Conditionally Run Workflows Based on Git Artifact Files Changed

[tony-mw]

Summary

It would be useful to add a key:list(values) option to the git artifact stanza of the Workflow/Workflow-Template CRD where an operator can specify the paths of files that, when modified, will trigger the workflow.

• Example:

artifacts:
  - name: my-git-repo
    path: "/home/argo"
    git:
      repo: "my-repo.git"
      depth: n
      filter:
        watchPaths:
          - service1/*

Use Cases

I ran into a scenario where I needed this functionality to set a working directory for a later stage in my workflow, based on the files changed in the repo. That was specifically for a Terraform workflow, but I could see this also being useful in monorepos containing multiple microservices where builds should only happen when code specific directories has changed.

I was able to achieve this by developing a custom go program that leverages the go-git package to derive file changes that occur when an Event triggers a Workflow. This runs as a pre-build stage in the workflow currently, and passes the working directories from one stage to the next.

Here is a snippet of my code which is triggered if the event is a pull request that I think could likely be a good starting point to add this feature. (If the event is just a commit to main or any branch that builds, there is less logic because you only have to compare the 2 latest commits instead of every ancestor of main)

	ref, _ := repo.Log(&git.LogOptions{
		From:  myBranchRef,
	})

	ref.ForEach(func(c *object.Commit) error {
		ancestor, _ := c.IsAncestor(currentCommit)
		if logger.Check() {
			log.Printf("Is ancestor: %t", ancestor)
		}
		if ancestor {
			appendOn = false
			return nil
		}
		if appendOn {
			commits = append(commits, c)
		}
		return nil
	})

	for _, v := range commits {
		diff, err := v.Patch(currentCommit)
		if err != nil {
			log.Fatal(err)
		}
		filesPatched := diff.FilePatches()
		for _, fileList := range filesPatched {
			if fileList.IsBinary() {
				log.Println("Ignoring binary files")
				continue
			}
			from, to := fileList.Files()
			if from.Path() == to.Path() {
				filesChanged = append(filesChanged, from.Path())
			} 
		}
	}

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[terrytangyuan]

Use Argo Events to setup a GitHub event source: https://github.com/argoproj/argo-events/blob/master/docs/eventsources/setup/github.md

And then trigger a Argo workflow: https://github.com/argoproj/argo-events/blob/master/docs/sensors/triggers/argo-workflow.md

[tony-mw]

Right, that works in GitHub... but the problem is that some source control tools don't send you which files change in their event

[terrytangyuan]

File event source might be what you want: https://github.com/argoproj/argo-events/blob/master/docs/eventsources/setup/file.md

[OneCricketeer]

File event source might be what you want

Am I missing some context? How would this help with Git event trigger?