Exclude target directory from Time Machine

Cargo.toml

@@ -54,6 +54,9 @@ url = "1.1"
 [target.'cfg(unix)'.dependencies]
 openssl = "0.9"
 
+[target.'cfg(target_os = "macos")'.dependencies]
+core-foundation = { version = "0.4.4", features = ["mac_os_10_7_support"] }
+
 [target.'cfg(windows)'.dependencies]
 advapi32-sys = "0.2"
 kernel32-sys = "0.2"

src/cargo/lib.rs

@@ -34,6 +34,8 @@ extern crate tempdir;
 extern crate termcolor;
 extern crate toml;
 extern crate url;
+#[cfg(target_os = "macos")]
+extern crate core_foundation;
 
 use std::fmt;
 use std::error::Error;

src/cargo/ops/cargo_rustc/layout.rs

@@ -108,11 +108,42 @@ impl Layout {
         })
     }
 
+    #[cfg(not(target_os = "macos"))]
+    fn exclude_from_backups(&self, _: &Path) {}
+
+    #[cfg(target_os = "macos")]
+    /// Marks files or directories as excluded from Time Machine on macOS
+    ///
+    /// This is recommended to prevent derived/temporary files from bloating backups.
+    fn exclude_from_backups(&self, path: &Path) {
+        use std::ptr;
+        use core_foundation::{url, number, string};
+        use core_foundation::base::TCFType;
+
+        // For compatibility with 10.7 a string is used instead of global kCFURLIsExcludedFromBackupKey
+        let is_excluded_key: Result<string::CFString, _> = "NSURLIsExcludedFromBackupKey".parse();
+        match (url::CFURL::from_path(path, false), is_excluded_key) {
+            (Some(path), Ok(is_excluded_key)) => unsafe {
+                url::CFURLSetResourcePropertyForKey(
+                    path.as_concrete_TypeRef(),
+                    is_excluded_key.as_concrete_TypeRef(),
+                    number::kCFBooleanTrue as *const _,
+                    ptr::null_mut(),
+                );
+            },
+            // Errors are ignored, since it's an optional feature and failure
+            // doesn't prevent Cargo from working
+            _ => {}
+        }
+    }
+
     pub fn prepare(&mut self) -> io::Result<()> {
         if fs::metadata(&self.root).is_err() {
             fs::create_dir_all(&self.root)?;
         }
 
+        self.exclude_from_backups(&self.root);
+
         mkdir(&self.deps)?;
         mkdir(&self.native)?;
         mkdir(&self.incremental)?;