feat: add fetch_head configuration option into brew (#679)

src/config.rs

@@ -254,6 +254,7 @@ pub struct Flatpak {
 pub struct Brew {
     greedy_cask: Option<bool>,
     autoremove: Option<bool>,
+    fetch_head: Option<bool>,
 }
 
 #[derive(Debug, Deserialize, Clone, Copy)]
@@ -1096,6 +1097,15 @@ impl Config {
             .unwrap_or(false)
     }
 
+    /// Whether Brew should upgrade formulae built from the HEAD branch
+    pub fn brew_fetch_head(&self) -> bool {
+        self.config_file
+            .brew
+            .as_ref()
+            .and_then(|c| c.fetch_head)
+            .unwrap_or(false)
+    }
+
     /// Whether Composer should update itself
     pub fn composer_self_update(&self) -> bool {
         self.config_file

src/steps/os/unix.rs

@@ -285,10 +285,15 @@ pub fn run_brew_formula(ctx: &ExecutionContext, variant: BrewVariant) -> Result<
     let run_type = ctx.run_type();
 
     variant.execute(run_type).arg("update").status_checked()?;
-    variant
-        .execute(run_type)
-        .args(["upgrade", "--formula"])
-        .status_checked()?;
+
+    let mut command = variant.execute(run_type);
+    command.args(["upgrade", "--formula"]);
+
+    if ctx.config().brew_fetch_head() {
+        command.arg("--fetch-HEAD");
+    }
+
+    command.status_checked()?;
 
     if ctx.config().cleanup() {
         variant.execute(run_type).arg("cleanup").status_checked()?;