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

@@ -15,35 +15,52 @@ const args = process.argv.slice(3);
 yargs
   .usage('Usage: $0 <command> [options>')
   .command(
-    'affected <action>',
+    'affected <apps|build|e2e|dep-graph>',
     'Compute affected applications',
     yargs =>
       yargs
-        .positional('action', {
-          choices: ['apps', 'build', 'e2e', 'dep-graph']
+        .option('files', {
+          type: 'array',
+          group: 'Compute apps affected by:',
+          describe: 'Specified files'
+        })
+        .option('uncommitted', {
+          group: 'Compute apps affected by:',
+          describe: 'Uncommitted changes'
+        })
+        .option('untracked', {
+          group: 'Compute apps affected by:',
+          describe: 'Untracked changes'
+        })
+        .option('SHAs', {
+          type: 'array',
+          group: 'Compute apps affected by:',
+          describe: 'Files changed between two SHAs'
         })
-        .command('<action> -- <SHA1 SHA2>', 'Targets within a range of SHAs')
         .command(
-          '<action> -- files="<file,list>"',
-          'Targets a comma delimited list of files'
+          '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('<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', [
@@ -55,17 +72,12 @@ yargs
             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);
-    }
+        .conflicts({
+          files: ['uncommitted', 'untracked', 'SHAs'],
+          untracked: ['uncommitted', 'files', 'SHAs'],
+          SHAs: ['uncommitted', 'untracked', 'files'],
+          uncommitted: ['files', 'untracked', 'SHAs']
+        })
   )
   .command(
     'format <write|check>',
@@ -81,19 +93,19 @@ yargs
   .command(
     // TODO: delete this after 1.0
     'update <check|skip>',
-    'Migrate to the latest version of NX',
+    'Update to the latest version of Nx',
     yargs =>
       yargs
-        .describe('check', 'Check if there are migrations to run')
-        .describe('skip', 'Skip running the latest set of migrations'),
+        .describe('check', 'Check if there are Nx updates to run')
+        .describe('skip', 'Skip running the latest set of Nx updates'),
     _ => {
       update(args);
     }
   )
   .alias('update', 'migrates') // TODO: Remove after 1.0
   .command(
     'lint [files..]',
-    'Line workspace or set of files',
+    'Lint workspace or set of files',
     yargs => yargs,
     _ => {
       lint();
@@ -110,7 +122,7 @@ yargs
   )
   .command(
     'workspace-schematic <name>',
-    'Generate a schematic `ng g <name>`',
+    'Generate a custom schematic that can be run via `ng g <name>`',
     yargs =>
       yargs.positional('name', {
         type: 'string',
@@ -122,5 +134,5 @@ yargs
   )
   .help('help')
   .version(false)
-  .strict()
+  .showHelpOnFail(true)
   .demandCommand().argv; // .argv bootstraps the CLI creation;