Add --2.2 flag, update installer docs, update installer checksum

Fixes composer/composer#10682

templates/download.html.twig

@@ -25,7 +25,7 @@
         To automate the installation, use <a href="/doc/faqs/how-to-install-composer-programmatically.md" title="See the instructions on how to install Composer programmatically" aria-label="See the instructions on how to install Composer programmatically">the guide on installing Composer programmatically</a>.
     </p>
     <pre class="installer">php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
-php -r "if (hash_file('sha384', 'composer-setup.php') === '906a84df04cea2aa72f40b5f787e49f22d4c2f19492ac310e8cba5b96ac8b64115ac402c8cd292b8a03482574915d1a8') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
+php -r "if (hash_file('sha384', 'composer-setup.php') === '55ce33d7678c5a611085589f1f3ddf8b3c52d662cd01d4ba75c0ee0459970c2200a51f492d557530c71c15d8dba01eae') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
 php composer-setup.php
 php -r "unlink('composer-setup.php');"</pre>
 
@@ -71,6 +71,10 @@ php -r "unlink('composer-setup.php');"</pre>
         target release. Example:</p>
     <code>php composer-setup.php --version=1.0.0-alpha8</code>
 
+    <h3>--preview, --snapshot, --1 (EOL), --2, --2.2 (LTS)</h3>
+    <p>Select a specific version channel instead of the default latest stable. See "Download channels" below for more details. Example:</p>
+    <code>php composer-setup.php --2.2</code>
+
     <h3>--help</h3>
     <p>The installer provides more options for specific environments, use the
         <code>--help</code> option to see all of them.</p>
@@ -84,8 +88,8 @@ php -r "unlink('composer-setup.php');"</pre>
         For snapshot builds, which are done from the latest Composer commit,
         you can use the <code>--snapshot</code> flag.<br>
         To programmatically install specific major versions you can use the
-        <code>--1</code> or <code>--2</code> flag. Example:</p>
-    <code>php composer-setup.php --preview</code>
+        <code>--1</code> or <code>--2</code> flag. To select the latest 2.2 LTS
+        you can use <code>--2.2</code>.</p>
 
     <h2>Manual Download</h2>
     <p>If you prefer to download the phar manually, here are the available versions:</p>

web/installer

@@ -50,8 +50,7 @@ function process($argv)
     // Determine ANSI output from --ansi and --no-ansi flags
     setUseAnsi($argv);
 
-    $help = in_array('--help', $argv);
-    $help = $help || in_array('-h', $argv);
+    $help = in_array('--help', $argv) || in_array('-h', $argv);
     if ($help) {
         displayHelp();
         exit(0);
@@ -69,6 +68,8 @@ function process($argv)
         $channel = '1';
     } elseif (in_array('--2', $argv)) {
         $channel = '2';
+    } elseif (in_array('--2.2', $argv)) {
+        $channel = '2.2';
     }
     $disableTls = in_array('--disable-tls', $argv);
     $installDir = getOptValue('--install-dir', $argv, false);
@@ -92,6 +93,10 @@ function process($argv)
     }
 
     if ($ok || $force) {
+        if ($channel === '1' && !$quiet) {
+            out('Warning: You forced the install of Composer 1.x via --1, but Composer 2.x is the latest stable version. Updating to it via composer self-update --stable is recommended.', 'error');
+        }
+
         $installer = new Installer($quiet, $disableTls, $cafile);
         if ($installer->run($version, $installDir, $filename, $channel)) {
             showWarnings($warnings);
@@ -121,8 +126,9 @@ Options
 --install-dir="..."  accepts a target installation directory
 --preview            install the latest version from the preview (alpha/beta/rc) channel instead of stable
 --snapshot           install the latest version from the snapshot (dev builds) channel instead of stable
---1                  install the latest stable Composer 1.x version
+--1                  install the latest stable Composer 1.x (EOL) version
 --2                  install the latest stable Composer 2.x version
+--2.2                install the latest stable Composer 2.2.x (LTS) version
 --version="..."      accepts a specific version to install instead of the latest
 --filename="..."     accepts a target filename (default: composer.phar)
 --disable-tls        disable SSL/TLS security for file downloads
@@ -702,7 +708,7 @@ class Installer
             $result = $this->install($version, $channel);
 
             // in case --1 or --2 is passed, we leave the default channel for next self-update to stable
-            if (is_numeric($channel)) {
+            if (1 === preg_match('{^\d+$}D', $channel)) {
                 $channel = 'stable';
             }