Create git output that updates git

[bobcatfish]

Expected Behavior

As discussed in #1076, if a git PipelineResource is used as an output, this should cause a change in the outside world, i.e. for git the most appropriate action would be to create a new git commit. And in #1279 we want to make PipelineResoruces immutable, i.e. using a resource as a output would create a new PipelineResource.

This would mean that any Task that has a git PipelineResource output should:

1. Create a new PipelineResource instance
2. Create a commit in the backing git repo (it would have to have permission to push to that repo)

Actual Behavior

At the moment a git PipelineResource basically acts like a PVC only when used as an output (i.e. a way to share files). In #1109 we'll remove that functionality.

Additional Info

Blocked on design decisions in #1279

[ghost]

The pipeline resources revamp described by #1673 proposes a solution to this issue by allowing customisation of a resource's behaviour when in rw/create mode. So, for example, the catalog's hypothetical Git resource could include an RW mode that git pushes back to the remote repo, writes out the SHA that was pushed, and allows other tasks in a pipeline to rely on those resources.

I'm going to link to this from that epic so that we can track support of this feature as part of that work.

[tekton-robot]

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[tekton-robot]

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[tekton-robot]

@tekton-robot: Closing this issue.

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