Support Void (fix #95)

README.md

@@ -36,6 +36,7 @@ Just run `topgrade`. It will run the following steps:
   * *Debian/Ubuntu*: Run `apt update && apt dist-upgrade`
   * *Gentoo*: Run `layman -s ALL && emerge --sync -q && eix-update && emerge -uDNa world`
   * *openSUSE*: Run `zypper refresh && zypper dist-upgrade`
+  * *Void*: Run `xbps-install -Su`
 * *Linux*: Run [etc-update](https://dev.gentoo.org/~zmedico/portage/doc/man/etc-update.1.html):
 * *FreeBSD*: Upgrade and audit packages
 * *Unix*: Run `brew update && brew upgrade`. This should handle both Homebrew and Linuxbrew

src/linux.rs

@@ -16,6 +16,7 @@ pub enum Distribution {
     Ubuntu,
     Gentoo,
     OpenSuse,
+    Void,
 }
 
 #[derive(Debug, Fail)]
@@ -54,6 +55,10 @@ impl Distribution {
             return Ok(Distribution::OpenSuse);
         }
 
+        if content.contains("void") {
+            return Ok(Distribution::Void);
+        }
+
         if PathBuf::from("/etc/gentoo-release").exists() {
             return Ok(Distribution::Gentoo);
         }
@@ -77,6 +82,7 @@ impl Distribution {
             Distribution::Ubuntu | Distribution::Debian => upgrade_debian(&sudo, terminal, dry_run),
             Distribution::Gentoo => upgrade_gentoo(&sudo, terminal, dry_run),
             Distribution::OpenSuse => upgrade_opensuse(&sudo, terminal, dry_run),
+            Distribution::Void => upgrade_void(&sudo, terminal, dry_run),
         };
 
         Some(("System update", success.is_ok()))
@@ -170,6 +176,20 @@ fn upgrade_opensuse(sudo: &Option<PathBuf>, terminal: &mut Terminal, dry_run: bo
     Ok(())
 }
 
+fn upgrade_void(sudo: &Option<PathBuf>, terminal: &mut Terminal, dry_run: bool) -> Result<(), failure::Error> {
+    if let Some(sudo) = &sudo {
+        Executor::new(&sudo, dry_run)
+            .args(&["/usr/bin/xbps-install", "-Su"])
+            .spawn()?
+            .wait()?
+            .check()?;
+    } else {
+        terminal.print_warning("No sudo detected. Skipping system upgrade");
+    }
+
+    Ok(())
+}
+
 fn upgrade_fedora(sudo: &Option<PathBuf>, terminal: &mut Terminal, dry_run: bool) -> Result<(), failure::Error> {
     if let Some(sudo) = &sudo {
         Executor::new(&sudo, dry_run)