pub fn squash_branch(
    repo_path: &str,
    branch_refname: String,
    upstream_spec: String,
) -> Result<String, SquishError>Expand description
Squash a branch onto an upstream branch, replacing the branch history with a single commit.
§Arguments
- repo_path- Path to the git repository
- branch_refname- The branch to squash (e.g., “refs/heads/feature”)
- upstream_spec- The upstream to rebase onto (e.g., “main” or “origin/main”)
§Returns
A success message on completion, or a SquishError if the operation fails.