feat: add hostname module (#286)

Add a hostname module as requested by @chipbuster.
Displays the system hostname as provided by gethostname.

src/modules/hostname.rs

@@ -0,0 +1,39 @@
+use ansi_term::{Color, Style};
+use std::env;
+use std::process::Command;
+
+use super::{Context, Module};
+use std::ffi::OsString;
+
+/// Creates a module with the system hostname
+///
+/// Will display the hostname if all of the following criteria are met:
+///     - hostname.disabled is absent or false
+///     - hostname.ssh_only is false OR the user is currently connected as an SSH session (`$SSH_CONNECTION`)
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let mut module = context.new_module("hostname")?;
+
+    let ssh_connection = env::var("SSH_CONNECTION").ok();
+    if module.config_value_bool("ssh_only").unwrap_or(true) && ssh_connection.is_none() {
+        return None;
+    }
+
+    let os_hostname: OsString = gethostname::gethostname();
+
+    let host = match os_hostname.into_string() {
+        Ok(host) => host,
+        Err(bad) => {
+            log::debug!("hostname is not valid UTF!\n{:?}", bad);
+            return None;
+        }
+    };
+
+    let prefix = module.config_value_str("prefix").unwrap_or("").to_owned();
+    let suffix = module.config_value_str("suffix").unwrap_or("").to_owned();
+
+    module.set_style(Color::Green.bold().dimmed());
+    module.new_segment("hostname", &format!("{}{}{}", prefix, host, suffix));
+    module.get_prefix().set_value("on ");
+
+    Some(module)
+}

src/modules/mod.rs

@@ -5,6 +5,7 @@ mod directory;
 mod git_branch;
 mod git_status;
 mod golang;
+mod hostname;
 mod jobs;
 mod line_break;
 mod nix_shell;
@@ -40,6 +41,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
         "cmd_duration" => cmd_duration::module(context),
         "jobs" => jobs::module(context),
         "nix_shell" => nix_shell::module(context),
+        "hostname" => hostname::module(context),
 
         _ => {
             eprintln!("Error: Unknown module {}. Use starship module --list to list out all supported modules.", module);

src/print.rs

@@ -13,6 +13,7 @@ use crate::modules;
 // prompt heading of config docs needs to be updated according to changes made here.
 const DEFAULT_PROMPT_ORDER: &[&str] = &[
     "username",
+    "hostname",
     "directory",
     "git_branch",
     "git_status",