New-worktree base-branch selector is empty for multi-repo projects (reads the anchor, not the repo roots)

[stefanvandervelden-zipline]

The "From <branch>" selector in the new-worktree flow is empty for a .code-workspace project, so no base branch can be chosen.

BranchToolbarBranchSelector.tsx:139-140 sets branchCwd = activeWorktreePath ?? activeProject.workspaceRoot. For a workspace-file project workspaceRoot is the anchor — the directory holding the .code-workspace — which is usually not a git repo, so listBranches returns isRepo: false and the list is empty. (Same root cause shape as #112: a call site still reading workspaceRoot where multi-repo needs repoRoots.)

Beyond the empty list, there's a design question: one selector can't really serve N repos. My three roots have three different defaults — master, dev, and main — and the branch I actually want to base on exists in two of the three. A per-root base selection (defaulting each root to its own origin/HEAD) seems like what's needed, though I appreciate that's a bigger UX change than a one-line cwd fix.

WorktreeFanoutTarget already carries baseRef per target, so the fan-out layer looks like it supports this already — it's the UI that collapses it to a single value.

Version: multi-repo-workspaces @ 92de5d9a, macOS arm64, dev build.

[LoganRupe]

The blocker is fixed in b652075 on multi-repo-workspaces. Per-root base selection isn't — see below, so I'm leaving this open for it.

The impact was worse than an empty dropdown: sending is blocked without a base branch, so isolated runs were unusable for any .code-workspace project. Two bugs also sat behind the selector — the server matched repoRoot against the anchor projectCwd, which never matches for a workspace-file project, so the chosen base ref was silently dropped for every root; and startFromOrigin ran git fetch in the non-repo anchor, aborting the send. A shared resolveAnchorRepoRoot now backs both the selector and the worktree fan-out, and the existing origin/HEAD auto-default means it works without opening the dropdown at all.

Per-root base selection isn't done. WorktreeFanoutTarget does carry baseRef per target as you noted, but the collapse happens higher up in the prepareWorktree contract, which only holds a single baseBranch. That needs widening before the UI is worth building, so for now the chosen base applies to the anchor repo only and cousins branch off their own HEAD.

Note the branch is rebased onto upstream main periodically and force-pushed, so reset rather than pull. The pre-rebase tip is at multi-repo-workspaces-prerebase.