fix(purge): restore cursor and temp files on any exit path (#915)

[sebastianbreguel]

Summary

Fixes #915 (mo purge leaves the terminal cursor hidden after running).

bin/purge.sh hid the cursor before perform_purge and restored it via a single trailing show_cursor. Under set -euo pipefail, any abort path other than INT/TERM (e.g. an uncaught error inside perform_purge, a non-zero return, SIGHUP from closing the terminal) skipped that line, so the terminal stayed with the cursor invisible until the user ran tput cnorm themselves.

While fixing that I noticed the main()-scoped trap 'show_cursor; exit 130' INT TERM overwrote the existing file-scope trap cleanup_temp_files EXIT INT TERM. So a Ctrl-C during arg parsing (before perform_purge reinstalled its own trap) would also leak temp files — addressed as part of the same change.

Fix

Fold show_cursor into the file-scope cleanup function alongside cleanup_temp_files, and reinstall the traps in the same shape bin/installer.sh already uses (trap cleanup EXIT + an INT/TERM trap that explicitly calls cleanup before exit 130). The EXIT trap is the catch-all, so every exit path — normal, set -e abort, or signal — runs cleanup exactly once.

Diff is +7 / −6 in a single file.

-# Set up cleanup trap for temporary files
-trap cleanup_temp_files EXIT INT TERM
+# Restores cursor and clears temp files even when set -e aborts (#915).
+cleanup() {
+    show_cursor 2> /dev/null || true
+    cleanup_temp_files
+}
+trap cleanup EXIT
+trap 'trap - EXIT; cleanup; exit 130' INT TERM

…and the corresponding deletions inside main() (the redundant in-main() INT/TERM trap and the trailing show_cursor).

Why mirror installer.sh rather than clean.sh

The repo has three cleanup shapes today (installer.sh, clean.sh, uninstall.sh). installer.sh is the closest cousin to purge.sh — interactive UI, cursor hide/show, temp files, no need to pass the signal name to cleanup. Matching it keeps the variance between files lower.

Test plan

• shellcheck bin/purge.sh — clean
• bats tests/purge.bats tests/purge_config_paths.bats — 76/76 pass
• bash bin/purge.sh --help — parses
• Walked the worst case mentally: Ctrl-C mid-perform_purge → handle_interrupt runs show_cursor and exit 130 → exit fires the file-scope EXIT trap → cleanup calls show_cursor (idempotent) and cleanup_temp_files. Both windows (before and during perform_purge) are covered.

Not in scope

bin/clean.sh and bin/uninstall.sh already wrap show_cursor inside a file-scope cleanup, so they are not affected by this bug. Keeping this PR narrow to #915.

[tw93]

@sebastianbreguel Thanks for the careful fix. Merged into main; this covers #915 and also keeps temp cleanup intact on exit paths.