Add --batch option as an alternative to STDIN

[rolandwalker]

Description

Add --batch option as an alternative to STDIN, factoring out a statements_from_filehandle() function which can also be used to improve the functionality of the source command.

The initial behavior when both STDIN is not-a-tty and --batch is in effect is to warn, and use --batch. Similarly, the priority of the --execute option was clarified with warnings. These may be revisited: we could consider different behavior, as well as exiting with an error in case of warning.

Motivation: display of a prompt_toolkit progress bar during batch execution. If the input is from STDIN, we can't know how many statements are the goal, at least without creating a tempfile. As mentioned above, this also lays the basis to improve the source command, which reads the entire file into memory.

Checklist

• I added this contribution to the changelog.md file.
• I added my name to the AUTHORS file (or it's already there).
• To lint and format the code, I ran

  uv run ruff check && uv run ruff format && uv run mypy --install-types .

[github-actions]

No correctness or security regressions stood out in the PR diff.

Residual testing gaps (worth adding before merge):

1. Missing coverage for --batch - (explicit STDIN path), including precedence behavior when STDIN is non-tty.

   • Relevant logic: main.py:2565

2. Missing coverage for the new MAX_MULTILINE_BATCH_STATEMENT guard raising ValueError in the factored parser.

   • Relevant logic: batch_utils.py:14

3. No direct unit tests for statements_from_filehandle() splitting behavior across multi-statement input and trailing non-terminated statement.

   • Relevant logic: batch_utils.py:8

I couldn’t run tests locally because pytest/uv aren’t installed in this environment.