GitoxideLabs/gitoxide · error

is not a commit ID prefix

Error message

{value:?} is not a commit ID prefix

What it means

`resolve_commit` validates that a todo value looks like a commit ID abbreviation: at least 4 ASCII hex characters. If the token given to a `pick`, `squash`, or `fork` heading is shorter than 4 characters or contains non-hex characters, parsing fails with this error before any repository lookup is attempted.

Solutions

1. Use at least a 4-character hex prefix of the commit ID (a full ID also works).
2. Fix typos: the token must match `^[0-9a-fA-F]{4,}$`.
3. Copy the ID from the generated todo or `git log` output instead of typing it manually.

Example fix

// before
pick abc fix the thing

// after
pick 1a2b3c4d fix the thing

// Rust: validate a todo ID token before building the todo line
fn is_commit_id_prefix(v: &str) -> bool {
    v.len() >= 4 && v.bytes().all(|b| b.is_ascii_hexdigit())
}

fn as_commit_id_prefix(value: &str) -> Option<&str> {
    let v = value.trim();
    (v.len() >= 4 && v.bytes().all(|b| b.is_ascii_hexdigit())).then_some(v)
}

match resolve_commit(&repo, value) {
    Ok(id) => use_id(id),
    Err(e) if e.to_string().contains("is not a commit ID prefix") => {
        eprintln!("{value:?} must be >=4 hex chars; copy the ID from the generated todo.");
        Err(e)
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: Calling `parse` with todo lines whose ID token is e.g. `abc` (too short), contains typos like `1a2b3c4g`, is an empty string after `split_whitespace`, or is a branch name/subject rather than a hex ID.

Common situations: Hand-editing the todo and typing a too-short abbreviation; pasting a shortstat or message word where the ID belongs; locales/editors mangling hex characters.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• an editable commit is not connected to the selected base
• the rebase todo contains more than one @ command
• an empty commit needs a title
• the rebase todo has no fork heading
• the last fork section contains no commits

AI-assisted analysis of GitoxideLabs/gitoxide@e73179060b (2026-09-08). Data as JSON: /api/errors/6e76b47db2b6410a. Report an issue: GitHub.

Appendix: source

Thrown at gix-tix/src/edit/todo.rs:1063

    let checkout = checkout_target.map(|target| rebase::PlanCheckout {
        target,
        reference: checkout_reference,
    });
    Ok(Some(Parsed {
        plan: rebase::Plan {
            base: state.onto,
            scope: state.scope,
            steps,
            checkout,
            expected_refs: state.expected_refs,
        },
        tips: state.tips,
    }))
}

fn resolve_commit(repo: &gix::Repository, value: &str) -> Result<ObjectId> {
    if value.len() < 4 || !value.bytes().all(|byte| byte.is_ascii_hexdigit()) {
        anyhow::bail!("{value:?} is not a commit ID prefix");
    }
    let id = repo
        .rev_parse_single(value)
        .with_context(|| format!("could not resolve commit ID {value:?}"))?;
    id.object()
        .context("could not load a todo object")?
        .try_into_commit()
        .context("a todo ID does not name a commit")?;
    Ok(id.detach())
}

fn parse_ref_line(line: &str) -> Result<Vec<(bool, BString)>> {
    let body = line
        .strip_prefix('(')
        .and_then(|line| line.strip_suffix(')'))
        .context("a reference line must be enclosed in parentheses")?;
    let mut ranges = Vec::new();
    let mut start = 0;

View on GitHub (pinned to e73179060b)