Adding merge types to repository resource

[taiidani]

Adding merge types to the GitHub Repository resource so that users can control when the repository allows Squash merges, Rebase merges and/or Merge commits.

Imported from hashicorp/terraform#15230
Fixes hashicorp/terraform#15183
Fixes #14

[josephholsten]

sans whitespace: https://github.com/terraform-providers/terraform-provider-github/pull/1/files?w=1

[josephholsten]

Seems boring an reasonable!

[taiidani]

Hey -- boring? This was my first contribution to Terraform! Far from boring!

[josephholsten]

"Exciting" code scares me. I'll take boring any day!

I think we're waiting on the provider migration to finish and then this can get merged.

[stack72]

Hi @taiidani

Thanks for the work here - I had to make 1 change to the tests. When i ran the tests in their form, I got the following:

=== RUN   TestAccGithubRepository_importBasic
--- FAIL: TestAccGithubRepository_importBasic (0.32s)
	testing.go:428: Step 0 error: Error applying: 1 error(s) occurred:

		* github_repository.foo: 1 error(s) occurred:

		* github_repository.foo: POST https://api.github.com/orgs/terraformtesting/repos: 422 Repository creation failed. [{Resource:Repository Field: Code:custom Message:Either :allow_merge_commit, :allow_squash_merge or :allow_rebase_merge must be true}]

So I updated the tests :)

Thanks

Paul