"
 #include "catalog/pg_amop.h"
 #include "catalog/pg_amproc.h"

src/backend/access/index/indexgenam.c

@@ -1,6 +1,6 @@
 /*-------------------------------------------------------------------------
  *
- * genam.c
+ * indexgenam.c
  *	  general index access method routines
  *
  * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
@@ -8,19 +8,19 @@
  *
  *
  * IDENTIFICATION
- *	  src/backend/access/index/genam.c
+ *	  src/backend/access/index/indexgenam.c
  *
  * NOTES
  *	  many of the old access method routines have been turned into
- *	  macros and moved to genam.h -cim 4/30/91
+ *	  macros and moved to indexgenam.h -cim 4/30/91
  *
  *-------------------------------------------------------------------------
  */
 
 #include "postgres.h"
 
-#include "access/genam.h"
 #include "access/heapam.h"
+#include "access/indexgenam.h"
 #include "access/relscan.h"
 #include "access/tableam.h"
 #include "access/transam.h"