Triggers based on changes to TestSource

[gberche-orange]

Is your feature request related to a problem? Please describe.

As a testkube test author,
In order to get feedback on changes to my test content when I commit and push them in git
I need to be able to configure a TestTrigger against a TestSource

Describe the solution you'd like

apiVersion: tests.testkube.io/v1
kind: TestTrigger
metadata:
  name: Kubernetes object name
  namespace: Kubernetes object namespace
spec:
  source: # trigger test based on changes to TestSource
    kind: TestSource
    # Any commits that contain the string [ci skip] will be ignored. This allows you to commit to your repository without triggering a new version.
    name: my-git-repo
    paths: # Optional. If specified (as a list of glob patterns), only changes to the specified files will trigger 
    ignore_paths: # Optional. The inverse of paths; changes to the specified files are ignored.
    tag_filter: # Optional. If specified, the resource will only trigger when new commits that have a tag matching the expression that have been made against the branch. Patterns are [glob(7)](http://man7.org/linux/man-pages/man7/glob.7.html) compatible (as in, bash compatible).
   tag_regex: # 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 [grep](https://www.gnu.org/software/grep/manual/grep.html) compatible (extended matching enabled, matches entire lines only). Ignored if tag_filter is also specified.

Note that the paths, ignore_paths, tag_filter and tag_regexp are inspired from similar triggers in https://github.com/concourse/git-resource built upon long year of CI/CD experience, including triggering tests from git changes

Note the tag_filter and tag_regexp would require an additional field on the TestSource resource:

• fetch_tags: Optional. If true the flag --tags will be used to fetch all tags in the repository. If false no tags will be fetched.

Meta data about the conditions that Triggered the test is mounted in /triggers

Specifically the TestSource last change is available in /trigger/source similar to https://github.com/concourse/git-resource#additional-files-populated

.git/committer: For committer notification on failed builds. This special file .git/committer which is populated with the email address of the author of the last commit. This can be used together with an email resource like [mdomke/concourse-email-resource](https://github.com/mdomke/concourse-email-resource) to notify the committer in an on_failure step.

.git/ref: Version reference detected and checked out. It will usually contain the commit SHA-1 ref, but also the detected tag name when using tag_filter or tag_regex.

.git/short_ref: Short (first seven characters) of the .git/ref. Can be templated with short_ref_format parameter.

.git/commit_message: For publishing the Git commit message on successful builds.

.git/commit_timestamp: For tagging builds with a timestamp.

.git/describe_ref: Version reference detected and checked out. Can be templated with describe_ref_options parameter. By default, it will contain the <latest annoted git tag>-<the number of commit since the tag>-g<short_ref> (eg. v1.6.2-1-g13dfd7b). If the repo was never tagged before, this falls back to a short commit SHA-1 ref.

Describe alternatives you've considered

Writing a new TestKube flux controller as suggested in #3026 to trigger TestKube tests based on Flux Source controller notifications. This would also solve the issue to trigger upon Flux kustomization changes #3712

This would leverage Flux GitRepository https://github.com/fluxcd/source-controller/blob/main/docs/spec/v1/gitrepositories.md might speed up implementation of this feature

Flux GitRepository properly supports the path/excludePath feature above, plus inclusion of nested git repos, optimized git clones, submodules, etc...

Support for tag rexgexp is being discussed in fluxcd/source-controller#341

[vsukhin]

@gberche-orange really interesting feature. going to work on it