Selective releasing (#708)

* Rejig the build process

During a build, we check and rebuild any dependencies prior to
potentially using them.

Build:
- DIND (this only produces a new docker image, no local code changes)
- fnserver (built as part of the testing)

On master, if everything works, then we release the built artifacts,
if necessary:
- DIND (this pushes a docker image and a tag)
- fnserver (this builds the docker image and releases it, if necessary).

Fnserver is dealt with last by the release script: all previous steps
in CI use locally-run go tests rather than a docker file.

When a commit happens, we need to know (a) if we need to rebuild
a set of tools and artifacts (or whether we can continue to use
published ones); and (b) if we need to release new versions of
those tools, if all tests pass.

We do this by identifying the previous release tag on origin/master
(which is the release branch), then checking for changes between
that point at the current one.

Those changes may appear in various places in the tree: some simple
boolean rules work out whether the change means we need to rebuild
and rerelease.

* Make the fnproject/fnserver build use the latest dind

As docker bumps from 17.12.x, use whatever dind we just built.

* Use bash

release.sh

@@ -15,27 +15,15 @@ else
   exit 1
 fi
 
-git pull
-
-version_file="api/version/version.go"
-if [ -z $(grep -m1 -Eo "[0-9]+\.[0-9]+\.[0-9]+" $version_file) ]; then
-  echo "did not find semantic version in $version_file"
-  exit 1
-fi
-perl -i -pe 's/\d+\.\d+\.\K(\d+)/$1+1/e' $version_file
 version=$(grep -m1 -Eo "[0-9]+\.[0-9]+\.[0-9]+" $version_file)
 echo "Version: $version"
 
-make docker-build
-
-git add -u
-git commit -m "$image: $version release [skip ci]"
-git tag -f -a "$version" -m "version $version"
+# Push the version bump and tags laid down previously
+gtag=$image-$version
 git push
 git push origin $version
 
-# Finally tag and push docker images
-docker tag $user/$image:latest $user/$image:$version
+# Finally, push docker images
 docker push $user/$image:$version
 docker push $user/$image:latest