Fix unbound variable error in column existence checks

[burakkurkcu]

Summary

Fixes an unbound variable error that could occur during database migration when the column-existence checks in init_db received non-numeric input.

Problem

The migration logic for adding ram_mb, base_name, and ssh_user columns used:

has_base_name=$(sqlite3 "$DB_FILE" "PRAGMA table_info(instances);" | grep -c 'base_name') || true
if [[ "$has_base_name" -eq 0 ]]; then
    ...
fi

The -eq operator evaluates both sides in arithmetic context, which treats bare words as variable names. If the captured value ever contained something non-numeric (e.g. a path like /Users/... leaking into the pipeline), bash would parse Users as a variable reference and — with set -u active — fail with:

db.sh: line 69: Users: unbound variable

The || true fallback was also masking genuine sqlite3 failures, letting migrations silently no-op.

Fix

• Introduced a column_exists helper that relies on grep -q's exit status, avoiding arithmetic context entirely.
• Anchored the grep pattern as |column| to match against pipe-delimited PRAGMA table_info output and prevent false matches on column name prefixes (e.g. ram_mb matching ram_mb_limit).
• Replaced all three has_* checks with if ! column_exists instances <col>.
• Removed the || true fallbacks so real sqlite3 errors surface instead of being swallowed.

Testing

• Fresh init on a new $DB_FILE — all three columns created as expected.
• Re-running against an already-migrated DB — no-ops cleanly, no errors.
• Running against a pre-migration DB missing all three columns — migrations apply correctly.
• Verified set -u no longer trips on the migration path.

Risk

Low. Pure refactor of internal migration logic; no schema or API changes. The new helper is private to db.sh.

[webcoyote]

Hi, and thanks for creating a PR for this issue. Can you help me understand the problem? I'm not sure how user data would infect the grep operation because the PRAGMA command is not performing a select on the table data, it's getting back a list of the column names, and grep then counts.

❯ sqlite3 "$DB_FILE" "PRAGMA table_info(instances);"
0|name|TEXT|0||1
1|vm_name|TEXT|1||0
2|ram_mb|INTEGER|0||0
3|created_at|TEXT|0|datetime('now')|0
4|base_name|TEXT|0||0
5|ssh_user|TEXT|0||0

Can you help me repro this error in db.sh line 69?

[burakkurkcu]

I remember I was at v1.0.11 version then pulled v1.0.18 it was silent exiting at time, then reverted to v1.0.11 again for time. and then seeing @echthesia addressing bug I have I pulled v1.0.21 and it was fine. then I pulled today latest commit with merge tart message, I started getting error below.

To be honest I didn't get it as it seems just a thing from migration side code which should just pass by because I already migrated before. so I threw db.sh to claude to try a quick fix to get going at first. and this is it. after error gone these logs occured.

when I have some more time I can try same repro path by reverting to .11 create vm and everything, and then to latest commit in today to see if it can repro.