Change makefile allow specification of local/novel juju-gui branch.

[bac]

QA:

make clean - observe the directories releases and jujugui-deps do not exist.

make package - creates a releases and jujugui-deps directories. Ensure the releases/jujugui-1.9.6.tar.bz2 exists and jujugui-deps is populated with lots of wheels. Also note that in the output of the make command that juju-gui was pulled from github. You should see:

git clone --depth 1 --branch master https://github.com/juju/juju-gui.git

Now run make releases and observe it is a no-op.

Next ensure you can use a local branch for juju-gui, e.g.:

JUJU_GUI_BRANCH=$HOME/git/juju-gui make package

Again the tarball should be created but this time you'll git clone from the branch you specified. You'll see something like the following in the make output:

git clone --branch master /home/bac/git/juju-gui

Also, test that make clean unittest creates the tarball and runs the tests a-ok.

[jcsackett]

QAing this now.

[jcsackett]

QA notes:

Attempting to do the step JUJU_GUI_BRANCH= /home/jc/Code/canonical/juju-gui make package I get:

find . -name '*.pyc' -delete
rm -rf tests/.venv
rm -rf tests/download-cache
rm -rf jujugui-deps
rm -rf releases
make -C src package
make[1]: Entering directory `/home/jc/Code/charms/trusty/juju-gui/src'
rm -rf juju-gui
git clone --branch master /home/jc/Code/canonical/juju-gui/
Cloning into 'juju-gui'...
fatal: Remote branch master not found in upstream origin
fatal: The remote end hung up unexpectedly
make[1]: *** [juju-gui] Error 128
make[1]: Leaving directory `/home/jc/Code/charms/trusty/juju-gui/src'
make: *** [releases] Error 2

[jcsackett]

Once I checked out master into my repository, this worked; should this work with other branches, as the use case seems to me to be packaging local work?

[bac]

Good catch @jaycee. Could you grab the new revision and try again?

[jcsackett]

Code is :+1:; rechecking QA now.

[jcsackett]

QA OK.

[hatched]

:+1: This looks awesome! Thanks for this @bac

[bac]

:shipit: