Add ability to disable package managers (fix #206)

src/config.rs

@@ -24,6 +24,8 @@ type Commands = BTreeMap<String, String>;
 pub enum Step {
     /// Don't perform system upgrade
     System,
+    /// Don't perform upgrades of package managers
+    PackageManagers,
     /// Don't pull git repositories
     GitRepos,
     /// Don't upgrade Vim packages or configuration files

src/main.rs

@@ -176,6 +176,8 @@ fn run() -> Result<(), Error> {
     }
 
     #[cfg(windows)]
+    {
+        if config.should_run(Step::PackageManagers) {
             execute(
                 &mut report,
                 "Chocolatey",
@@ -183,32 +185,47 @@ fn run() -> Result<(), Error> {
                 config.no_retry(),
             )?;
 
-    #[cfg(windows)]
             execute(&mut report, "Scoop", || windows::run_scoop(run_type), config.no_retry())?;
+        }
+    }
 
     #[cfg(unix)]
+    {
+        if config.should_run(Step::PackageManagers) {
             execute(
                 &mut report,
                 "brew",
                 || unix::run_homebrew(config.cleanup(), run_type),
                 config.no_retry(),
             )?;
+        }
+
+        execute(&mut report, "nix", || unix::run_nix(run_type), config.no_retry())?;
+    }
+
     #[cfg(target_os = "dragonfly")]
+    {
+        if config.should_run(Step::PackageManagers) {
             execute(
                 &mut report,
                 "DragonFly BSD Packages",
                 || dragonfly::upgrade_packages(sudo.as_ref(), run_type),
                 config.no_retry(),
             )?;
+        }
+    }
+
     #[cfg(target_os = "freebsd")]
+    {
+        if config.should_run(Step::PackageManagers) {
             execute(
                 &mut report,
                 "FreeBSD Packages",
                 || freebsd::upgrade_packages(sudo.as_ref(), run_type),
                 config.no_retry(),
             )?;
-    #[cfg(unix)]
+        }
-    execute(&mut report, "nix", || unix::run_nix(run_type), config.no_retry())?;
+    }
 
     let emacs = emacs::Emacs::new(&base_dirs);
     if config.should_run(Step::Emacs) {
@@ -405,7 +422,7 @@ fn run() -> Result<(), Error> {
 
     #[cfg(target_os = "linux")]
     {
-        if config.should_run(Step::System) {
+        if config.should_run(Step::PackageManagers) {
             execute(
                 &mut report,
                 "Flatpak",
@@ -551,7 +568,7 @@ fn run() -> Result<(), Error> {
     if report.data().iter().all(|(_, succeeded)| *succeeded) {
         Ok(())
     } else {
-        Err(ErrorKind::StepFailed)?
+        Err(ErrorKind::StepFailed.into())
     }
 }