pub fn resolve_ref_to_commit(repo_path: &Path, git_ref: &str) -> Result<String>Expand description
Resolves a git ref (commit, branch, tag) to its full commit SHA.
Equivalent to git -C <repo> rev-parse <ref>^{commit}. Used by diff
callers to short-circuit when both refs resolve to the same commit
(the worktree-build + graph-build pipeline is expensive on large
repositories — HEAD HEAD against a kernel-scale tree blew the
90s CLI / 120s MCP deadlines before this helper was wired in).
§Errors
Returns GitError::NotFound if git is not in PATH,
GitError::CommandFailed if the ref cannot be resolved (unknown ref,
or a tag that does not point at a commit), and GitError::InvalidOutput
if git returned non-UTF-8 or empty stdout.