"charm build" should not silently inherit README from base layers

[axinojolais]

Checklist

• [X] Confirmed this is an issue with charm-tools, not charmstore-client
• [X] Provide versions of tools used
• [X] Described the feature or ways to replicate the issue

What version am I running?

I ran the following command: snap info charm and got the following ouput:

$ snap info charm
name:      charm
summary:   charm and charm-tools
publisher: Cory Johns (johnsca)
contact:   [email protected]
license:   unset
description: |
  charmstore-client and charm-tools
commands:
  - charm
snap-id:      2Rryoc2ylScfbFl4eQtpntHD9iuZuMvt
tracking:     stable
refresh-date: today at 17:24 CEST
channels:
  stable:    2.4.4 (254) 47MB classic
  candidate: 2.4.4 (254) 47MB classic
  beta:      2.4.4 (254) 47MB classic
  edge:      2.4.4 (254) 47MB classic
installed:   2.4.4 (254) 47MB classic

I am using: Ubuntu 18.04

Issue/Feature

I expect/expected the following

The README (and README.md and README.txt etc) files provided by layers should renamed with the layer name appended, like copyright files

What I got

The README.md of the apt layer is present in the root directory of my built charm (see cs:~redis-charmers/redis - the layer is at https://github.com/omnivector-solutions/layer-redis)

[johnsca]

Your charm should provide a README.md file for the charm store to use, which would take precedence over any provided by a base layer. You could also use the ignore feature if you really need to. I'm not sure that it would be useful to include the layer READMEs in the built charm, whereas it is important from a legal perspective to include the layer copyrights.

[johnsca]

I'm leaning toward having a specific ReadmeTactic to disable inheriting that file from a base layer entirely and forcing the charm author to provide one.