Self rename in Windows (fix #458) (#460)

src/self_renamer.rs

@@ -0,0 +1,43 @@
+#![cfg(windows)]
+
+use anyhow::Result;
+use log::{debug, error};
+use std::{env::current_exe, fs, path::PathBuf};
+
+pub struct SelfRenamer {
+    exe_path: PathBuf,
+    temp_path: PathBuf,
+}
+
+impl SelfRenamer {
+    pub fn create() -> Result<Self> {
+        let tempdir = tempfile::tempdir()?;
+        let temp_path = tempdir.path().join("topgrade.exe");
+        let exe_path = current_exe()?;
+
+        debug!("Current exe in {:?}. Moving it to {:?}", exe_path, temp_path);
+
+        fs::rename(&exe_path, &temp_path)?;
+
+        Ok(SelfRenamer { exe_path, temp_path })
+    }
+}
+
+impl Drop for SelfRenamer {
+    fn drop(&mut self) {
+        if self.exe_path.exists() {
+            debug!("{:?} exists. Topgrade was probably upgraded", self.exe_path);
+            return;
+        }
+
+        match fs::rename(&self.temp_path, &self.exe_path) {
+            Ok(_) => debug!("Moved topgrade back from {:?} to {:?}", self.temp_path, self.exe_path),
+            Err(e) => error!(
+                "Could not move Topgrade from {} back to {}: {}",
+                self.temp_path.display(),
+                self.exe_path.display(),
+                e
+            ),
+        }
+    }
+}