feat(username): add detect_env_vars as option (#5833)

* Added the option "detect_env_vars" to the `username` module

with the same functionality as in the `hostname` module.

* Fixed logic error and added test to catch it

* build(deps): update dependency vitepress to ^1.0.0-rc.45

* build(deps): update rust crate shadow-rs to 0.27.1

* Added the option "detect_env_vars" to the `username` module

with the same functionality as in the `hostname` module.

* Fixed logic error and added test to catch it

* Removed unused gix import

* Removed unused gix import, again

* Removed unused gix import. Next try

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

docs/config/README.md

@@ -4357,6 +4357,7 @@ The module will be shown if any of the following conditions are met:
 - The current user isn't the same as the one that is logged in
 - The user is currently connected as an SSH session
 - The variable `show_always` is set to true
+- The array `detect_env_vars` contains at least the name of one environment variable, that is set
 
 ::: tip
 
@@ -4368,13 +4369,14 @@ these variables, one workaround is to set one of them with a dummy value.
 
 ### Options
 
-| Option        | Default                 | Description                                 |
-| ------------- | ----------------------- | ------------------------------------------- |
-| `style_root`  | `'bold red'`            | The style used when the user is root/admin. |
-| `style_user`  | `'bold yellow'`         | The style used for non-root users.          |
-| `format`      | `'[$user]($style) in '` | The format for the module.                  |
-| `show_always` | `false`                 | Always shows the `username` module.         |
-| `disabled`    | `false`                 | Disables the `username` module.             |
+| Option            | Default                 | Description                                               |
+| ----------------- | ----------------------- | --------------------------------------------------------- |
+| `style_root`      | `'bold red'`            | The style used when the user is root/admin.               |
+| `style_user`      | `'bold yellow'`         | The style used for non-root users.                        |
+| `detect_env_vars` | `[]`                    | Which environment variable(s) should trigger this module. |
+| `format`          | `'[$user]($style) in '` | The format for the module.                                |
+| `show_always`     | `false`                 | Always shows the `username` module.                       |
+| `disabled`        | `false`                 | Disables the `username` module.                           |
 
 ### Variables
 
@@ -4385,6 +4387,8 @@ these variables, one workaround is to set one of them with a dummy value.
 
 ### Example
 
+#### Always show the hostname
+
 ```toml
 # ~/.config/starship.toml
 
@@ -4396,6 +4400,17 @@ disabled = false
 show_always = true
 ```
 
+#### Hide the hostname in remote tmux sessions
+
+```toml
+# ~/.config/starship.toml
+
+[hostname]
+ssh_only = false
+detect_env_vars = ['!TMUX', 'SSH_CONNECTION']
+disabled = false
+```
+
 ## Vagrant
 
 The `vagrant` module shows the currently installed version of [Vagrant](https://www.vagrantup.com/).