INFENG-937: Publish Helm RCs

Add Helm makefile and CircleCI job to publish Helm chart release
candidates. This is necessary to properly deploy release candidates onto
the new release party cluster. Previously, bumpversion adjusted the
chart version in Chart.yaml and committed that to the release branch,
then rph used this in-tree version as a chart repository to do GKE
cluster upgrades during testing. This is no longer possible, though, so
we need to publish these release candidate versions. (We should probably
be doing this anyway, in the interest of transparency.)

This will create an additional GitHub release every time we cut a
release candidate.

.circleci/real_config.yml

@@ -1910,6 +1910,20 @@ jobs:
           command: make -C agent release-ee
       - run: mkdir /tmp/pkgs && cp -v */dist/*.{rpm,deb,tar.gz} /tmp/pkgs
 
+  publish-helm-gh-rc:
+    docker:
+      - image: <<pipeline.parameters.docker-image>>
+        environment:
+          GO111MODULE: "on"
+    steps:
+      - checkout
+      - attach_workspace:
+          at: .
+      - reinstall-go
+      - make-component:
+          component: helm
+          target: release-gh-rc
+
   publish-helm-gh:
     parameters:
       ee:
@@ -5575,6 +5589,12 @@ workflows:
           context: determined-production
           filters: *release-filters
 
+      - publish-helm-gh-rc:
+          requires:
+            - build-helm
+          context: determined-production
+          filters: *rc-filters
+
       - upload-try-now-template:
           context: determined-production
           filters: *release-filters

helm/Makefile

@@ -26,6 +26,18 @@ release-gh:
 	git clean -df
 	goreleaser --rm-dist
 
+.PHONY: release-gh-rc
+release-gh-rc: export GORELEASER_CURRENT_TAG := $(VERSION_TAG)
+# The following line lists all tags by creation date, finds the current tag and
+# the next line after, then prints that second line, which should be the most
+# recent previous tag. This works if the previous tag is both a minor release,
+# or an rc release.
+release-gh-rc: export GORELEASER_PREVIOUS_TAG := $(shell git tag --sort=-creatordate | grep "$(VERSION_TAG)" -A1 | sed -n '2 p')
+release-gh-rc:
+	go install github.com/goreleaser/[email protected]
+	git clean -df
+	goreleaser --rm-dist
+
 .PHONY: release-gh-dryrun
 release-gh-dryrun: export GORELEASER_CURRENT_TAG := $(VERSION_TAG)
 release-gh-dryrun: export GORELEASER_PREVIOUS_TAG := $(shell git tag --sort=-creatordate | grep -E '^[0-9.]+$$' | grep "$(VERSION_TAG)" -A1 | sed -n '2 p')