Split the release notes into a separate file for each (active) major branch,

as per my recent proposal.  release.sgml itself is now just a stub that should
change rarely; ideally, only once per major release to add a new include line.
Most editing work will occur in the release-N.N.sgml files.  To update a back
branch for a minor release, just copy the appropriate release-N.N.sgml
file(s) into the back branch.

This commit doesn't change the end-product documentation at all, only the
source layout.  However, it makes it easy to start omitting ancient information
from newer branches' documentation, should we ever decide to do that.

doc/src/sgml/Makefile

@@ -2,7 +2,7 @@
 #
 # PostgreSQL documentation makefile
 #
-# $PostgreSQL: pgsql/doc/src/sgml/Makefile,v 1.114 2008/12/11 07:34:07 petere Exp $
+# $PostgreSQL: pgsql/doc/src/sgml/Makefile,v 1.115 2009/05/02 20:17:19 tgl Exp $
 #
 #----------------------------------------------------------------------------
 
@@ -208,12 +208,8 @@ INSTALL HISTORY regress_README: % : %.html
 INSTALL.html: standalone-install.sgml installation.sgml version.sgml
 	$(JADE.text) -V nochunks standalone-install.sgml installation.sgml >$@
 
-# remove links to main documentation
-HISTORY.html: release.sgml
-	( echo '<!doctype appendix PUBLIC "-//OASIS//DTD DocBook V4.2//EN">'; \
-	  cat $< ) | \
-	$(PERL) -p -0 -e 's/<link\s+linkend[^>]*>//g' | \
-	$(PERL) -p -e 's/<\/link>//g' >tempfile_HISTORY.sgml
+HISTORY.html: generate_history.pl $(wildcard $(srcdir)/release*.sgml)
+	$(PERL) $< "$(srcdir)" release.sgml >tempfile_HISTORY.sgml
 	$(JADE.text) -V nochunks tempfile_HISTORY.sgml >$@
 	rm tempfile_HISTORY.sgml
 

doc/src/sgml/filelist.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/filelist.sgml,v 1.60 2009/03/25 23:20:01 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/filelist.sgml,v 1.61 2009/05/02 20:17:19 tgl Exp $ -->
 
 <!entity history    SYSTEM "history.sgml">
 <!entity info       SYSTEM "info.sgml">
@@ -138,7 +138,16 @@
 <!entity errcodes   SYSTEM "errcodes.sgml">
 <!entity features   SYSTEM "features.sgml">
 <!entity keywords   SYSTEM "keywords.sgml">
+
 <!entity release    SYSTEM "release.sgml">
+<!entity release-8.4    SYSTEM "release-8.4.sgml">
+<!entity release-8.3    SYSTEM "release-8.3.sgml">
+<!entity release-8.2    SYSTEM "release-8.2.sgml">
+<!entity release-8.1    SYSTEM "release-8.1.sgml">
+<!entity release-8.0    SYSTEM "release-8.0.sgml">
+<!entity release-7.4    SYSTEM "release-7.4.sgml">
+<!entity release-old    SYSTEM "release-old.sgml">
+
 <!entity acronyms   SYSTEM "acronyms.sgml">
 
 <!entity features-supported   SYSTEM "features-supported.sgml">

doc/src/sgml/generate_history.pl

@@ -0,0 +1,58 @@
+#! /usr/bin/perl -w
+
+# generate_history.pl -- flatten release notes for use as HISTORY file
+#
+# Usage: generate_history.pl srcdir release.sgml >output.sgml
+#
+# The main point of this script is to strip out <link> references, which
+# generally point into the rest of the documentation and so can't be used
+# in a standalone build of the release notes.  To make sure this is done
+# everywhere, we have to fold in the sub-files of the release notes.
+#
+# $PostgreSQL: pgsql/doc/src/sgml/generate_history.pl,v 1.1 2009/05/02 20:17:19 tgl Exp $
+
+use strict;
+
+my($srcdir) = shift;
+defined($srcdir) || die "$0: missing required argument: srcdir\n";
+my($infile) = shift;
+defined($infile) || die "$0: missing required argument: inputfile\n";
+
+# Emit DOCTYPE header so that the output is a self-contained SGML document
+print "<!DOCTYPE appendix PUBLIC \"-//OASIS//DTD DocBook V4.2//EN\">\n";
+
+process_file($infile);
+
+exit 0;
+
+sub process_file {
+    my($filename) = @_;
+
+    local *FILE;		# need a local filehandle so we can recurse
+
+    my($f) = $srcdir . '/' . $filename;
+    open(FILE, $f) || die "could not read $f: $!\n";
+
+    while (<FILE>) {
+	# Recursively expand sub-files of the release notes
+	if (m/^&(release-.*);$/) {
+	    process_file($1 . ".sgml");
+	    next;
+	}
+
+	# Remove <link ...> tags, which might span multiple lines
+	while (m/<link/) {
+	    if (s/<link\s+linkend[^>]*>//) {
+		next;
+	    }
+	    # incomplete tag, so slurp another line
+	    $_ .= <FILE>;
+	}
+
+	# Remove </link> too
+	s|</link>||g;
+
+	print;
+    }
+    close(FILE);
+}