feat(schematics): Generate --help for every CLI function.

    This PR introduces the yargs package as our CLI command handler.
    We build up commands using yargs to take advantage of its built
    in --help flag formatter.

packages/schematics/src/command-line/affected.ts

@@ -11,6 +11,7 @@ export function affected(args: string[]): void {
   let apps: string[];
   let projects: string[];
   let rest: string[];
+
   try {
     const p = parseFiles(args.slice(1));
     rest = p.rest;
@@ -38,15 +39,6 @@ export function affected(args: string[]): void {
 }
 
 function printError(command: string, e: any) {
-  console.error(
-    `Pass the SHA range, as follows: npm run affected:${command} -- SHA1 SHA2.`
-  );
-  console.error(
-    `Or pass the list of files, as follows: npm run affected:${command} -- --files="libs/mylib/index.ts,libs/mylib2/index.ts".`
-  );
-  console.error(
-    `Or to get the list of files from local changes: npm run affected:${command} -- --uncommitted | --untracked.`
-  );
   console.error(e.message);
 }
 

packages/schematics/src/command-line/nx.ts

@@ -14,58 +14,64 @@ const args = process.argv.slice(3);
 
 yargs
   .usage('Usage: $0 <command> [options>')
-  .command(
-    'affected <action>',
-    'Compute affected applications',
-    yargs =>
-      yargs
-        .positional('action', {
-          choices: ['apps', 'build', 'e2e', 'dep-graph']
-        })
-        .command('<action> -- <SHA1 SHA2>', 'Targets within a range of SHAs')
-        .command(
-          '<action> -- files="<file,list>"',
-          'Targets a comma delimited list of files'
-        )
-        .command('<action> -- --uncommitted', 'Targets uncommited changes')
-        .command('<action> -- --untracked', 'Targets untracked changes')
-        .demandCommand()
-        .command(
-          'dep-graph',
-          'Generate a graph showing links between targets',
-          yargs =>
-            yargs
-              .describe('file', 'output file (e.g. --file=.vis/output.json)')
-              .command('-- <SHA1 SHA2>', 'Targets within a range of SHAs')
-              .command(
-                '-- files="<file,list>"',
-                'Targets a comma delimited list of files'
-              )
-              .command('-- --uncommitted', 'Targets uncommited changes')
-              .command('-- --untracked', 'Targets untracked changes')
-              .demandCommand()
-              .demand('file')
-              .demand('output')
-              .choices('output', [
-                OutputType.json,
-                OutputType.dot,
-                OutputType.html
-              ]),
-          _ => {
-            generateGraph(yargsParser(args));
-          }
-        )
-        .demandCommand()
-        .describe('args', 'Prints the names of the affected apps')
-        .describe('build', 'Builds the affected apps')
-        .describe('e2e', 'Tests the affected apps')
-        .describe(
-          'dep-graph',
-          'Generate a graph showing links between apps and libs'
-        ),
-    _ => {
-      affected(args);
-    }
+  .command('affected', 'Compute affected applications', yargs =>
+    yargs
+      .option('files', {
+        type: 'array',
+        group: 'target',
+        describe: 'Files in for which affected targets will be computed'
+      })
+      .option('uncommitted', {
+        type: 'boolean',
+        group: 'target',
+        describe: 'Compute targets for uncommitted changes'
+      })
+      .option('untracked', {
+        type: 'boolean',
+        group: 'target',
+        describe: 'Compute targets for untracked changes'
+      })
+      .option('SHAs', {
+        type: 'string',
+        group: 'target',
+        describe: 'Compute targets changed between two SHAs'
+      })
+      .command(
+        'apps',
+        'Prints the names of the affected apps',
+        yargs => yargs,
+        () => affected(args)
+      )
+      .command(
+        'build',
+        'Builds the affected apps',
+        yargs => yargs,
+        () => affected(args)
+      )
+      .command(
+        'e2e',
+        'Tests the affected apps',
+        yargs => yargs,
+        () => affected(args)
+      )
+      .command(
+        'dep-graph',
+        'Generate a graph showing links between targets',
+        yargs =>
+          yargs
+            .describe('file', 'output file (e.g. --file=.vis/output.json)')
+            .demand('file')
+            .demand('output')
+            .choices('output', [
+              OutputType.json,
+              OutputType.dot,
+              OutputType.html
+            ]),
+        _ => {
+          generateGraph(yargsParser(args));
+        }
+      )
+      .demandCommand()
   )
   .command(
     'format <write|check>',
@@ -122,5 +128,5 @@ yargs
   )
   .help('help')
   .version(false)
-  .strict()
+  .showHelpOnFail(true)
   .demandCommand().argv; // .argv bootstraps the CLI creation;