Automatically publish to the snap store from Travis

.travis.sh

#!/bin/sh -e

if [ -z "$SNAPCRAFT_SECRET" ]; then
    exit 0
fi

mkdir -p ".encrypted"
if [ ! -e ".encrypted/snapcraft.cfg.enc" ]; then
    echo "Seeding a new macaroon."
    echo "$SNAPCRAFT_CONFIG" > ".encrypted/snapcraft.cfg.enc"
fi

mkdir -p "$HOME/.config/snapcraft"
openssl enc -aes-256-cbc -base64 -pass env:SNAPCRAFT_SECRET -d -in ".encrypted/snapcraft.cfg.enc" -out "$HOME/.config/snapcraft/snapcraft.cfg"

if docker run -v $HOME:/root -v $(pwd):/cwd snapcore/snapcraft sh -c 'cd /cwd; snapcraft'; then
    if [ "${TRAVIS_BRANCH}" = "edge" ]; then
        docker run -v $HOME:/root -v $(pwd):/cwd snapcore/snapcraft sh -c "cd /cwd; snapcraft push *.snap --release edge"
    elif [ "${TRAVIS_BRANCH}" = "master" ]; then
        docker run -v $HOME:/root -v $(pwd):/cwd snapcore/snapcraft sh -c "cd /cwd; snapcraft push *.snap --release stable"
    fi
fi

openssl enc -aes-256-cbc -base64 -pass env:SNAPCRAFT_SECRET -out ".encrypted/snapcraft.cfg.enc" < "$HOME/.config/snapcraft/snapcraft.cfg"
rm -f "$HOME/.config/snapcraft/snapcraft.cfg"

.travis.yml

sudo: required
dist: trusty
services:
    - docker
cache:
    directories:
        - .encrypted
script:
    - ./.travis.sh

seed.sh

export SNAPCRAFT_SECRET=$(pwgen 20 -1)
export SNAPCRAFT_CONFIG="$(openssl enc -aes-256-cbc -base64 -pass env:SNAPCRAFT_SECRET < ~/.config/snapcraft/snapcraft.cfg)"
travis encrypt SNAPCRAFT_SECRET=$SNAPCRAFT_SECRET -a
travis env set SNAPCRAFT_CONFIG "$SNAPCRAFT_CONFIG"