build-lectures: drop eval, quote path inputs (#36)

[mmcky]

Closes #36 (M10, L17, L22) — shell-safety cleanup of build-lectures.

M10 — drop eval, quote the path inputs

The build command was built by string interpolation and run through eval $BUILD_CMD, so a space or shell metacharacter in source-dir/output-dir would break the build. Now it invokes jb build directly:

jb build "$SOURCE_DIR" --path-output "$OUTPUT_DIR" "${builder_args[@]}" $EXTRA_ARGS

• source-dir/output-dir/builder/extra-args are passed via env: and the paths are quoted.
• builder-specific flags live in a bash array (builder_args), so no eval.
• the if/elif ladder became a case.

L17 — output-dir default ./ → .

Drops the cosmetic .//_build/html double-slash in the build path.

L22 — extra-args word-splitting (documented)

$EXTRA_ARGS is left unquoted on purpose so -W --keep-going splits into two flags. A comment in the step notes that quoted args with embedded spaces inside extra-args aren't supported (the standard CI caveat).

Verification

• YAML validated; bash -n clean on the new logic; no eval remains.
• Behavior preserved — flag order is irrelevant to jb, and each builder expands to the same command as before, e.g. pdflatex → jb build lectures --path-output . --builder pdflatex -n -W --keep-going.

Closes #36

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR hardens the build-lectures composite action’s shell invocation by removing eval, quoting path inputs, and restructuring builder selection to be safer and more predictable when paths contain spaces or shell metacharacters.

Changes:

• Replaces interpolated eval $BUILD_CMD with a direct jb build invocation using quoted path arguments and a builder_args bash array.
• Updates the output-dir default from ./ to . to avoid .//_build/... paths.
• Documents (in-step) that extra-args is intentionally word-split (unquoted) to allow multiple flags.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
build-lectures/action.yml	Drops eval, quotes path inputs via env vars, uses an array + case for builder flags, and adjusts output-dir default.
CHANGELOG.md	Adds an Unreleased entry describing the shell-safety changes and default tweak.