radicle: ensure stable commits for Docs

`Doc::commit` used `git2::Signature::now` when committing the document
to the repository. This results in the commits always changing and not
allowing us to test outputs of our CLI commands that would wish to
output the SHA.

Make `Doc::commit` reproducible in debug mode using `debug_assertions`
and checking the `RAD_COMMIT_TIME` environment variable.

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett

radicle/src/identity/doc.rs

@@ -276,6 +276,17 @@ impl Doc<Verified> {
             .signature()
             .or_else(|_| git2::Signature::now("radicle", remote.to_string().as_str()))?;
 
+        #[cfg(debug_assertions)]
+        let sig = if let Ok(s) = std::env::var("RAD_COMMIT_TIME") {
+            // SAFETY: Only used in test code.
+            #[allow(clippy::unwrap_used)]
+            let timestamp = s.trim().parse::<i64>().unwrap();
+            let time = git2::Time::new(timestamp, 0);
+            git2::Signature::new("radicle", remote.to_string().as_str(), &time)?
+        } else {
+            sig
+        };
+
         let mut msg = format!("{}\n\n", msg.trim());
         for (key, sig) in signatures {
             writeln!(&mut msg, "{}: {key} {sig}", trailers::SIGNATURE_TRAILER)