fix: Date versions on UTC commit time, not build time

This is important so that package versions only advance when the sources
have changed, i.e. we only produce "new" packages if there is in fact
new content, which in turn prevents update churn when versions only go
up when there's something new.

scripts/build_debs.sh

@@ -45,7 +45,10 @@ git config --global --add safe.directory "$PWD"
 GIT_HEAD="$(git rev-parse HEAD)"
 
 KANIDM_VERSION="$(grep -ioE 'version.*' Cargo.toml | head -n1 | awk '{print $NF}' | tr -d '"' | sed -e 's/-/~/')"
-DATESTR="$(date +%Y%m%d%H%M)"
+# We read the commit date of the reference rev, feed it to date, format a bit and print in UTC.
+# Ergo, the version date field is a unix time representation of when the commit was submitted.
+# Unlike commit hashes, this is a sort compatible ever increasing version, but still marginally human readable.
+DATESTR="$(date -ud @$(git show --no-patch --format=%ct HEAD) +%Y%m%d%H%M)"
 GIT_COMMIT="${GIT_HEAD:0:7}"
 DEBIAN_REV="${DATESTR}+${GIT_COMMIT}"
 PACKAGE_VERSION="${KANIDM_VERSION}-${DEBIAN_REV}"