It's difficult to test the files comparison if it contains all its own
assertions, since you can only test successes. This commit rewrites
the helper to use a func without assertions, that can be more roundly
tested.
This adds another means of updating files to the package pkg/update/,
in setters.go (and gives the existing file a better name).
In passing, I changed the test util for comparing before/after
updates, in pkg/files/, to give a little more context when comparing
file contents; and, since the comparison between actual and expected
is not symmetrical, I corrected the order of the args in the tests.
This factors out the function that checks directories for equivalence,
and uses it to check that the upstream repo has the expected update
when the controller has pushed its commit.
Hidde Beydals
Michael Bridgen