SRE-2507 common: do not report "Doc-only: true" for empty commit

[grom72]

Empty commit shall not be treated as Doc-only: true

Fix the problem introduced by #444:

https://build.hpdd.intel.com/job/daos-stack/job/daos/job/daily-2.6-testing/114/console

14:00:27  + TARGET_BRANCH=daily-2.6-testing
14:00:27  + set -uex
14:00:27  + git fetch origin daily-2.6-testing
14:00:27  From https://github.com/daos-stack/daos
14:00:27   * branch                daily-2.6-testing -> FETCH_HEAD
14:00:27  + git diff --no-commit-id --name-only origin/daily-2.6-testing HEAD
14:00:27  + grep -v -e '^docs/' -e '\.md$' -e '^.*LICENSE.*$'
14:00:27  Stage "Test" skipped due to when conditional

[grom72]

To be removed before landing.

[phender]

It looks like it should work for the *-testing branches. Do we want some similar logic in the ci/doc_only_change.sh file in the daos master/release branches to allow emty commity PRs to run tests w/o a commit pragma?

[grom72]

It looks like it should work for the *-testing branches. Do we want some similar logic in the ci/doc_only_change.sh file in the daos master/release branches to allow emty commity PRs to run tests w/o a commit pragma?

Not yet. But let's wait until 2.6.1 is ready.