mb0/salt — comment on commit 7818d52200c45fdb4a86abfd73ca03b334cf1fa8
File: salt/states/file.py line 321
By mb0:

you can use both 'context' and 'defaults' to easily extend the context variables:

/tmp/testfile:
file:
- managed
- source: salt://test/testfile
- template: jinja
- defaults:
greeting: Hello
greetee: World

extend:
/tmp/testfile:
file:
- context:
greeting: Hey