Repo config fetched from base only (#245)

Hubcast config settings for repos should only be fetched from the
default branch of the base repository. Previously, we were getting the
config from the head repo, which would lead to potential confusion for
users submitting PRs via forks.

This ensures that there is one source of settings for each repository.

I pulled this out of #240 to make for a faster review.

Author: cmelone

src/hubcast/web/github/routes.py

@@ -148,12 +148,13 @@ async def sync_pr(pull_request, gh, gl, gl_user, src_repo_private):
 
     src_repo_url = pull_request["head"]["repo"]["clone_url"]
     src_fullname = pull_request["head"]["repo"]["full_name"]
+    base_fullname = pull_request["base"]["repo"]["full_name"]
     want_sha = pull_request["head"]["sha"]
 
     # pull requests coming from forks are pushed as branches in the form of
     # pr-<pr-number> instead of as their branch name as conflicts could occur
     # between multiple repositories
-    is_pull_request_fork = src_fullname != pull_request["base"]["repo"]["full_name"]
+    is_pull_request_fork = src_fullname != base_fullname
     if is_pull_request_fork:
         target_ref = f"refs/heads/pr-{pull_request_id}"
     else:
@@ -172,7 +173,7 @@ async def sync_pr(pull_request, gh, gl, gl_user, src_repo_private):
         return
 
     # get the repository configuration from .github/hubcast.yml
-    repo_config = await get_repo_config(gh, src_fullname)
+    repo_config = await get_repo_config(gh, base_fullname)
     if not repo_config.draft_sync and pull_request["draft"]:
         if repo_config.draft_sync_msg:
             await gh.set_check_status(
@@ -252,21 +253,22 @@ async def sync_pr_event(event, gh, gl, gl_user, *arg, **kwargs):
 async def remove_pr(event, gh, gl, gl_user, *arg, **kwargs):
     pull_request = event.data["pull_request"]
     src_fullname = pull_request["head"]["repo"]["full_name"]
+    base_fullname = pull_request["base"]["repo"]["full_name"]
 
     # if the pull request comes from a fork we should clean up
     # the branch upon closing or merging the PR. However, if the
     # pull request comes from an internal branch we should wait
     # to clean up the branch when the branch is deleted from the
     # internal repository
-    is_pull_request_fork = src_fullname != pull_request["base"]["repo"]["full_name"]
+    is_pull_request_fork = src_fullname != base_fullname
     if not is_pull_request_fork:
         return
 
     pull_request_id = pull_request["number"]
     target_ref = f"refs/heads/pr-{pull_request_id}"
 
     # get the repository configuration from .github/hubcast.yml
-    repo_config = await get_repo_config(gh, src_fullname)
+    repo_config = await get_repo_config(gh, base_fullname)
 
     dest_fullname = f"{repo_config.dest_org}/{repo_config.dest_name}"
     dest_remote_url = f"{gl.instance_url}/{dest_fullname}.git"
@@ -328,17 +330,18 @@ async def respond_comment(event, gh, gl, gl_user, *arg, **kwargs):
 
         # get the branch this PR belongs to
         src_fullname = pull_request["head"]["repo"]["full_name"]
+        base_fullname = pull_request["base"]["repo"]["full_name"]
         # pull requests coming from forks are pushed as branches in the form of
         # pr-<pr-number> instead of as their branch name as conflicts could occur
         # between multiple repositories
-        is_pull_request_fork = src_fullname != pull_request["base"]["repo"]["full_name"]
+        is_pull_request_fork = src_fullname != base_fullname
         if is_pull_request_fork:
             branch = f"pr-{pull_request_id}"
         else:
             branch = pull_request["head"]["ref"]
 
         # get the gitlab repo information and run the pipeline
-        repo_config = await get_repo_config(gh, src_fullname, refresh=True)
+        repo_config = await get_repo_config(gh, base_fullname, refresh=True)
         dest_fullname = f"{repo_config.dest_org}/{repo_config.dest_name}"
         pipeline_url = await gl.run_pipeline(dest_fullname, branch)
 
@@ -359,17 +362,18 @@ async def respond_comment(event, gh, gl, gl_user, *arg, **kwargs):
 
         # get the branch this PR belongs to
         src_fullname = pull_request["head"]["repo"]["full_name"]
+        base_fullname = pull_request["base"]["repo"]["full_name"]
         # pull requests coming from forks are pushed as branches in the form of
         # pr-<pr-number> instead of as their branch name as conflicts could occur
         # between multiple repositories
-        is_pull_request_fork = src_fullname != pull_request["base"]["repo"]["full_name"]
+        is_pull_request_fork = src_fullname != base_fullname
         if is_pull_request_fork:
             branch = f"pr-{pull_request_id}"
         else:
             branch = pull_request["head"]["ref"]
 
         # get the gitlab repo information and run the pipeline
-        repo_config = await get_repo_config(gh, src_fullname, refresh=True)
+        repo_config = await get_repo_config(gh, base_fullname, refresh=True)
         dest_fullname = f"{repo_config.dest_org}/{repo_config.dest_name}"
         pipeline_id = await gl.get_latest_pipeline(dest_fullname, branch)