Automatically setup apk repositories if not specified

Configure network repositories with setup-apkrepos if no repositories
file exists.

lib/tiny-cloud/user-data/alpine-config

@@ -172,6 +172,11 @@ init__userdata_apk_cache() {
 }
 
 init__userdata_apk_repositories() {
+	local apk="$(get_userdata apk)"
+	if [ -z "$apk" ] && ! [ -e "$ROOT"/etc/apk/repositories ]; then
+		$MOCK setup-apkrepos -1 -c
+		return
+	fi
 	local repositories="$(get_userdata apk/repositories)"
 	mkdir -p "$ROOT"/etc/apk
 	for r in $repositories; do

tests/tiny-cloud-alpine.test

@@ -22,6 +22,7 @@ init_tests \
 	userdata_ntp_busybox \
 	userdata_ntp_openntpd \
 	userdata_apk_cache \
+	userdata_apk_empty \
 	userdata_apk_repositories \
 	userdata_apk_repositories_version \
 	userdata_apk_repositories_version_auto_edge \
@@ -238,6 +239,17 @@ userdata_apk_cache_body() {
 	atf_check -o match:"$PWD/var/cache/apk" readlink -f etc/apk/cache
 }
 
+userdata_apk_empty_body() {
+	fake_userdata_nocloud <<-EOF
+		#alpine-config
+	EOF
+	atf_check -e ignore -o ignore tiny-cloud early
+	atf_check \
+		-e match:"userdata_apk_repositories: done" \
+		-o match:"setup-apkrepos -1 -c" \
+		tiny-cloud main
+}
+
 userdata_apk_repositories_body() {
 	fake_userdata_nocloud <<-EOF
 		#alpine-config