Move step running into enum for dynamic ordering (#1188)

Co-authored-by: Stuart Reilly <sreilly@scottlogic.com>

src/execution_context.rs

@@ -1,5 +1,7 @@
 #![allow(dead_code)]
 use crate::executor::RunType;
+#[cfg(target_os = "linux")]
+use crate::steps::linux::Distribution;
 use crate::sudo::Sudo;
 use crate::utils::{get_require_sudo_string, require_option};
 use crate::{config::Config, executor::Executor};
@@ -18,10 +20,17 @@ pub struct ExecutionContext<'a> {
     tmux_session: Mutex<Option<String>>,
     /// True if topgrade is running under ssh.
     under_ssh: bool,
+    #[cfg(target_os = "linux")]
+    distribution: &'a Result<Distribution>,
 }
 
 impl<'a> ExecutionContext<'a> {
-    pub fn new(run_type: RunType, sudo: Option<Sudo>, config: &'a Config) -> Self {
+    pub fn new(
+        run_type: RunType,
+        sudo: Option<Sudo>,
+        config: &'a Config,
+        #[cfg(target_os = "linux")] distribution: &'a Result<Distribution>,
+    ) -> Self {
         let under_ssh = var("SSH_CLIENT").is_ok() || var("SSH_TTY").is_ok();
         Self {
             run_type,
@@ -29,6 +38,8 @@ impl<'a> ExecutionContext<'a> {
             config,
             tmux_session: Mutex::new(None),
             under_ssh,
+            #[cfg(target_os = "linux")]
+            distribution,
         }
     }
 
@@ -60,4 +71,9 @@ impl<'a> ExecutionContext<'a> {
     pub fn get_tmux_session(&self) -> Option<String> {
         self.tmux_session.lock().unwrap().clone()
     }
+
+    #[cfg(target_os = "linux")]
+    pub fn distribution(&self) -> &Result<Distribution> {
+        self.distribution
+    }
 }