fix(create_project): make the write the branch-readiness gate (#42)

BranchExists returns true before the generated branch is writable, so
waitForBranch didn't help and a 2.5s retry budget was too short (branch became
writable ~30s post-generate under load in live testing). Drop waitForBranch;
let upsertRetry be the gate — retry the write on the transient "branch does not
exist" not-found for up to 60s, early-exit on success. Once the first write
lands the branch is writable and the rest succeed immediately. Refs #42.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/tools/create_project_from_template.go

@@ -151,12 +151,6 @@ func (t *CreateProjectFromTemplate) Call(ctx context.Context, raw json.RawMessag
 	}
 	result.DefaultBranch = branch
 
-	// Wait for the generated branch to become writable. gitea's /generate is
-	// async: it returns (and serves reads) before the branch ref is committed, so
-	// the first writes 404 "branch does not exist" for a beat. Poll until the
-	// branch is present.
-	t.waitForBranch(ctx, args.Owner, args.Name, branch)
-
 	// Substitute across the WHOLE tree: content in every blob, plus a path rename
 	// for any file whose path carries a placeholder (e.g. cmd/__PROJECT_NAME__/main.go).
 	// A fixed known-files list can't rename directories or cover every templated
@@ -192,27 +186,16 @@ func (t *CreateProjectFromTemplate) Call(ctx context.Context, raw json.RawMessag
 	return textOK(result)
 }
 
-// waitForBranch polls until the freshly-generated branch is present, or a short
-// budget elapses. Best-effort — upsertRetry covers the remaining read-vs-write
-// consistency window where the branch reads but does not yet write.
-func (t *CreateProjectFromTemplate) waitForBranch(ctx context.Context, owner, name, branch string) {
-	for i := 0; i < 20; i++ {
-		if ok, err := t.c.BranchExists(ctx, owner, name, branch); ok && err == nil {
-			return
-		}
-		select {
-		case <-ctx.Done():
-			return
-		case <-time.After(500 * time.Millisecond):
-		}
-	}
-}
-
-// upsertRetry retries UpsertFile through the brief post-generate window where the
-// branch is readable but writes still 404 "branch does not exist".
+// upsertRetry is the readiness gate for the async-generate branch race: gitea's
+// /generate returns (and serves reads) before the branch ref is committed, so the
+// first writes 404 "branch does not exist" until the initial commit lands (observed
+// up to ~30s under load). BranchExists is not a usable signal — it reports the
+// branch present before writes succeed. So the write itself is the probe: retry on
+// the transient not-found until it takes. Once the first write lands, the branch is
+// writable and the rest succeed on the first try.
 func (t *CreateProjectFromTemplate) upsertRetry(ctx context.Context, owner, name, path string, args gitea.UpsertFileArgs) error {
 	var err error
-	for i := 0; i < 5; i++ {
+	for i := 0; i < 60; i++ {
 		if _, err = t.c.UpsertFile(ctx, owner, name, path, args); err == nil {
 			return nil
 		}
@@ -222,7 +205,7 @@ func (t *CreateProjectFromTemplate) upsertRetry(ctx context.Context, owner, name
 		select {
 		case <-ctx.Done():
 			return err
-		case <-time.After(500 * time.Millisecond):
+		case <-time.After(time.Second):
 		}
 	}
 	return err

internal/tools/create_project_from_template_test.go

@@ -69,10 +69,6 @@ func (f *fakeTemplateServer) handler(t *testing.T, tmpl, dest string) http.Handl
 			_, _ = fmt.Fprintf(w, `{"name":%q,"full_name":"mathias/%s","default_branch":%q,"clone_url":"http://gitea.example.com/mathias/%s.git","html_url":"http://gitea.example.com/mathias/%s","template":false}`,
 				dest, dest, f.genBranch, dest, dest)
 
-		case r.Method == http.MethodGet && strings.HasPrefix(p, "/api/v1/repos/mathias/"+dest+"/branches/"):
-			// waitForBranch readiness probe — branch is present.
-			_, _ = fmt.Fprint(w, `{"name":"main","commit":{"id":"c"}}`)
-
 		case r.Method == http.MethodGet && strings.HasPrefix(p, "/api/v1/repos/mathias/"+dest+"/git/trees/"):
 			var entries []string
 			for path := range f.files {