Numbered Issue branches after a merged or closed PR

src/branch.rs

@@ -8,7 +8,8 @@ use crate::github::{self, PrState, PullRequest};
 use crate::issue::IssueUrl;
 
 pub enum Selection {
-    /// No Issue branch has been used yet: start `branch` from the Base branch.
+    /// No Issue branch has been used yet, or the highest-numbered one's PR is
+    /// merged or closed: start `branch` from the Base branch.
     Fresh { branch: String },
     /// `branch` is on origin, with no PR or the open `pr`.
     Continuation {
@@ -49,8 +50,8 @@ impl Selection {
 }
 
 /// Pick the Issue branch for `issue` from the Issue branches on origin (one
-/// `git ls-remote`) and their PRs in any state (one `gh pr list`). Fails if a
-/// local copy of the chosen branch in the launch repository differs from
+/// `git ls-remote`) and their PRs in any state (one `gh pr list`): the
+/// highest number seen on either decides. Fails if a local copy of the chosen branch in the launch repository differs from
 /// origin's: the Run replaces it and deletes it at cleanup.
 pub fn select(launch: &Git, issue: &IssueUrl) -> Result<Selection> {
     let first_branch = branch_name(issue, 1);
@@ -96,17 +97,17 @@ pub fn select(launch: &Git, issue: &IssueUrl) -> Result<Selection> {
         .into_iter()
         .find_map(|(number, sha)| (number == highest).then_some(sha));
     match (origin_sha, pr) {
-        (Some(origin_sha), pr) if pr.as_ref().is_none_or(|pr| pr.state == PrState::Open) => {
+        // A merged or closed PR uses its number up, even if its branch was deleted.
+        (_, Some(pr)) if pr.state != PrState::Open => {
+            let next = branch_name(issue, highest + 1);
+            check_local_branch(launch, &next, None)?;
+            Ok(Selection::Fresh { branch: next })
+        }
+        (Some(origin_sha), pr) => {
             check_local_branch(launch, &branch, Some(&origin_sha))?;
             Ok(Selection::Continuation { branch, pr })
         }
-        (_, pr) => bail!(
-            "{branch} can't be continued ({}), and numbered Issue branches are not supported yet",
-            match pr {
-                Some(pr) => format!("its PR {} is {}", pr.url, pr.state),
-                None => "it is gone from origin".to_string(),
-            }
-        ),
+        (None, _) => bail!("{branch} has an open PR but is gone from origin"),
     }
 }
 

