windmill-labs/windmill · error

git branch -m ${newName} failed (exit ${r.status}): ${r.stde

Error message

git branch -m ${newName} failed (exit ${r.status}): ${r.stderr ?? ""}

What it means

renameCurrentGitBranch runs `git branch -m <newName>` via spawnSync to rename the current branch in place (used by `wmill workspace fork --from-branch` to turn the working branch into a wm-fork/<base>/<id> branch). If git exits non-zero, the helper throws this error including the exit code and git's stderr. It means git itself refused the rename; no fork branch was created.

Source

Thrown at cli/src/utils/git.ts:44

    "git",
    ["show-ref", "--verify", "--quiet", `refs/heads/${branchName}`],
    { stdio: "pipe" },
  );
  return r.status === 0;
}

/**
 * Rename the currently checked-out branch (`git branch -m <newName>`). Used by
 * `wmill workspace fork --from-branch` to turn an existing working branch into
 * the `wm-fork/<base>/<id>` fork branch in place, preserving its commits.
 */
export function renameCurrentGitBranch(newName: string): void {
  const r = spawnSync("git", ["branch", "-m", newName], {
    encoding: "utf8",
    stdio: "pipe",
  });
  if ((r.status ?? 1) !== 0) {
    throw new Error(
      `git branch -m ${newName} failed (exit ${r.status}): ${r.stderr ?? ""}`,
    );
  }
}

export function getOriginalBranchForWorkspaceForks(branchName: string | null): string | null {
  if (!branchName || !branchName.startsWith(WM_FORK_PREFIX)) {
    return null
  }

  const start = branchName.indexOf("/") + 1;
  const end = branchName.lastIndexOf("/");

  if (start < 0 || end < 0 || end - start <= 0) {
    return null
  }

  return branchName.slice(start, end)

View on GitHub (pinned to e474e8803c)

Solutions

1. Run the command from inside a git working tree (`git rev-parse --is-inside-work-tree` to confirm).
2. Check the stderr in the message for git's specific complaint and fix it (e.g. invalid characters in the generated branch name).
3. Commit or stash if git state blocks the rename, then retry `wmill workspace fork`.
4. Verify the target branch name is valid: `git check-ref-format --branch <newName>`.
5. Ensure git is installed and on PATH.

Example fix

// before: run outside a repo
$ cd /tmp && wmill workspace fork --from-branch
// Error: git branch -m wm-fork/main/abc failed (exit 128): fatal: not a git repository
// after
$ cd ~/my-project && wmill workspace fork --from-branch

import { spawnSync } from "node:child_process";
function canRenameBranchHere(): { ok: boolean; reason?: string } {
  const inRepo = spawnSync("git", ["rev-parse", "--is-inside-work-tree"], { encoding: "utf8" });
  if (inRepo.status !== 0 || inRepo.stdout?.trim() !== "true") return { ok: false, reason: "not inside a git work tree" };
  return { ok: true };
}

function isBranchNameValid(name: string): boolean {
  const r = spawnSync("git", ["check-ref-format", "--branch", name], { stdio: "pipe" });
  return r.status === 0;
}

try {
  renameCurrentGitBranch(newName);
} catch (e) {
  if (String(e).includes("git branch -m")) {
    console.error(`Branch rename refused: ${e.message}. Are you inside a git repo and is '${newName}' a valid branch name?`);
  }
  throw e;
}

When it happens

Trigger: Calling createWorkspaceFork/renameCurrentGitBranch outside a git repository (exit 128, 'not a git repository'), when newName is empty/invalid as a branch name (exit 128, 'fatal: not a valid branch name'), or any other git-level refusal of `branch -m`.

Common situations: Running `wmill workspace fork` outside a git repo or in a bare checkout; a workspace/fork id that produces an invalid branch name (spaces, invalid chars); detached HEAD or unusual git state; git not installed is not this error (that would surface as r.error instead).

Understand the failure class

Background: "git command failed": what it means when a tool shells out to git and git exits non-zero — this error's family across 21 libraries.

Related errors

• You can only create forks within a git repo. Forks are track
• Could not get git branch name
• --from-branch is for converting a *different* working branch
• Refusing to rename your current branch \`${currentBranch}\`
• Refusing to rename your current branch \`${currentBranch}\`

AI-assisted analysis of windmill-labs/windmill@e474e8803c (2026-09-03). Data as JSON: /api/errors/8d3ffcaa99271e9d. Report an issue: GitHub.