Add new packs input to init action

This input allows users to specify which packs to run. It works in
unison with the packs block of the config file and it is similar to
how `queries` works. They both use `+` in the same way.

Note that the `#TODO` in the pr check is still around, but the CLI
is available. I will remove the TODO in the next commit.

src/config-utils.ts

@@ -585,13 +585,15 @@ export function getPacksInvalid(configFile: string): string {
 
 export function getPacksStrInvalid(
   packStr: string,
-  configFile: string
+  configFile?: string
 ): string {
-  return getConfigFilePropertyError(
-    configFile,
-    PACKS_PROPERTY,
-    `"${packStr}" is not a valid pack`
-  );
+  return configFile
+    ? getConfigFilePropertyError(
+        configFile,
+        PACKS_PROPERTY,
+        `"${packStr}" is not a valid pack`
+      )
+    : `"${packStr}" is not a valid pack`;
 }
 
 export function getLocalPathOutsideOfRepository(
@@ -802,6 +804,7 @@ function shouldAddConfigFileQueries(queriesInput: string | undefined): boolean {
 export async function getDefaultConfig(
   languagesInput: string | undefined,
   queriesInput: string | undefined,
+  packsInput: string | undefined,
   dbLocation: string | undefined,
   repository: RepositoryNwo,
   tempDir: string,
@@ -840,12 +843,14 @@ export async function getDefaultConfig(
     );
   }
 
+  const packs = parsePacksInput(packsInput, languages) ?? {};
+
   return {
     languages,
     queries,
     pathsIgnore: [],
     paths: [],
-    packs: {},
+    packs,
     originalUserInput: {},
     tempDir,
     toolCacheDir,
@@ -861,6 +866,7 @@ export async function getDefaultConfig(
 async function loadConfig(
   languagesInput: string | undefined,
   queriesInput: string | undefined,
+  packsInput: string | undefined,
   configFile: string,
   dbLocation: string | undefined,
   repository: RepositoryNwo,
@@ -1002,6 +1008,7 @@ async function loadConfig(
 
   const packs = parsePacks(
     parsedYAML[PACKS_PROPERTY] ?? {},
+    packsInput,
     languages,
     configFile
   );
@@ -1033,7 +1040,7 @@ const PACK_IDENTIFIER_PATTERN = (function () {
 })();
 
 // Exported for testing
-export function parsePacks(
+export function parsePacksFromConfig(
   packsByLanguage: string[] | Record<string, string[]>,
   languages: Language[],
   configFile: string
@@ -1068,12 +1075,44 @@ export function parsePacks(
   return packs;
 }
 
-function toPackWithVersion(packStr, configFile: string): PackWithVersion {
+function parsePacksInput(
+  packsInput: string | undefined,
+  languages: Language[]
+): Packs | undefined {
+  if (!packsInput?.trim()) {
+    return undefined;
+  }
+
+  if (languages.length > 1) {
+    throw new Error(
+      "Cannot specify a 'packs' input in a multi-language analysis. Use a codeql-config.yml file instead and specify packs by library."
+    );
+  } else if (languages.length === 0) {
+    throw new Error("No languages specified. Cannot process the packs input.");
+  }
+
+  packsInput = packsInput.trim();
+  if (packsInput.startsWith("+")) {
+    packsInput = packsInput.substring(1).trim();
+    if (!packsInput) {
+      throw new Error("Remove the '+' from the packs input.");
+    }
+  }
+
+  return {
+    [languages[0]]: packsInput.split(",").reduce((packs, pack) => {
+      packs.push(toPackWithVersion(pack, ""));
+      return packs;
+    }, [] as PackWithVersion[]),
+  };
+}
+
+function toPackWithVersion(packStr, configFile?: string): PackWithVersion {
   if (typeof packStr !== "string") {
     throw new Error(getPacksStrInvalid(packStr, configFile));
   }
 
-  const nameWithVersion = packStr.split("@");
+  const nameWithVersion = packStr.trim().split("@");
   let version: string | undefined;
   if (
     nameWithVersion.length > 2 ||
@@ -1088,11 +1127,52 @@ function toPackWithVersion(packStr, configFile: string): PackWithVersion {
   }
 
   return {
-    packName: nameWithVersion[0],
+    packName: nameWithVersion[0].trim(),
     version,
   };
 }
 
+// exported for testing
+export function parsePacks(
+  rawPacksFromConfig: string[] | Record<string, string[]>,
+  rawPacksInput: string | undefined,
+  languages: Language[],
+  configFile: string
+) {
+  const packsFromInput = parsePacksInput(rawPacksInput, languages);
+  const packsFomConfig = parsePacksFromConfig(
+    rawPacksFromConfig,
+    languages,
+    configFile
+  );
+
+  if (!packsFromInput) {
+    return packsFomConfig;
+  }
+  if (!shouldCombinePacks(rawPacksInput)) {
+    return packsFromInput;
+  }
+
+  return combinePacks(packsFromInput, packsFomConfig);
+}
+
+function shouldCombinePacks(packsInput?: string): boolean {
+  return !!packsInput?.trim().startsWith("+");
+}
+
+function combinePacks(packs1: Packs, packs2: Packs): Packs {
+  const packs = {};
+  for (const lang of Object.keys(packs1)) {
+    packs[lang] = packs1[lang].concat(packs2[lang] || []);
+  }
+  for (const lang of Object.keys(packs2)) {
+    if (!packs[lang]) {
+      packs[lang] = packs2[lang];
+    }
+  }
+  return packs;
+}
+
 function dbLocationOrDefault(
   dbLocation: string | undefined,
   tempDir: string
@@ -1109,6 +1189,7 @@ function dbLocationOrDefault(
 export async function initConfig(
   languagesInput: string | undefined,
   queriesInput: string | undefined,
+  packsInput: string | undefined,
   configFile: string | undefined,
   dbLocation: string | undefined,
   repository: RepositoryNwo,
@@ -1128,6 +1209,7 @@ export async function initConfig(
     config = await getDefaultConfig(
       languagesInput,
       queriesInput,
+      packsInput,
       dbLocation,
       repository,
       tempDir,
@@ -1142,6 +1224,7 @@ export async function initConfig(
     config = await loadConfig(
       languagesInput,
       queriesInput,
+      packsInput,
       configFile,
       dbLocation,
       repository,