tests/numbered_branches.rs

@@ -0,0 +1,205 @@
+//! Numbered Issue branches: once the highest-numbered Issue branch's PR is
+//! merged or closed, a Run starts fresh on the next number,
+//! `issue-<n>-branch-<k+1>`, from the Base branch.
+
+mod support;
+
+use support::Scenario;
+
+/// The agent commits its work and opens a PR for `branch` against `main`.
+fn agent_commits_and_opens_pr_for(branch: &str) -> String {
+    format!(
+        r#"
+echo "feature" > feature.txt
+git add feature.txt
+git commit -q -m "Add feature"
+gh pr create --base main --head {branch} --title "Add feature" --body "Closes #7"
+"#
+    )
+}
+
+#[test]
+fn a_merged_issue_branch_starts_a_fresh_run_on_branch_2_from_the_base_branch() {
+    let scenario = Scenario::new();
+    scenario.origin_has_branch("issue-7", "main", &["Earlier work"]);
+    scenario.github_has_pr("issue-7", "main", "MERGED");
+    scenario.agent_does(&agent_commits_and_opens_pr_for("issue-7-branch-2"));
+
+    let result = scenario.run(&[&scenario.issue_url(7)]);
+
+    assert_eq!(result.code, Some(0), "stderr: {}", result.stderr);
+    assert_eq!(result.stdout, "https://github.com/acme/widgets/pull/2\n");
+    assert_eq!(scenario.claude_calls()[0]["branch"], "issue-7-branch-2");
+    assert_eq!(
+        scenario.origin_log("issue-7-branch-2"),
+        Some(vec![
+            "Add feature".to_string(),
+            "Initial commit".to_string()
+        ])
+    );
+    assert_eq!(
+        scenario.origin_log("issue-7").map(|log| log.len()),
+        Some(2),
+        "the merged branch was touched"
+    );
+    scenario.assert_cleaned_up("issue-7-branch-2");
+}
+
+#[test]
+fn the_next_numbered_branch_gets_the_fresh_prompt() {
+    let scenario = Scenario::new();
+    scenario.origin_has_branch("issue-7", "main", &["Earlier work"]);
+    scenario.github_has_pr("issue-7", "main", "MERGED");
+    scenario.agent_does(&agent_commits_and_opens_pr_for("issue-7-branch-2"));
+
+    scenario.run(&[&scenario.issue_url(7)]);
+
+    let prompt = scenario.first_prompt();
+    assert!(
+        prompt.contains(
+            "\nPush branch issue-7-branch-2 and create a pull request against main using /thirdshift:pr, marked ready for review.\n"
+        ) && !prompt.contains("You are continuing work"),
+        "prompt: {prompt}"
+    );
+}
+
+#[test]
+fn a_closed_unmerged_issue_branch_starts_a_fresh_run_on_branch_2() {
+    let scenario = Scenario::new();
+    scenario.origin_has_branch("issue-7", "main", &["Abandoned work"]);
+    scenario.github_has_pr("issue-7", "main", "CLOSED");
+    scenario.agent_does(&agent_commits_and_opens_pr_for("issue-7-branch-2"));
+
+    let result = scenario.run(&[&scenario.issue_url(7)]);
+
+    assert_eq!(result.code, Some(0), "stderr: {}", result.stderr);
+    assert_eq!(scenario.claude_calls()[0]["branch"], "issue-7-branch-2");
+    assert_eq!(
+        scenario.origin_log("issue-7-branch-2"),
+        Some(vec![
+            "Add feature".to_string(),
+            "Initial commit".to_string()
+        ])
+    );
+}
+
+#[test]
+fn a_merged_issue_branch_deleted_from_origin_is_not_reused() {
+    let scenario = Scenario::new();
+    scenario.github_has_pr("issue-7", "main", "MERGED");
+    scenario.agent_does(&agent_commits_and_opens_pr_for("issue-7-branch-2"));
+
+    let result = scenario.run(&[&scenario.issue_url(7)]);
+
+    assert_eq!(result.code, Some(0), "stderr: {}", result.stderr);
+    assert_eq!(scenario.claude_calls()[0]["branch"], "issue-7-branch-2");
+    assert_eq!(scenario.origin_log("issue-7"), None);
+    assert_eq!(
+        scenario.origin_log("issue-7-branch-2"),
+        Some(vec![
+            "Add feature".to_string(),
+            "Initial commit".to_string()
+        ])
+    );
+}
+
+#[test]
+fn an_open_pr_on_branch_2_after_a_merged_issue_branch_is_continued() {
+    let scenario = Scenario::new();
+    scenario.github_has_pr("issue-7", "main", "MERGED");
+    scenario.origin_has_branch("issue-7-branch-2", "main", &["Earlier work"]);
+    let pr = scenario.github_has_pr("issue-7-branch-2", "main", "OPEN");
+    scenario.agent_does(
+        r#"
+git commit -q --allow-empty -m "Continue the work"
+"#,
+    );
+
+    let result = scenario.run(&[&scenario.issue_url(7)]);
+
+    assert_eq!(result.code, Some(0), "stderr: {}", result.stderr);
+    assert_eq!(result.stdout, format!("{pr}\n"));
+    assert_eq!(scenario.claude_calls()[0]["branch"], "issue-7-branch-2");
+    let prompt = scenario.first_prompt();
+    assert!(
+        prompt.contains("You are continuing work on branch issue-7-branch-2")
+            && prompt.contains(&format!("Update PR {pr} using /thirdshift:pr")),
+        "prompt: {prompt}"
+    );
+    assert_eq!(
+        scenario.origin_log("issue-7-branch-2"),
+        Some(vec![
+            "Continue the work".to_string(),
+            "Earlier work".to_string(),
+            "Initial commit".to_string(),
+        ])
+    );
+}
+
+#[test]
+fn a_merged_branch_2_starts_branch_3() {
+    let scenario = Scenario::new();
+    scenario.github_has_pr("issue-7", "main", "MERGED");
+    scenario.origin_has_branch("issue-7-branch-2", "main", &["Earlier work"]);
+    scenario.github_has_pr("issue-7-branch-2", "main", "MERGED");
+    scenario.agent_does(&agent_commits_and_opens_pr_for("issue-7-branch-3"));
+
+    let result = scenario.run(&[&scenario.issue_url(7)]);
+
+    assert_eq!(result.code, Some(0), "stderr: {}", result.stderr);
+    assert_eq!(result.stdout, "https://github.com/acme/widgets/pull/3\n");
+    assert_eq!(scenario.claude_calls()[0]["branch"], "issue-7-branch-3");
+    assert_eq!(
+        scenario.origin_log("issue-7-branch-3"),
+        Some(vec![
+            "Add feature".to_string(),
+            "Initial commit".to_string()
+        ])
+    );
+}
+
+#[test]
+fn a_merged_branch_2_deleted_from_origin_is_not_reused() {
+    let scenario = Scenario::new();
+    scenario.github_has_pr("issue-7", "main", "MERGED");
+    scenario.github_has_pr("issue-7-branch-2", "main", "MERGED");
+    scenario.agent_does(&agent_commits_and_opens_pr_for("issue-7-branch-3"));
+
+    let result = scenario.run(&[&scenario.issue_url(7)]);
+
+    assert_eq!(result.code, Some(0), "stderr: {}", result.stderr);
+    assert_eq!(scenario.claude_calls()[0]["branch"], "issue-7-branch-3");
+    assert_eq!(scenario.origin_log("issue-7-branch-2"), None);
+}
+
+#[test]
+fn the_pr_comes_from_the_numbered_branch_and_closes_the_issue() {
+    let scenario = Scenario::new();
+    scenario.github_has_pr("issue-7", "main", "MERGED");
+    scenario.agent_does(&agent_commits_and_opens_pr_for("issue-7-branch-2"));
+
+    let result = scenario.run(&[&scenario.issue_url(7)]);
+
+    assert_eq!(result.code, Some(0), "stderr: {}", result.stderr);
+    let prs = scenario.gh_state()["prs"].as_array().unwrap().clone();
+    let pr = prs.last().unwrap();
+    assert_eq!(pr["head"], "issue-7-branch-2");
+    assert_eq!(pr["base"], "main");
+    assert_eq!(pr["state"], "OPEN");
+    assert!(
+        pr["body"].as_str().unwrap().contains("Closes #7"),
+        "pr: {pr}"
+    );
+}
+
+#[test]
+fn a_local_copy_of_the_next_numbered_branch_stops_the_run() {
+    let scenario = Scenario::new();
+    scenario.github_has_pr("issue-7", "main", "MERGED");
+    scenario.launch_git(&["branch", "issue-7-branch-2"]);
+    scenario.agent_does(&agent_commits_and_opens_pr_for("issue-7-branch-2"));
+
+    let result = scenario.run(&[&scenario.issue_url(7)]);
+
+    scenario.assert_rejected_before_any_work(&result, "issue-7-branch-2 is not on origin");
+}