Comment workflow files

.github/workflows/apt.yml

@@ -1,3 +1,10 @@
+# This workflow runs on regular PR/push to branches
+# and is workflow_call'ed by nightly-unstable-package.yaml
+# schedule to build unstable release
+# The main purpose of the workflow to determine whether we need
+# to use "unstable" release_tag
+# The actual job dispatch is done by build-n-test-all-distros.yml
+
 name: Build
 
 on:

.github/workflows/build-n-test-all-distros.yml

@@ -1,4 +1,14 @@
 
+# This reusable workflow implements build and test workflow part and is for
+# calling from release automation and regular PR/push builds.
+#
+# It handles release_tag values, including empty one (empty means PR/push build)
+# and unstable.
+#
+# Unstable run requires explicit switching to unstable branch in each job and
+# action because the schedule is initiated from master branch but the target
+# branch should be unstable branch. This is also handled here.
+
 name: Build and Test All Distros
 
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