Add rerun-if-changed to libgit2-sys build script. (#640)

Author: ehuss

libgit2-sys/build.rs

@@ -182,6 +182,10 @@ fn main() {
         println!("cargo:rustc-link-lib=framework=Security");
         println!("cargo:rustc-link-lib=framework=CoreFoundation");
     }
+
+    rerun_if(Path::new("libgit2/include"));
+    rerun_if(Path::new("libgit2/src"));
+    rerun_if(Path::new("libgit2/deps"));
 }
 
 fn cp_r(from: impl AsRef<Path>, to: impl AsRef<Path>) {
@@ -214,3 +218,13 @@ fn add_c_files(build: &mut cc::Build, path: impl AsRef<Path>) {
         }
     }
 }
+
+fn rerun_if(path: &Path) {
+    if path.is_dir() {
+        for entry in fs::read_dir(path).expect("read_dir") {
+            rerun_if(&entry.expect("entry").path());
+        }
+    } else {
+        println!("cargo:rerun-if-changed={}", path.display());
+    }
+}