add pull request panel

crates/signed_state/src/repo.rs

@@ -297,6 +297,39 @@ impl RepoStore {
         self.send(builder, cx);
     }
 
+    /// Open a pull request on this repository: a root PR event whose content
+    /// is the `git format-patch` output of the proposed changes.
+    ///
+    /// The branch metadata (branch name, clone URL, merge base, root patch)
+    /// isn't known to the UI yet and is left empty; the proposed commit is
+    /// parsed from the patch's `From <commit>` header, falling back to an
+    /// empty hash for hand-written content.
+    pub fn open_pull_request(
+        &mut self,
+        subject: Option<String>,
+        content: String,
+        cx: &mut Context<Self>,
+    ) {
+        let current_commit = patch_current_commit(&content)
+            .and_then(|hex| hex.parse().ok())
+            .unwrap_or_else(|| bitcoin_hashes::Sha1::from_byte_array([0u8; 20]));
+
+        let builder = GitPullRequest {
+            repository: self.addr.clone(),
+            content,
+            subject,
+            labels: Vec::new(),
+            branch_name: None,
+            clone: Vec::new(),
+            current_commit,
+            root_patch_event: None,
+            merge_base: None,
+        }
+        .into_event_builder();
+
+        self.send(builder, cx);
+    }
+
     /// Send a root patch (`git format-patch` output) to this repository.
     pub fn send_root_patch(&mut self, patch: String, cx: &mut Context<Self>) {
         let Ok(root_marker) = Tag::parse(["t", "root"]) else {
@@ -356,3 +389,32 @@ where
 fn sort_newest_first(events: &mut [Event]) {
     events.sort_by_key(|e| std::cmp::Reverse(e.created_at));
 }
+
+/// The proposed commit of a `git format-patch` output: the `From <commit>`
+/// header on its first line.
+fn patch_current_commit(patch: &str) -> Option<&str> {
+    let line = patch.lines().next()?;
+    let hex = line.strip_prefix("From ")?;
+    hex.split_whitespace().next().filter(|hex| hex.len() == 40)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::patch_current_commit;
+
+    #[test]
+    fn parses_format_patch_header() {
+        let patch = "From 1f6c0c5f3f1a1a1a1a1a1a1a1a1a1a1a1a1a1a1a Mon Sep 17 00:00:00 2001\nFrom: A <a@b.c>\nSubject: [PATCH] fix\n\n---\n";
+        assert_eq!(
+            patch_current_commit(patch),
+            Some("1f6c0c5f3f1a1a1a1a1a1a1a1a1a1a1a1a1a1a1a")
+        );
+    }
+
+    #[test]
+    fn no_commit_without_header() {
+        assert_eq!(patch_current_commit(""), None);
+        assert_eq!(patch_current_commit("Subject: [PATCH] x\n\n---\n"), None);
+        assert_eq!(patch_current_commit("From short\n"), None);
+    }
+}