Only have commit hash in version if git doesn't error (#2336)

* Add commit to version command

* Replace unwrap with expect.

* Only have commit hash if git doesn't error

Co-authored-by: Jonathan Turner <jonathandturner@users.noreply.github.com>

crates/nu-cli/Cargo.toml

@@ -114,6 +114,8 @@ optional = true
 version = "0.23.1"
 
 [build-dependencies]
+git2 = "0.13"
+
 
 [dev-dependencies]
 quickcheck = "0.9"

crates/nu-cli/build.rs

@@ -0,0 +1,28 @@
+use git2::Repository;
+use std::path::Path;
+use std::{env, fs, io};
+
+fn main() -> Result<(), io::Error> {
+    let out_dir = env::var_os("OUT_DIR").expect(
+    "\
+        OUT_DIR environment variable not found. \
+        OUT_DIR is guaranteed to to exist in a build script by cargo - see \
+        https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts\
+    ");
+
+    let latest_commit_hash = latest_commit_hash(env::current_dir()?).unwrap_or_default();
+
+    let commit_hash_path = Path::new(&out_dir).join("git_commit_hash");
+    fs::write(commit_hash_path, latest_commit_hash)?;
+
+    Ok(())
+}
+
+fn latest_commit_hash<P: AsRef<Path>>(dir: P) -> Result<String, git2::Error> {
+    let dir = dir.as_ref();
+    Ok(Repository::discover(dir)?
+        .head()?
+        .peel_to_commit()?
+        .id()
+        .to_string())
+}

crates/nu-cli/src/commands/version.rs

@@ -5,6 +5,8 @@ use indexmap::IndexMap;
 use nu_errors::ShellError;
 use nu_protocol::{Dictionary, Signature, UntaggedValue};
 
+const GIT_COMMIT_HASH: &str = include_str!(concat!(env!("OUT_DIR"), "/git_commit_hash"));
+
 pub struct Version;
 
 #[async_trait]
@@ -48,6 +50,14 @@ pub fn version(args: CommandArgs, _registry: &CommandRegistry) -> Result<OutputS
         UntaggedValue::string(clap::crate_version!()).into_value(&tag),
     );
 
+    let commit_hash = Some(GIT_COMMIT_HASH.trim()).filter(|x| x.is_empty());
+    if let Some(commit_hash) = commit_hash {
+        indexmap.insert(
+            "commit_hash".to_string(),
+            UntaggedValue::string(commit_hash).into_value(&tag),
+        );
+    }
+
     indexmap.insert("features".to_string(), features_enabled(&tag).into_value());
 
     let value = UntaggedValue::Row(Dictionary::from(indexmap)).into_value(&tag);