support ignorePaths to exclude removal of certain files

[cppforlife]

Describe the problem/challenge you have

in some cases it's useful to retain certain temp files among fetched directories. (e.g. temp files generated by tools that were operating on top of fetched files.)

Describe the solution you'd like

add ignorePaths key on directory contents. ignorePaths would specify a set of globs that would be used to match in existing directories and copy them over on top of newly fetched sources.

apiVersion: vendir.k14s.io/v1alpha1
kind: Config
directories:
- path: components/terraform
  contents:
  - path: account-map
    git:
      url: https://github.com/cloudposse/terraform-aws-components
      ref: 0.137.0
    newRootPath: modules/account-map
    includePaths:
      - modules/account-map/**/*
    ignorePaths: &ignore
    - backend.tf.json
    - catalog/*

  - path: account-settings
    git:
      url: https://github.com/cloudposse/terraform-aws-components
      ref: 0.137.0
    newRootPath: modules/account-settings
    includePaths:
      - modules/account-settings/**/*
    ignorePaths: *ignore

Details:

• for directories that have been removed in newly fetched content, ignored content wont be retained
• files that already exist in newly fetched content will take precedence over files that copied from original directory.

[aknysh]

@cppforlife thank you.
The description sounds like what we need.

[aaronshurley]

Thanks for submitting this. We may not get to this soon but would accept contributions :)

[ewrenn8]

included in v0.20.0