circle.yml: deploy non-master branches

[alban]

By default, non-master branches are not deployed on the Docker Hub. With
this patch, you can enable this feature by setting the environment
variable DEPLOY_BRANCH in the circle configuration.

It will not be tagged with the "latest" tag but instead derive the tag
from the branch name. Since "/" are not allowed in Docker tag names, all
"/" are replaced by "-".

When testing code in Scope, I use circle to build the Docker image but I
don't want to always use my "master" branch for development.

/cc @alepuccetti

[tomwilkie]

ERROR: http://dl-4.alpinelinux.org/alpine/edge/testing: temporary error (try again later)
WARNING: Ignoring APKINDEX.24c95890.tar.gz: No such file or directory
ERROR: unsatisfiable constraints:
  runit (missing):
    required by: world[runit]
The command '/bin/sh -c echo "http://dl-4.alpinelinux.org/alpine/edge/testing" >>/etc/apk/repositories &&   apk add --update bash runit conntrack-tools iproute2 util-linux curl &&     rm -rf /var/cache/apk/*' returned a non-zero code: 1
make: *** [scope.tar] Error 1

Look like you need to hit retry, I'd guess this is a spurious error.

[alban]

Rebased on master (with #1534 merged). It seems to pass with the other mirror dl-3.alpinelinux.org.

[alban]

Updated. But the build fails now. I don't know why:

./common/sanitize ./probe ./probe/controls ./probe/docker ./probe/overlay ./xfer

can't load package: package github.com/weaveworks/scope/xfer: cannot find package "github.com/weaveworks/scope/xfer" in any of:

    /usr/local/go/src/github.com/weaveworks/scope/xfer (from $GOROOT)

    /go/src/github.com/weaveworks/scope/xfer (from $GOPATH)

Makefile:100: recipe for target 'tests' failed

[alban]

Rebased on master and Circle has built it fine.

[tomwilkie]

Thanks! Sorry I didn't get back to you; LGTM