fix: hive-forge agit pr-create sets multi-line body via rest patch

hive-forge/src/verbs/pr_create.rs

@@ -17,6 +17,9 @@
 //! is a read-only collaborator who can't push branches. Re-running with
 //! the same `--topic` updates the open PR. This is the path agents use
 //! to contribute to `internal/knowledge`; pair it with `hive-forge clone`.
+//! A multi-line `--body` can't ride as a git push option (the wire
+//! protocol forbids newlines there), so it's pushed title-only and the
+//! body is set on the resulting PR via a REST PATCH.
 
 use std::process::{Command, Stdio};
 
@@ -82,7 +85,7 @@ pub struct Args {
 pub fn run(client: &Client, args: Args) -> Result<()> {
     let body = body::resolve(args.body.as_deref(), args.body_file.as_deref())?.unwrap_or_default();
     if args.agit {
-        return agit_create(&args, &body);
+        return agit_create(client, &args, &body);
     }
     // Normal REST flow. `--head` is required (clap enforces it unless
     // `--agit`), so unwrap is safe here.
@@ -116,12 +119,24 @@ pub fn run(client: &Client, args: Args) -> Result<()> {
 /// `force-push=true` lets a re-run with the same topic UPDATE the open
 /// PR (the new commit branches from base's tip, which the forge sees as
 /// non-fast-forward against the existing PR head and rejects without it).
-fn agit_create(args: &Args, body: &str) -> Result<()> {
+///
+/// The git wire protocol forbids newline characters in push options, so
+/// a multi-line `description=` would make the push fail outright. A
+/// single-line body still rides along as a push option (it's guaranteed
+/// to land even if we can't parse the PR URL back out); a multi-line
+/// body is pushed title-only and then set on the resulting PR via a REST
+/// PATCH, mirroring the manual `pr-create --title …` + `issue-edit
+/// --body-file` two-step.
+fn agit_create(client: &Client, args: &Args, body: &str) -> Result<()> {
     let remote = args.remote.as_deref().unwrap_or("origin");
     let topic = match &args.topic {
         Some(t) => t.clone(),
         None => current_branch().unwrap_or_else(|| "contribution".to_owned()),
     };
+    // A body with any newline can't be a push option; defer it to a REST
+    // PATCH after the push. A single-line body is safe inline.
+    let inline_body = !body.is_empty() && !body.contains('\n');
+    let deferred_body = !body.is_empty() && body.contains('\n');
     let refspec = format!("HEAD:refs/for/{}/{topic}", args.base);
     let mut push_args = vec![
         "push".to_owned(),
@@ -134,7 +149,7 @@ fn agit_create(args: &Args, body: &str) -> Result<()> {
         "-o".to_owned(),
         "force-push=true".to_owned(),
     ];
-    if !body.is_empty() {
+    if inline_body {
         push_args.push("-o".to_owned());
         push_args.push(format!("description={body}"));
     }
@@ -149,20 +164,51 @@ fn agit_create(args: &Args, body: &str) -> Result<()> {
     if !output.status.success() {
         anyhow::bail!("`git push {remote}` (AGit) failed:\n{stderr}");
     }
-    if let Some(url) = parse_pr_url(&stderr) {
-        println!("{url}");
-    } else {
+    let Some(url) = parse_pr_url(&stderr) else {
         // Push landed but no PR URL in the sideband — surface the raw
         // remote output so the caller can find the link themselves.
         eprint!("{stderr}");
+        if deferred_body {
+            eprintln!(
+                "warning: multi-line body NOT set — PR URL not parsed, so it could \
+                 not be PATCHed. Set it manually: hive-forge issue-edit <pr#> --body-file -"
+            );
+        }
         println!(
             "AGit push to refs/for/{}/{topic} succeeded (PR URL not parsed from output above)",
             args.base
         );
+        return Ok(());
+    };
+    if deferred_body {
+        if let Some(number) = pr_number_from_url(&url) {
+            let repo = client.repo();
+            client
+                .patch_json(
+                    &format!("/repos/{repo}/issues/{number}"),
+                    &json!({ "body": body }),
+                )
+                .with_context(|| format!("set body on AGit PR #{number}"))?;
+        } else {
+            eprintln!(
+                "warning: multi-line body NOT set — could not parse PR number from {url}. \
+                 Set it manually: hive-forge issue-edit <pr#> --body-file -"
+            );
+        }
     }
+    println!("{url}");
     Ok(())
 }
 
+/// Extract the PR index from a Forgejo PR URL (`…/pulls/<n>`). Returns
+/// `None` if the last path segment isn't a number.
+fn pr_number_from_url(url: &str) -> Option<u64> {
+    url.trim_end_matches('/')
+        .rsplit('/')
+        .next()
+        .and_then(|seg| seg.parse().ok())
+}
+
 /// Current git branch name (`git rev-parse --abbrev-ref HEAD`), or
 /// `None` on detached HEAD / error.
 fn current_branch() -> Option<String> {
@@ -308,6 +354,28 @@ remote:   http://forge.example/internal/knowledge/pulls/7\n";
         assert_eq!(parse_pr_url("To http://localhost:3000/x/y.git\n"), None);
     }
 
+    #[test]
+    fn pr_number_parses_trailing_index() {
+        assert_eq!(
+            pr_number_from_url("http://forge.example/internal/knowledge/pulls/42"),
+            Some(42)
+        );
+        // tolerant of a trailing slash
+        assert_eq!(
+            pr_number_from_url("http://forge.example/org/repo/pulls/7/"),
+            Some(7)
+        );
+        // not a number → None (caller falls back to the manual-edit hint)
+        assert_eq!(
+            pr_number_from_url("http://forge.example/org/repo/pulls/"),
+            None
+        );
+        assert_eq!(
+            pr_number_from_url("http://forge.example/org/repo/compare"),
+            None
+        );
+    }
+
     #[test]
     fn strips_create_pr_hint_block() {
         let stderr = "\