abuild: rewrite hardlink handling when compressing man pages

The problem is that gzip refuses to run if it detects that a file has
more than 1 link. Our existing solution (removing hardlinks, compressing
the man page and recreating the hardlinks) made certain assumptions
about inode order that are only given on Unix v7 like filesystems
meaning it didn't work properly on 'tree-based' filesystems like BTRFS
or ZFS.

This patch has a different more bulletproof approach: It simply replaces
all hardlinks with symlinks. This is way easier because symlinks (unlike
hardlinks) can point to a file that doesn't exist, therefore we can
update all links before compressing the file in an easy way.

abuild.in

@@ -1407,29 +1407,33 @@ default_doc() {
 	done
 
 	# compress man pages
-	local previnode= prevname=  mandir="$subpkgdir"/usr/share/man
-	[ -d "$mandir" ] && find "$subpkgdir"/usr/share/man \
-		-type f \( -name \*.[0-8n] -o -name \*.[0-8][a-z]* \) \
-		-exec stat -c "%i %n" {} \; | sort -n \
-		| while read inode name; do
+	local mandir="$subpkgdir"/usr/share/man
+	[ -d "$mandir" ] && find "$mandir" -type f \
+		-a \( -name \*.[0-8n] -o -name \*.[0-8][a-z]* \) \
+		-exec stat -c "%i %n" \{\} \; | while read inode name; do
 
-		if [ "$inode" = "$previnode" ]; then
-			# update hard link
-			rm "$name"
-			ln "$prevname".gz "$name".gz
-		else
-			gzip -9 "$name"
-		fi
+		# Skip hardlinks removed in last iteration.
+		[ -f "$name" ] || continue
 
-		previnode="$inode"
-		prevname="$name"
+		local islink=0
+		find "$mandir" -type f -links +1 \
+			-a \( -name \*.[0-8n] -o -name \*.[0-8][a-z]* \) \
+			-exec stat -c "%i %n" \{\} \; | while read linode lname; do
+			if [ "$linode" = "$inode" -a "$lname" != "$name" ]; then
+				islink=1
+				rm -f "$lname"
+				ln -s "${name##*/}".gz "$lname".gz
+			fi
+		done
+
+		[ $islink -eq 0 ] && gzip -9 "$name"
 	done
-	[ -d "$mandir" ] && find "$subpkgdir"/usr/share/man \
-		-type l \( -name \*.[0-8n] -o -name \*.[0-8][a-z]* \) \
+	[ -d "$mandir" ] && find "$mandir" -type l \
+		-a \( -name \*.[0-8n] -o -name \*.[0-8][a-z]* \) \
 		| while read symlink; do
 
 		ln -s $(readlink $symlink).gz "$symlink".gz
-		rm "$symlink"
+		rm -f "$symlink"
 	done
 
 	rm -f "$subpkgdir/usr/share/info/dir"