scripts/installer.sh: support DNF5

This fixes the installation on newer Fedora versions that use dnf5 as
the 'dnf' binary.

Updates #13828

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I39513243c81640fab244a32b7dbb3f32071e9fce

scripts/installer.sh

@@ -488,9 +488,41 @@ main() {
 			set +x
 		;;
 		dnf)
+			# DNF 5 has a different argument format; determine which one we have.
+			DNF_VERSION="3"
+			if dnf --version | grep -q '^dnf5 version'; then
+				DNF_VERSION="5"
+			fi
+
+			# The 'config-manager' plugin wasn't implemented when
+			# DNF5 was released; detect that and use the old
+			# version if necessary.
+			if [ "$DNF_VERSION" = "5" ]; then
+				set -x
+				$SUDO dnf install -y 'dnf-command(config-manager)' && DNF_HAVE_CONFIG_MANAGER=1 || DNF_HAVE_CONFIG_MANAGER=0
+				set +x
+
+				if [ "$DNF_HAVE_CONFIG_MANAGER" != "1" ]; then
+					if type dnf-3 >/dev/null; then
+						DNF_VERSION="3"
+					else
+						echo "dnf 5 detected, but 'dnf-command(config-manager)' not available and dnf-3 not found"
+						exit 1
+					fi
+				fi
+			fi
+
 			set -x
+			if [ "$DNF_VERSION" = "3" ]; then
 				$SUDO dnf install -y 'dnf-command(config-manager)'
 				$SUDO dnf config-manager --add-repo "https://pkgs.tailscale.com/$TRACK/$OS/$VERSION/tailscale.repo"
+			elif [ "$DNF_VERSION" = "5" ]; then
+				# Already installed config-manager, above.
+				$SUDO dnf config-manager addrepo --from-repofile="https://pkgs.tailscale.com/$TRACK/$OS/$VERSION/tailscale.repo"
+			else
+				echo "unexpected: unknown dnf version $DNF_VERSION"
+				exit 1
+			fi
 			$SUDO dnf install -y tailscale
 			$SUDO systemctl enable --now tailscaled
 			set +x