#!/bin/sh
# script/cibuild: run the CI build. The Dockerfile runs `make check`,
# so a successful build implies all checks pass. The Gitea workflow
# runs this on push.
#
# That implication only holds because of CHECK_EPOCH. Docker keys the
# `RUN make check` layer on content, so on an unchanged tree it is
# served from cache: the checks never execute and the build still exits
# 0. Passing a value that differs on every invocation invalidates that
# layer and everything below it, while the script/bootstrap toolchain
# layer above it keeps caching.
set -eu

ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"

main() {
    cd "$ROOT"
    # Assigned to a variable rather than substituted inline in the
    # argument list: a command substitution that fails inside an
    # argument does not trip `set -e`, so the inline form would quietly
    # pass an empty string and restore the cached false green. As the
    # whole of an assignment its exit status is the command's, so
    # `set -e` catches it. `%N` keeps two invocations within the same
    # second distinct; busybox date silently drops `%N` and still exits
    # 0, so `$$` is appended to cover that degradation.
    epoch="$(date +%s%N)$$"
    docker build --build-arg CHECK_EPOCH="$epoch" .
}

main "$@"