Exit status

Code	Meaning
0	Success.
1	An error: a connection failure, a file that does not parse, a plan that cannot be computed, a statement that fails during apply, or drift under apply-from.
2	plan --check or diff --check found executable DDL, or fmt --check found a file that is not formatted.
80	A usage error: an unknown flag, a missing argument, or two options that conflict.

A skipped drop is not executable DDL. A plan that contains nothing else exits with 0 under --check. The output is the same with and without the flag.

pista plan --check schema.sql
echo $?  # 0: no changes, 2: changes, 1: error