Skipping layers during build

[ktsakalozos]

When building the ibm-was-base layer [0]
I noticed that one of the layers to be merged were missing.
ibm-was-base uses layer ibm-im [1] which in turn uses ibm-base [2]. ibm-im is missing.

This is what it is happening. We first fetch the ibm-im layer in a temp directory under deps/layer/ https://github.com/juju/charm-tools/blob/master/charmtools/fetchers.py#L134 . Then we rename that temp directory to the name of the layer https://github.com/juju/charm-tools/blob/master/charmtools/fetchers.py#L58 (ibm-im). The InterfaceFetcher will extract https://github.com/juju/charm-tools/blob/master/charmtools/build/fetchers.py#L99 the last part of the repo path, wihich based on the interfaces entry [3] will be trunk and will rename the deps/layer/ibm-im to
deps/layer/trunk https://github.com/juju/charm-tools/blob/master/charmtools/build/fetchers.py#L110
The next layer is ibm-base whose path also ends with trunk. Therefore it will overwrite the ibm-im layer already in the deps/layer/trunk .

Should the layers and interfaces be declared in a way in the http://interfaces.juju.solutions/ so that we do not overwrite them while fetching or should we handle this in the charm-tools?

[0] http://bazaar.launchpad.net/~ibmcharmers/charms/trusty/layer-ibm-was-base/trunk/view/head:/layer.yaml
[1] https://launchpad.net/~ibmcharmers/charms/trusty/layer-ibm-im/trunk
[2] https://code.launchpad.net/~ibmcharmers/layer-ibm-base/trunk
[3] http://interfaces.juju.solutions/layer/ibm-im/

What version am I running?

I ran the following command: charm version and got the following ouput:

charm 2.2.0-0ubuntu1~ubuntu16.04.1~ppa2
charm-tools 2.1.4

I am using: Ubuntu Xenial