git-tools

/**
 * @const {string} Lowercase prefix git uses for fatal error messages on stderr.
 * @default "fatal:"
 */
const fatalPrefix = "fatal:"

/**
 * Cleans a simple-git error message and prefixes it with operation context so the
 * caller LLM gets actionable information about which tool failed and where.
 * Strips the noisy `fatal:` prefix that simple-git inherits from git's stderr,
 * collapses multi-line output into one line, and rewrites a few common error
 * patterns into clearer messages.
 *
 * @param operation The name of the failing tool (for example, `git_status`).
 * @param target The target the operation was acting on, such as a repo name or URL.
 * @param error The error caught from a simple-git call.
 * @returns A formatted error string suitable for returning to the model.
 */
export function formatGitError(operation: string, target: string, error: unknown): string {
  const rawMessage = error instanceof Error ? error.message : String(error)

  const cleaned = rawMessage
    .split("\n")
    .map(line => {
      const trimmed = line.trim()

      return trimmed.toLowerCase().startsWith(fatalPrefix) ? trimmed.slice(fatalPrefix.length).trim() : trimmed
    })
    .filter(line => line.length > 0)
    .join("; ")

  const lower = cleaned.toLowerCase()

  if (lower.includes("not a git repository")) {
    return `Error: "${target}" is not a git repository or the directory does not exist within the working directory.`
  }

  if (lower.includes("already exists and is not an empty directory")) {
    return `Error: ${operation} could not write to "${target}" because the destination already exists and is not empty. Choose a different repoName.`
  }

  if (lower.includes("could not resolve host") || lower.includes("could not read from remote")) {
    return `Error: ${operation} could not reach "${target}". Check the URL and that the network is available. Cause: ${cleaned}`
  }

  if (lower.includes("authentication failed") || lower.includes("permission denied")) {
    return `Error: ${operation} was denied access to "${target}". Authentication failed or the credentials lack permission.`
  }

  if (lower.includes("ambiguous argument") || lower.includes("bad object") || lower.includes("unknown revision")) {
    return `Error: ${operation} could not resolve the requested ref or path in "${target}". Cause: ${cleaned}`
  }

  const suffix = cleaned.length > 0 ? `: ${cleaned}` : ""

  return `Error: ${operation} failed for "${target}"${suffix}.`
}