feat: add --latest flag to get the latest job run

src/bin/rad-job.rs

@@ -273,15 +273,23 @@ where
 }
 
 fn show_job<A>(
-    command::Show { pretty, rev }: command::Show,
+    command::Show {
+        pretty,
+        latest,
+        rev,
+    }: command::Show,
     jobs: &Jobs<Repository, A>,
 ) -> Result<(), error::Show>
 where
     A: Access,
 {
-    // Resolve shorthand revisions (e.g. `bf23a86`) to a full commit OID.
-    let oid = revparse(jobs.as_ref(), &rev)?;
-    let (id, job) = find_by_commit(oid, jobs)?;
+    let (id, job) = if latest {
+        latest_job(jobs)?
+    } else {
+        let rev = rev.expect("rev is required unless --latest");
+        let oid = revparse(jobs.as_ref(), &rev)?;
+        find_by_commit(oid, jobs)?
+    };
     let show = radicle_job::display::Job::new(id, &job);
     if pretty {
         println!("{}", show.pretty());
@@ -305,6 +313,21 @@ where
         .map_err(|err| error::Find::FindCommit { oid, err })
 }
 
+/// Find the job with the most recent run activity, across all nodes.
+fn latest_job<A>(jobs: &Jobs<Repository, A>) -> Result<(JobId, Job), error::Latest>
+where
+    A: Access,
+{
+    jobs.all()
+        .map_err(error::Latest::All)?
+        .filter_map(Result::ok)
+        .map(|(id, job)| (JobId::from(id), job))
+        // Jobs with no runs have no timestamp (`None`), so any job with run
+        // activity sorts ahead of them.
+        .max_by_key(|(_, job)| job.latest().map(|(_, _, run)| *run.timestamp()).max())
+        .ok_or(error::Latest::NoJobs)
+}
+
 /// Resolve a Git revision, such as a shorthand OID, to a full commit OID.
 fn revparse(repo: &Repository, rev: &str) -> Result<Oid, error::Revparse> {
     repo.backend
@@ -385,8 +408,12 @@ mod command {
         /// Format output in a more human oriented way than JSON.
         #[clap(long)]
         pub pretty: bool,
+        /// Show the most recently active job instead of one for a revision.
+        #[clap(long, conflicts_with = "rev")]
+        pub latest: bool,
         /// Git revision for the commit, such as a full or shorthand OID.
-        pub rev: String,
+        #[clap(required_unless_present = "latest")]
+        pub rev: Option<String>,
     }
 
     /// Record a new run for an existing job COB.
@@ -439,10 +466,20 @@ mod error {
         Revparse(#[from] Revparse),
         #[error(transparent)]
         Find(#[from] Find),
+        #[error(transparent)]
+        Latest(#[from] Latest),
         #[error("failed to show job, could not serialize to JSON")]
         Json(#[source] serde_json::Error),
     }
 
+    #[derive(Debug, Error)]
+    pub enum Latest {
+        #[error("failed to list jobs")]
+        All(#[source] cob::store::Error),
+        #[error("no jobs found in this repository")]
+        NoJobs,
+    }
+
     #[derive(Debug, Error)]
     #[error("failed to resolve Git revision {rev}")]
     pub struct Revparse {