no-commit-to-branch does not respect excludes

Reproduction steps .pre-commit-config.yaml:

repos:
  - repo: 'https://github.com/pre-commit/pre-commit-hooks'
    rev: 'v3.1.0'
    hooks:
      - id: 'no-commit-to-branch'
        args: ['--branch', 'master']
        exclude: 'foo.txt'

git status:

$ git status
On branch master

No commits yet

Changes to be committed:
  (use "git rm --cached <file>..." to unstage)
	new file:   foo.txt

Output:

 $ pre-commit run
Don't commit to branch...................................................Failed
- hook id: no-commit-to-branch
- exit code: 1

Appreciate this might be somewhere between a bug and a feature request. The particular use-case I’m trying to address concerns a repo with a structure of:

.
├── application-code
│   └── code-which-must-be-peer-reviewed
└── integration-test-code
    └── test-code-which-can-go-straight-to-master

So I was expecting the following to work:

  - id: 'no-commit-to-branch'
    args: ['--branch', 'master']
    exclude: '^integration-test-code/'

This also applies to exclude_types. I believe the fix would be just to revert https://github.com/pre-commit/pre-commit-hooks/commit/66eb9d3aec1237b5aae3785b22da6b2f699b5d54 (EDIT: and drop the always_run) but I’m sure there was a good reason for that change, so wanted to check that before raising a PR. Many thanks!

[asottile]

would you like to send a PR with some documentation updates for the next person? maybe some quick blurb about ignoring files / exclude / types / exclude_types unless you set always_run: false (and the limitation about empty commits)

[marcjay]

Sounds good to me! Done in #501