Add git commit info and date to generated crates.

Author: cr1901

src/generate/device.rs

@@ -20,13 +20,29 @@ pub fn render(
 ) -> Result<TokenStream> {
     let mut out = TokenStream::new();
 
+    let commit_info = {
+        let tmp = include_str!(concat!(env!("OUT_DIR"), "/commit-info.txt"));
+
+        if tmp.is_empty() {
+            " (unknown commit)"
+        } else {
+            tmp
+        }
+    };
+
     let doc = format!(
         "Peripheral access API for {0} microcontrollers \
-         (generated using svd2rust v{1})\n\n\
-         You can find an overview of the API [here].\n\n\
-         [here]: https://docs.rs/svd2rust/{1}/svd2rust/#peripheral-api",
+         (generated using svd2rust v{1}{2})\n\n\
+         You can find an overview of the API as of release v{1} [here].\n\n\
+         Docs containing API features to be included in the [next] \
+         release can be generated by cloning the svd2rust [repository], \
+         checking out the above commit, and running `cargo doc`.\n\n\
+         [here]: https://docs.rs/svd2rust/{1}/svd2rust/#peripheral-api\n\
+         [next]: https://github.com/rust-embedded/svd2rust/blob/master/CHANGELOG.md#unreleased\n\
+         [repository]: https://github.com/rust-embedded/svd2rust",
         d.name.to_uppercase(),
-        env!("CARGO_PKG_VERSION")
+        env!("CARGO_PKG_VERSION"),
+        commit_info
     );
 
     if target == Target::Msp430 {