repo-remove: create empty DB when all packages are removed

Rather than creating no database at all, create an empty zipped tar archive
in its place. This keeps the download side of repositories a bit more sane
as a DB will always exist, and pacman handles this empty case just fine.

For this to be fully transparent, we also need to make sure repo-add and
repo-remove accept an empty "DB" as an argument, which in reality is a
completely void of files .tar.{gz,bz2,xz} archive.

Signed-off-by: Dan McGee <dan@archlinux.org>

scripts/repo-add.sh.in

@@ -306,10 +306,15 @@ check_repo_db()
 	fi
 
 	if [ -f "$REPO_DB_FILE" ]; then
-		if ! bsdtar -tqf "$REPO_DB_FILE" '*/desc' 2>&1 >/dev/null; then
+		# there are two situations we can have here- a DB with some entries,
+		# or a DB with no contents at all.
+		if ! bsdtar -tqf "$REPO_DB_FILE" '*/desc' >/dev/null 2>&1; then
+			# check empty case
+			if [ -n "$(bsdtar -tqf "$REPO_DB_FILE" '*' 2>/dev/null)" ]; then
 				error "$(gettext "Repository file '%s' is not a proper pacman database.")" "$REPO_DB_FILE"
 				exit 1
 			fi
+		fi
 		msg "$(gettext "Extracting database to a temporary location...")"
 		bsdtar -xf "$REPO_DB_FILE" -C "$tmpdir"
 	else
@@ -484,8 +489,9 @@ if [ $success -eq 1 ]; then
 	if [ -n "$(ls)" ]; then
 		bsdtar -c${TAR_OPT}f "$filename" *
 	else
-		# the database will be moved to .old below, and there will be no new one to replace it
+		# we have no packages remaining? zip up some emptyness
-		error "$(gettext "All packages have been removed from the database. Deleting '%s'.")" "$REPO_DB_FILE"
+		warning "$(gettext "No packages remain, creating empty database.")"
+		bsdtar -c${TAR_OPT}f "$filename" -T /dev/null
 	fi
 	cd "$startdir"