Upgrade from 4.x to 5.x

Servers to Hosts
- Refactor server($name, $hostname) to host($hostname)
- Refactor localServer($name) to localhost()
- Rename serverList($file) to inventory($file)
Configuration options
- Rename {{server.name}} to {{hostname}}
DotArray syntax

In v5 access to nested arrays in config via dot notation was removed. If you was using it, consider to move to plain config options.

Refactor this:
```
set('a', ['b' => 1]);

// ...

get('a.b');
```
To:
```
set('a_b', 1);

// ...

get('a_b');
```

Upgrade from 3.x to 4.x

Namespace for functions

Add to beginning of deploy.php next line:
```
use function Deployer\{server, task, run, set, get, add, before, after};
```
If you are using PHP version less than 5.6, you can use this:
```
namespace Deployer;
```
env() to set()/get()

Rename all calls env($name, $value) to set($name, $value).

Rename all rvalue env($name) to get($name).

Rename all server(...)->env(...) to server(...)->set(...).
Moved NonFatalException

Rename Deployer\Task\NonFatalException to Deployer\Exception\NonFatalException.
Prior release cleanup

Due to changes in release management, the new cleanup task will ignore any prior releases deployed with 3.x. These will need to be manually removed after migrating to and successfully releasing via 4.x.

Replace your server paths configuration:

server(...)
  ->path(...);

to:

server(...)
  ->env('deploy_path', '...');