Patch from Ian Campbell <ijc@hellion.org.uk>:

Detect duplicates in the extra images used for installation

Several files included under install.{386,amd} are actually identical to
others. Rather than duplicating them attempt to detect this and hardlink
them.

Since images can be downloaded from the web at build time it is not
always possible to detect identical files by looking for the symlinks
created by the debian-installer build. Instead we pass a list of
potential "doppelgangers" to extra_image each of which is checked for
similarity to the new image.

I added gtk/vmlinuz (which is always the same as plain vmlinuz) which
although not necessary makes it more explicit which kernel goes with the
initrd at very little cost.

Hardlinks are used in preference to symlinks since these are expected to
work better with isolinux and the Xen tools.

debian/changelog

@@ -30,6 +30,10 @@ debian-cd (3.1.4) UNRELEASED; urgency=low
     are at least as new as the jigdo files, as this helps people mirroring.
     Closes: #587774
 
+  [ Ian Campbell ]
+  * boot-x86: detect duplicates in the extra images used for installation
+    and replace with hard links.
+
  -- Steve McIntyre <93sam@debian.org>  Tue, 27 Feb 2010 12:24:29 +0100
 
 debian-cd (3.1.3) unstable; urgency=low

tools/boot/squeeze/boot-x86

@@ -133,6 +133,7 @@ fi
 
 extra_image () {
 	image=$1
+	doppelgangers="$2"
 	dir=$(dirname "$image")
 
 	mkdir -p $CDDIR/$INSTALLDIR/$dir
@@ -146,6 +147,14 @@ extra_image () {
 			wget "$DI_WWW_HOME/cdrom/$image" -O $CDDIR/$INSTALLDIR/"$image"
 		fi
 	fi
+	for doppelganger in $doppelgangers ; do
+		if [ -f "$CDDIR/$INSTALLDIR/$dir/$doppelganger" ] &&
+			cmp -s $CDDIR/$INSTALLDIR/"$image" $CDDIR/$INSTALLDIR/"$dir"/"$doppelganger" ; then
+			echo "  $image identical to $doppelganger. Linking"
+			ln -nf "$doppelganger" $CDDIR/$INSTALLDIR/"$image"
+			break
+		fi
+	done
 }
 
 # If multiple desktops are to be supported, set the default one
@@ -231,7 +240,8 @@ if [ "$THISTYPE" = "isolinux" ]; then
 	fi
 
 	if [ -e boot$N/isolinux/f3.txt.withgtk ]; then
-		extra_image gtk/initrd.gz
+		extra_image gtk/vmlinuz         "../vmlinuz"
+		extra_image gtk/initrd.gz       "../initrd.gz"
 		mv boot$N/isolinux/f3.txt.withgtk boot$N/isolinux/f3.txt
 		mv boot$N/isolinux/f4.txt.withgtk boot$N/isolinux/f4.txt
 		if [ -e boot$N/isolinux/isolinux.cfg.withgtk ]; then
@@ -243,8 +253,8 @@ if [ "$THISTYPE" = "isolinux" ]; then
 	rm -f boot$N/isolinux/isolinux.cfg.with*
 
 	if variant_enabled "xen" ; then
-		extra_image xen/vmlinuz
-		extra_image xen/initrd.gz
+		extra_image xen/vmlinuz         "../vmlinuz   ../gtk/vmlinuz"
+		extra_image xen/initrd.gz       "../initrd.gz ../gtk/initrd.gz"
 		extra_image xen/xm-debian.cfg
 	fi