CI: modify behaviour of tag "%ci:reset-backlog"

Now it will build current commit and skip anything else.

.cirrus.yml

@@ -30,12 +30,11 @@ build_task:
   # Determine changes in repository and build modified packages.
   build_script: |
     if grep -qiP '^\s*%ci:reset-backlog\s*$' <(git log --format="%B" -n 1 "$CIRRUS_CHANGE_IN_REPO"); then
-        # If commit message contains line '%ci:reset-backlog', no builds
-        # should be done and CI should stop with "green" status.
-        MODIFIED_PACKAGES=""
-    else
-        MODIFIED_PACKAGES=$(./scripts/build/ci/determine_git_changes.sh)
+        # If commit message contains line '%ci:reset-backlog', builds will be done
+        # only for current commit.
+        unset CIRRUS_LAST_GREEN_CHANGE
     fi
+    MODIFIED_PACKAGES=$(./scripts/build/ci/determine_git_changes.sh)
     for package in $MODIFIED_PACKAGES; do
         if [ -n "$CIRRUS_PR" ]; then
             # Perform full builds for PR.
@@ -72,10 +71,9 @@ publish_task:
   # Publish.
   upload_to_bintray_script: |
     if grep -qiP '^\s*%ci:reset-backlog\s*$' <(git log --format="%B" -n 1 "$CIRRUS_CHANGE_IN_REPO"); then
-        MODIFIED_PACKAGES=""
-    else
-        MODIFIED_PACKAGES=$(./scripts/build/ci/determine_git_changes.sh)
+        unset CIRRUS_LAST_GREEN_CHANGE
     fi
+    MODIFIED_PACKAGES=$(./scripts/build/ci/determine_git_changes.sh)
     if [ -n "$MODIFIED_PACKAGES" ]; then
         for arch in aarch64 arm i686 x86_64; do
             curl -s -o "/tmp/debs-${arch}.tar.gz" "http://$CIRRUS_HTTP_CACHE_HOST/debs-${arch}-${CIRRUS_CHANGE_IN_REPO}"