Detect if Takeout is running in a container and use host.docker.localhost instead of localhost

This works on Windows and Mac, but will require Linux users to add
`--add-host=docker.internal.host:host-gateway` to their aliases. The
docs was updated.

Author: tonysm

README.md

@@ -32,19 +32,19 @@ The recommended way to install Takeout is the dockerized version via an alias (a
 On Linux or macOS, use:
 
 ```bash
-alias takeout="docker run --rm -v /var/run/docker.sock:/var/run/docker.sock -it tighten/takeout:latest"
+alias takeout="docker run --rm -v /var/run/docker.sock:/var/run/docker.sock --add-host=host.docker.internal:host-gateway -it tighten/takeout:latest"
 ```
 
-On Windows 10, if you're using Bash, use:
+On Windows 10|11, if you're using Bash, use:
 
 ```bash
-alias takeout="docker run --rm -v //var/run/docker.sock:/var/run/docker.sock -it tighten/takeout:latest"
+alias takeout="docker run --rm -v //var/run/docker.sock:/var/run/docker.sock --add-host=host.docker.internal:host-gateway -it tighten/takeout:latest"
 ```
 
-On Windows 10, if you're using PowerShell, use:
+On Windows 10|11, if you're using PowerShell, use:
 
 ```bash
-function takeout { docker run --rm -v //var/run/docker.sock:/var/run/docker.sock -it tighten/takeout:latest $args }
+function takeout { docker run --rm -v //var/run/docker.sock:/var/run/docker.sock --add-host=host.docker.internal:host-gateway -it tighten/takeout:latest $args }
 ```
 
 That's it. You may now use Takeout on your terminal. The first time you use this alias, it will pull the Takeout image from Docker Hub.

app/Shell/Environment.php

@@ -32,7 +32,7 @@ public function portIsAvailable($port): bool
         // If we cannot open the socket, it means there's nothing running on it, so the
         // port is available. If we are successful, that means it is already in use.
 
-        $socket = @fsockopen('localhost', $port, $errorCode, $errorMessage, timeout: 5);
+        $socket = @fsockopen($this->localhost(), $port, $errorCode, $errorMessage, timeout: 5);
 
         if (! $socket) {
             return true;
@@ -43,6 +43,11 @@ public function portIsAvailable($port): bool
         return false;
     }
 
+    public function isTakeoutRunningOnDocker(): bool
+    {
+        return boolval($_SERVER['TAKEOUT_CONTAINER'] ?? false);
+    }
+
     public function userIsInDockerGroup(): bool
     {
         return $this->shell->execQuietly('groups | grep docker')->isSuccessful();
@@ -63,4 +68,9 @@ public function homeDirectory(): string
 
         return '~';
     }
+
+    private function localhost(): string
+    {
+        return $this->isTakeoutRunningOnDocker() ? 'host.docker.internal' : 'localhost';
+    }
 }