Add replace rules in source definition

[olblak]

Sometimes it happens that a source returns unwanted strings and we want to remove a sub part.
An example, the release tag from https://github.com/Azure/azure-cli/releases prefix 'azure-cli-' to version name like azure-cli-2.9.1 but the docker image tag doesn't contain that 'azure-cli-'

So to automated tag update, we need to be able to remove such strings

source:
  kind: githubRelease
  replaces: 
    - from: "string"
      to: ""
    - from: "substring1"
      to: "substring2"
  spec:
    owner: "Github Owner"
    repository: "Github Repository"
    token: "Don't commit your secrets!"
    url: "Github Url"
    version: "Version to fetch"

Signed-off-by: Olivier Vernin olivier@vernin.me