Fixes#1539
The branch matcher feature has been introduced in #1383, but the current
implementation was broken and doesn't work at all (#1539).
If my understanding is correct, there are two problems:
(1) The `GlobalCfg` has a default `Repo` instance which always matches
any repositries and branches. Therefore the branch matcher never be
functional.
(2) Validating base branches in
`DefaultPreWorkflowHooksCommandRunner.RunPreHooks()` implicitly assumed
that users customize `pre_workflow_hooks`, but the assumption isn't
always true because it defaults to empty.
For (1), I added a new method `MatchingRepo()` to `GlobalCfg` to check
`BranchMatches()` for a single `Repo` instance.
For (2), I moved validating branch to
`DefaultCommandRunner.validateCtxAndComment()`. Since the method has
already validated meta data of pull request, I think it's suitable place
to check base branches, but please let me know if there is anywhere more
suitable.
* Add a branch regex to the repo.yaml config to allow Atlantis to
accept only pull requests with a given base branch (the branch
a PR would merge _into_).
* `branch` is optional. By default its unset and Atlantis will match
webhooks for pull requests for any branch (no change)
Match any PR,
```
repos:
- id: /.*/
branch: /.*/
```
Match only PRs with master or main base branch.
```
repos:
- id: /.*/
branch: /(main|master)/
```
Some repos have special pull request branching practices. For example,
plan/apply from feature branches merging into master, but separate flows
for merging master into a release branch (where Atlantis isn't used).
Adding a regex allows for flexible workflow options. For example, you
could have Atlantis ignore "release" branches.
