Simplify check_for_changes function

Author: liwagu

src/bootstrap/src/core/build_steps/tool.rs

@@ -583,8 +583,8 @@ impl Step for Rustdoc {
             .unwrap();
 
             let dirs = vec![PathBuf::from("src/librustdoc"), PathBuf::from("src/tools/rustdoc")];
-
-            if let Some(false) = builder.config.check_for_changes(&dirs, &commit, "rustdoc", true) {
+            let has_changes = builder.config.check_for_changes(&dirs, &commit);
+            if !has_changes {
                 let precompiled_rustdoc = builder
                     .config
                     .ci_rustc_dir()

src/bootstrap/src/core/config/config.rs

@@ -2726,17 +2726,25 @@ impl Config {
         }
 
         let dirs = vec![PathBuf::from("compiler"), PathBuf::from("library")];
-        match self.check_for_changes(&dirs, &commit, "download-rustc", if_unchanged) {
-            Some(true) => {
-                println!(
-                    "WARNING: `download-rustc` is enabled, but there are changes to \
-                compiler/ or library/"
-                );
-                Some(commit.to_string())
+        let has_changes = self.check_for_changes(&dirs, &commit);
+
+        if has_changes {
+            if if_unchanged {
+                if self.is_verbose() {
+                    println!(
+                        "WARNING: saw changes to compiler/ or library/ since {commit}; \
+                            ignoring `download-rustc`"
+                    );
+                }
+                return None;
             }
-            Some(false) => Some(commit.to_string()),
-            None => None,
+            println!(
+                "WARNING: `download-rustc` is enabled, but there are changes to \
+                    compiler/ or library/"
+            );
         }
+
+        Some(commit.to_string())
     }
 
     fn parse_download_ci_llvm(
@@ -2836,42 +2844,17 @@ impl Config {
     }
 
     /// Check for changes in specified directories since a given commit.
-    /// Returns Some(true) if changes exist, Some(false) if no changes, None if check should be ignored.
-    pub fn check_for_changes(
-        &self,
-        dirs: &[PathBuf],
-        commit: &str,
-        option_name: &str,
-        if_unchanged: bool,
-    ) -> Option<bool> {
+    /// Returns true if changes exist, false if no changes
+    pub fn check_for_changes(&self, dirs: &[PathBuf], commit: &str) -> bool {
         let mut git = helpers::git(Some(&self.src));
         git.args(["diff-index", "--quiet", commit]);
-
         if !dirs.is_empty() {
             git.arg("--");
             for dir in dirs {
                 git.arg(self.src.join(dir));
             }
         }
-
-        let has_changes = !t!(git.as_command_mut().status()).success();
-
-        if has_changes {
-            if if_unchanged {
-                if self.is_verbose() {
-                    println!(
-                        "WARNING: saw changes to one of {:?} since {}; \
-                        ignoring `{}`",
-                        dirs, commit, option_name
-                    );
-                }
-                None
-            } else {
-                Some(true)
-            }
-        } else {
-            Some(false)
-        }
+        !t!(git.as_command_mut().status()).success()
     }
 }