Triggering tasks on Semver change: triggers jobs out or order - concourse

Question

Here's what I'm trying to achieve:
I have a project with a build job for a binary release. The binary takes a while to cross-compile for each platform, so I only want to release build to be done when a release is tagged, but I want the local-native version to build and tests to run for each checked-in version.
Based on the flight-school demo... so far, my pipeline configuration looks like this:
resources:
- name: flight-school
type: git
source:
uri: https://github.com/nbering/flight-school
branch: master
- name: flight-school-version
type: semver
source:
driver: git
uri: https://github.com/nbering/flight-school
branch: master
file: version
jobs:
- name: test-app
plan:
- get: flight-school
trigger: true
- task: tests
file: flight-school/build.yml
- name: release-build
plan:
- aggregate:
- get: flight-school-version
trigger: true
- get: flight-school
passed: [test-app]
- task: release-build
file: flight-school/ci/release.yml
This produces a pipeline in the Web UI that looks like this:
The problem is that when I update the "release" file in the git repository, the semver resource, "flight-school-version" can check before the git resource "flight-school", causing the release build to be processed from the git version assigned to the previous check-in.
I'd like a way to work around this so that the release build appears as a separate task, but only triggers when the version is bumped.
Some things I've thought of so far
Create a separate git resource with a tag_filter set so that it only runs when a semver tag has been push to master
Pro: Jobs only run when tag is pushed
Con: Has the same disconnected-inheritance problem for tests as the semver-based example above
Add the conditional check for a semver tag (or change diff on a file) using the git history in the checkout as part of the build script
Pro: Will do basically what I want without too much wrestling with Concourse
Con: Can't see the difference in the UI without actually reading the build output
Con: Difficult to compose with other tasks and resource types to do something with the binary release
Manually trigger release build
Pro: Simple to set up
Con: Requires manual intervention.
Use the API to trigger a paused build step on completion of tests when a version change is detected
Con: Haven't seen any examples of others doing this, seems really complicated.
I haven't found a way to trigger a task when both the git resource and semver resource change.
I'm looking for either an answer to solve the concurrency problem in my above example, or an alternative pattern that would produce a similar release workflow.

Answer 1

Summary
Here's what I came up with for a solution, based on suggestions from the Concourse CI slack channel.
I added a parallel "release" track, which filters on tags resembling a semantic versioning versions. The two tracks share task configuration files and build scripts.
Tag Filtering
The git resource supports a tag_filter option. From the README:
tag_filter: Optional. If specified, the resource will only detect commits
that have a tag matching the expression that have been made against
the branch. Patterns are glob(7)
compatible (as in, bash compatible).
I used a simple glob pattern to match my semver tags (like v0.0.1):
v[0-9]*
At first I tried an "extglob" pattern, matching semantic versions exactly, like this:
v+([0-9]).+([0-9]).+([0-9])?(\-+([-A-Za-z0-9.]))?(\++([-A-Za-z0-9.]))
That didn't work, because the git resource isn't using the extglob shell option.
The end result is a resource that looks like this:
resource:
- name: flight-school-release
type: git
source:
uri: https://github.com/nbering/flight-school
branch: master
tag_filter: 'v[0-9]*'
Re-Using Task Definitions
The next challenge I faced was avoiding re-writing my test definition file for the release track. I would have to do this because all the file paths use the resource name, and I now have a resource for release, and development. My solution is to override the resource with an option on the get task.
jobs:
- name: test-app-release
plan:
- get: flight-school
resource: flight-school-release
trigger: true
- task: tests
file: flight-school/build.yml
Build.yml above is the standard example from the flight school tutorial.
Putting It All Together
My resulting pipeline looks like this:
My complete pipeline config looks like this:
resources:
- name: flight-school-master
type: git
source:
uri: https://github.com/nbering/flight-school
branch: master
- name: flight-school-release
type: git
source:
uri: https://github.com/nbering/flight-school
branch: master
tag_filter: 'v[0-9]*'
jobs:
- name: test-app-dev
plan:
- get: flight-school
resource: flight-school-master
trigger: true
- task: tests
file: flight-school/build.yml
- name: test-app-release
plan:
- get: flight-school
resource: flight-school-release
trigger: true
- task: tests
file: flight-school/build.yml
- name: build-release
plan:
- get: flight-school
resource: flight-school-release
trigger: true
passed: [test-app-release]
- task: release-build
file: flight-school/ci/release.yml

Answer 2

In my opinion you should manually click the release-build button, and let everything else be automated. I'm assuming you are manually bumping your version number, but it seems better to move that manual intervention to releasing.
What I would do is have put at the end of release-build that bumps your minor version. Something like:
- put: flight-school-version
params:
bump: minor
That way you will always be on the correct version, once you release 0.0.1, you are done with it forever, you can only go forward.