# Given input files playbook.yaml and foo.yaml:

# playbook.yaml
---
# ...
- tasks:
  - include: tasks/foo.yaml tags=foo dir=/var/foo
    tags: frob

# foo.yaml
---
- action: command rm -fr $dir
  tags: [foo, ansible, rocks]
- action: command mkdir -p $dir
  tags: [bar, ansible, rocks]

# It would become:

# playbook.yaml
---
# ...
- tasks:
  - action: command rm -fr /var/foo
      tags: [frob, ansible, rocks, foo]

# $dir was substituted with the args_spec in the initial include
# statement and became /var/foo

# 'frob' comes from the initial tagging applied to the include statement

# 'foo', 'ansible', and 'rocks' come from the tagging applied to the
# action definition in foo.yaml