Simplify rule to use regex instead of splitting

add check if there is actually a package manager in the run command

checks/docker/update_instruction_alone.rego

@@ -24,23 +24,23 @@ deny[res] {
 
 	command = concat(" ", run.Value)
 
+  is_package_manager(command)
 	is_valid_update(command)
 	not update_followed_by_install(command)
 
 	msg := "The instruction 'RUN <package-manager> update' should always be followed by '<package-manager> install' in the same RUN statement."
 	res := result.new(msg, run)
 }
 
-is_valid_update(command) {
-	chained_parts := regex.split(`\s*&&\s*`, command)
-
-	array_split := split(chained_parts[_], " ")
-
-	len = count(array_split)
+package_manager_regex := `(apk)|(apt-get)|(yum)`
 
-	update := {"update", "--update"}
+is_package_manager(command) {
+  regex.match(package_manager_regex, command)
+}
 
-	array_split[len - 1] == update[_]
+update_regex := `( update)|( check-update)`
+is_valid_update(command) {
+  regex.match(update_regex, command)
 }
 
 update_followed_by_install(command) {

checks/docker/update_instruction_alone_test.rego

@@ -77,16 +77,20 @@ test_allowed {
 		},
 		{
 			"Cmd": "run",
-			"Value": ["apt-get update     && apt-get install -y --no-install-recommends mysql-client     && rm -rf /var/lib/apt/lists/*"],
+			"Value": ["apt-get update && apt-get install -y --no-install-recommends mysql-client && rm -rf /var/lib/apt/lists/*"],
 		},
 		{
 			"Cmd": "run",
-			"Value": ["apk update     && apk add --no-cache git ca-certificates"],
+			"Value": ["apk update && apk add --no-cache git ca-certificates"],
 		},
 		{
 			"Cmd": "run",
 			"Value": ["apk --update add easy-rsa"],
 		},
+    {
+      "Cmd": "run",
+      "Value": ["/bin/sh /scripts/someScript.sh update"],
+    },
 		{
 			"Cmd": "entrypoint",
 			"Value": ["mysql"],