Issue 1182: Add sslVerify flag to pipelineresource type git

[dibbles]

Changes

Enables the disabling in git config of http.sslVerify such that the git fetch can succeed against local gitlab installs with self signed certificates by specifying sslVerify as "false" in the pipelineresource.

Fixes #1182

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Release Notes

The sslVerify parameter is now available on PipelineResource's of type git. This property defines whether http.sslVerify should be set to true or false in the global git config. Setting the property to false will disable certificate validation during the running of the git fetch against the git server and will be of use to people hosting git servers with self signed certificates.
The parameter sslVerify defaults to true if omitted.

Example usage:

apiVersion: tekton.dev/v1alpha1
kind: PipelineResource
metadata:
  name: wizzbang-git
  namespace: default
spec:
  type: git
  params:
    - name: url
      value: https://github.com/wizzbangcorp/wizzbang.git
    - name: revision
      value: master
    - name: sslVerify
      value: "false"

[dibbles]

I noted the existing issue after I had written the code ...... I also have noted there are a number of other issues about git config parameters but thought as I has the code for this one option, I might as well open the pull request to garner interest on taking the change until other solutions might become available.

[dibbles]

For reference:- #1182 was found after coding - adding link/comment here.

[dibyom]

A few minor comments but overall looks great :D A couple requests:

• Are you sure that go.mod needed to change?
• Could you add release notes to your PR description describing this new feature? (e.g. https://github.com/tektoncd/pipeline/blob/master/.github/pull_request_template.md#release-notes)

[dibbles]

Will look over dibyo's review tomorrow

[dibyom]

Thanks @dibbles !!
The go.mod change still seems to be in...is that needed?

[vdemeester]

/lgtm
Yeah the go.mod changes are… inherent… for some reason they should have been done in the go.mod PR.. no biggies 👼

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dibyom, vdemeester

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