Update snaps (fixes #29)

README.md

@@ -37,6 +37,8 @@ Just run `topgrade`. It will run the following steps:
   * [Plug](https://github.com/junegunn/vim-plug)
 * Upgrade NPM globally installed packages
 * Upgrade Atom packages
+* *Linux*: Update Flatpak packages
+* *Linux*: Update snap packages
 * *Linux*: Run [fwupdmgr](https://github.com/hughsie/fwupd) to show firmware upgrade. (View
   only. No upgrades will actually be performed)
 * Run custom defined commands

src/main.rs

@@ -171,11 +171,6 @@ fn run() -> Result<(), Error> {
         run_rustup(&rustup).report("rustup", &mut reports);
     }
 
-    if let Ok(flatpak) = which("flatpak") {
-        terminal.print_separator("Flatpak");
-        run_flatpak(&flatpak).report("Flatpak", &mut reports);
-    }
-
     let cargo_upgrade = home_path(".cargo/bin/cargo-install-update");
     if cargo_upgrade.exists() {
         terminal.print_separator("Cargo");
@@ -214,6 +209,20 @@ fn run() -> Result<(), Error> {
         run_apm(&apm).report("Atom Package Manager", &mut reports);
     }
 
+    if cfg!(target_os = "linux") {
+        if let Ok(flatpak) = which("flatpak") {
+            terminal.print_separator("Flatpak");
+            run_flatpak(&flatpak).report("Flatpak", &mut reports);
+        }
+
+        if let Some(sudo) = &sudo {
+            if let Ok(snap) = which("snap") {
+                terminal.print_separator("snap");
+                run_snap(&sudo, &snap).report("snap", &mut reports);
+            }
+        }
+    }
+
     if let Some(commands) = config.commands() {
         for (name, command) in commands {
             terminal.print_separator(name);

src/steps.rs

@@ -162,3 +162,13 @@ pub fn run_flatpak(flatpak: &PathBuf) -> Result<(), failure::Error> {
 
     Ok(())
 }
+
+pub fn run_snap(sudo: &PathBuf, snap: &PathBuf) -> Result<(), failure::Error> {
+    Command::new(&sudo)
+        .args(&[snap.to_str().unwrap(), "refresh"])
+        .spawn()?
+        .wait()?
+        .check()?;
+
+    Ok(())
+}