Revert "Revert "Show help on no command" (webpack#276)"

This reverts commit 4079570.

bin/webpack.js

@@ -205,7 +205,6 @@
 				"Controls the output of lifecycle messaging e.g. Started watching files..."
 		}
 	});
-
 	// yargs will terminate the process early when the user uses help or version.
 	// This causes large help outputs to be cut short (https://github.com/nodejs/node/wiki/API-changes-between-v0.10-and-v4#process).
 	// To prevent this we use the yargs.parse API and exit the process normally
@@ -465,9 +464,12 @@
 				if (err) {
 					lastHash = null;
 					console.error(err.stack || err);
-					if (err.details) console.error(err.details);
-					process.exit(1); // eslint-disable-line
+					if (err.details) {
+						console.error(err.details);
+					}
+					process.exit(1);
 				}
+
 				if (outputOptions.json) {
 					stdout.write(
 						JSON.stringify(stats.toJson(outputOptions), null, 2) + "\n"
@@ -477,10 +479,20 @@
 					const statsString = stats.toString(outputOptions);
 					if (statsString) stdout.write(statsString + "\n");
 				}
+
 				if (!options.watch && stats.hasErrors()) {
 					process.exitCode = 2;
+
+					const fs = require("fs");
+					const context = stats.compilation.compiler.context;
+					const configPath = context + "/webpack.config.js";
+					const configMissing = !fs.existsSync(configPath);
+					if (yargs.argv._.length === 0 && configMissing) {
+						yargs.showHelp("log");
+					}
 				}
 			}
+
 			if (firstOptions.watch || options.watch) {
 				const watchOptions =
 					firstOptions.watchOptions ||
@@ -496,7 +508,9 @@
 				compiler.watch(watchOptions, compilerCallback);
 				if (outputOptions.infoVerbosity !== "none")
 					console.log("\nWebpack is watching the files…\n");
-			} else compiler.run(compilerCallback);
+			} else {
+				compiler.run(compilerCallback);
+			}
 		}
 
 		processOptions(options);

test/binCases/help/help-output-no-command/stdin.js

@@ -0,0 +1,16 @@
+"use strict";
+
+module.exports = function testAssertions(code, stdout, stderr) {
+	expect(code).toBe(2);
+	expect(stdout).toEqual(expect.anything());
+	expect(stdout).toContain("Config options:");
+	expect(stdout).toContain("Basic options:");
+	expect(stdout).toContain("Module options:");
+	expect(stdout).toContain("Output options:");
+	expect(stdout).toContain("Advanced options:");
+	expect(stdout).toContain("Resolving options:");
+	expect(stdout).toContain("Optimizing options:");
+	expect(stdout).toContain("Stats options:");
+	expect(stdout).toContain("Options:");
+	expect(stderr).toHaveLength(0);
+};