fix: set executable bit on brioche binary if not already set (#112)

* fix: set executable bit on brioche binary if not already set

The code changes in `self_update.rs` add logic to set the executable bit on the `brioche` binary if it's not already set. This ensures that the binary can be executed properly after a self update.

Signed-off-by: Jérémy Audiger <jeremy.audiger@icloud.com>

* refactor: apply the file permissions on the temporary file

Signed-off-by: Jérémy Audiger <jeremy.audiger@icloud.com>

---------

Signed-off-by: Jérémy Audiger <jeremy.audiger@icloud.com>

crates/brioche/src/self_update.rs

@@ -1,6 +1,7 @@
 use std::{
     collections::HashMap,
     io::{IsTerminal, Write as _},
+    os::unix::fs::PermissionsExt,
 };
 
 use anyhow::Context as _;
@@ -73,9 +74,30 @@ pub async fn self_update(args: SelfUpdateArgs) -> anyhow::Result<bool> {
 
     println!("Downloaded update");
 
+    // Write the update to a temporary file
     tokio::fs::write(&brioche_path_temp, new_update)
         .await
         .with_context(|| format!("failed to write update to {}", brioche_path_temp.display()))?;
+
+    // Set the executable bit if it's not already set
+    let mut permissions = tokio::fs::metadata(&brioche_path_temp)
+        .await
+        .with_context(|| format!("failed to get metadata for {}", brioche_path_temp.display()))?
+        .permissions();
+    const EXECUTABLE_BIT: u32 = 0o111;
+    if permissions.mode() & EXECUTABLE_BIT != EXECUTABLE_BIT {
+        permissions.set_mode(permissions.mode() | EXECUTABLE_BIT);
+        tokio::fs::set_permissions(&brioche_path_temp, permissions)
+            .await
+            .with_context(|| {
+                format!(
+                    "failed to set executable bit on {}",
+                    brioche_path_temp.display()
+                )
+            })?;
+    }
+
+    // Rename the temporary file to the actual file
     tokio::fs::rename(&brioche_path_temp, &brioche_path)
         .await
         .with_context(|| {