feat: allow hljs to be run from command line

This allows the ability for hljs's build script to be run from
the command line.

This is useful for sofware that requires hljs as part of a build
chain.

It disables generation of docs and demo by default.

The patch adds the following options to "tools/build.js":

 * `--output`: path to write build files to. Defaults to "build".
 * `--docs`: tells builder to include the docs and demo.

Build just for Web, don't include docs:

```Bash
hljs --output "some/path xml" javascript
```

Build for Web, include docs:

```Bash
hljs --docs --output "some/path" xml javascript
```

Build for NodeJS:

```Bash
hljs -t node --output "some/path" xml javascript
```

Build for everything:

```Bash
hljs -t all --output "some/path" xml javascript
```

tools/browser.js

@@ -8,10 +8,10 @@ let path     = require('path');
 let registry = require('./tasks');
 let utility  = require('./utility');
 
-let directory;
+let directory = {};
 
 function templateAllFunc(blobs) {
-  const name = path.join('demo', 'index.html');
+  const name = path.join(directory.root, 'demo/index.html');
 
   blobs = _.compact(blobs);
 
@@ -69,29 +69,29 @@ function generateDemo(filterCB, readArgs) {
     writeImages: { requires:'readImages', task: ['dest', destArgs] },
     readDemoJS: {
       requires: 'logStart',
-      task: ['read', path.join('demo', 'demo.js')]
+      task: ['read', path.join(directory.root, 'demo/demo.js')]
     },
     minifyDemoJS: { requires: 'readDemoJS', task: 'jsminify' },
     writeDemoJS: { requires: 'minifyDemoJS', task: ['dest', demoRoot] },
     readDemoCSS: {
       requires: 'logStart',
-      task: ['read', path.join('demo', 'style.css')]
+      task: ['read', path.join(directory.root, 'demo/style.css')]
     },
     minifyDemoCSS: { requires: 'readDemoCSS', task: 'cssminify' },
     writeDemoCSS: { requires: 'minifyDemoCSS', task: ['dest', demoRoot] }
   };
 }
 
 module.exports = function(commander, dir) {
-  directory = dir;
+  Object.assign(directory, dir);
 
   let hljsExt, output, requiresTask, tasks,
       replace           = utility.replace,
       regex             = utility.regex,
       replaceClassNames = utility.replaceClassNames,
 
-      coreFile     = path.join('src', 'highlight.js'),
-      languages    = utility.glob(path.join('src', 'languages', '*.js')),
+      coreFile     = path.join(directory.root, 'src/highlight.js'),
+      languages    = utility.glob(path.join(directory.root, 'src/languages', '*.js')),
       filterCB     = utility.buildFilterCallback(commander.args),
       replaceArgs  = replace(regex.header, ''),
       templateArgs =
@@ -152,7 +152,7 @@ module.exports = function(commander, dir) {
     task: ['write', output]
   };
 
-  tasks = (commander.target === 'browser')
+  tasks = (commander.target === 'browser' && commander.docs)
         ? [copyDocs(), generateDemo(filterCB, languages), tasks]
         : [tasks];
 

tools/build.js

@@ -1,3 +1,4 @@
+#!/usr/bin/env node
 // For the basic introductions on using this build script, see:
 //
 // <https://highlightjs.readthedocs.org/en/latest/building-testing.html>
@@ -12,9 +13,11 @@
 //
 //   The default target. This will package up the core `highlight.js` along
 //   with all the language definitions into the file `highlight.pack.js` --
-//   which will be compressed without including the option to disable it. It
-//   also builds the documentation for our readthedocs page, mentioned
-//   above, along with a local instance of the demo at:
+//   which will be compressed without including the option to disable it.
+//
+//   If the --docs options is set, it also builds the documentation for our
+//   readthedocs page, mentioned above, along with a local instance of the demo
+//   at:
 //
 //   <https://highlightjs.org/static/demo/>.
 //
@@ -65,25 +68,28 @@ let path      = require('path');
 let Queue     = require('gear').Queue;
 let registry  = require('./tasks');
 
-let build, dir = {};
+const defaultOutPath = path.resolve(__dirname, '../build');
 
 commander
   .usage('[options] [<language>...]')
+  .option('-d, --docs', 'Include documentation and demo (when target "browser")')
   .option('-n, --no-compress', 'Disable compression')
+  .option('-o, --output <path>', 'directory to output to', defaultOutPath)
   .option('-t, --target <name>', 'Build for target ' +
                                  '[all, browser, cdn, node]',
                                  /^(browser|cdn|node|all)$/i, 'browser')
   .parse(process.argv);
 
 commander.target = commander.target.toLowerCase();
 
-build     = require(`./${commander.target}`);
-dir.root  = path.dirname(__dirname);
-dir.build = path.join(dir.root, 'build');
+const build   = require(`./${commander.target}`);
+const dir = {
+  build: path.resolve(process.cwd(), commander.output),
+  root: path.resolve(__dirname, "../"),
+};
 
 new Queue({ registry: registry })
-  .clean(dir.build)
-  .log('Starting build.')
+  .log(`⚒ Starting build for "${commander.target}."`)
   .series(build(commander, dir))
-  .log('Finished build.')
+  .log('❤️ Finished build.')
   .run();

tools/node.js

@@ -82,7 +82,7 @@ function copyMetaFiles() {
       glob   = `{README.md,LICENSE,${docs}}`,
 
       input  = utility.glob(path.join(directory.root, glob)),
-      output = { dir: directory.build, base: '.' };
+      output = { dir: directory.build, base: directory.build };
 
   return {
     startLog: { task: ['log', 'Copying meta files.'] },