opening-prs

What this skill does

# Opening PRs

A `flowing` graph that turns the imperative "create branch, push files,
open a PR, poll mergeable_state" workflow into a structural DAG. The
"NEVER push directly to main" rule is encoded as a `validate=` gate that
physically can't be skipped.

```python
from opening_prs import open_pr

result = open_pr(
    repo="owner/repo",
    branch_name="feat/cool-thing",
    title="Add cool thing",
    body="## Summary\n\n...",
    files=[
        ("src/cool.py", "<file content>"),
        ("docs/cool.md", "<file content>"),
    ],
    base="main",  # default; protected names are also rejected
)

print(result["pr_url"])             # https://github.com/.../pull/N
print(result["mergeable_state"])    # clean | dirty | unstable | behind | blocked
```

## What this fixes

The `gh pr create` workflow (or hand-rolled API calls) has five steps in
prose form:

1. Determine the branch name
2. Get the base branch's HEAD SHA
3. Create the branch
4. Push files to the branch
5. Create the PR
6. Poll `mergeable_state` until GitHub finishes computing it

Each step has known failure modes:

- **Step 1**: Accidentally pushing to `main` — the diagnosed pattern that
  motivated github-procedures §6 in the first place.
- **Step 6**: GitHub returns `mergeable_state: null` immediately after
  creation. Need to poll. "Wait a few seconds and check" is prose, not a
  procedure — so it gets skipped under context pressure.

This skill encodes both as flowing primitives:

```
determine_branch ──▶ guard ──▶ get_base_head ──▶ create_branch
                      │                              │
                      │                              ▼
                      │                        push_files
                      │                              │
                      │                              ▼
                      │                         create_pr
                      │                          /        \
                      │                         ▼          ▼
                      │                  wait_mergeable  present_pr [terminal]
                      │
                      └─ validate=must_not_be_base_branch
```

- **`validate=must_not_be_base_branch`** rejects `branch_name in
  {"main", "master", "trunk", "production", "prod"}` — case-insensitive
  — and the configured `base` itself. The body of `create_branch` never
  fires for a protected name. No GitHub API call happens for an
  invalid branch name.

- **`retry_until=lambda r: r["mergeable_state"] in SETTLED_STATES`**
  consumes the retry budget while GitHub computes the merge result.
  `unknown` and `null` keep polling; settled states (`clean`, `dirty`,
  `unstable`, `behind`, `blocked`) stop. Exhaustion is soft: the PR is
  still presented with the last observed state.

## Auth

Requires `GH_TOKEN` (or `GITHUB_TOKEN`) in the environment. Classic PAT
or fine-grained PAT with `repo` scope.

```python
import os
os.environ["GH_TOKEN"] = "ghp_..."   # or load from a .env file
```

The skill sends `User-Agent: opening-prs` on every API call. (GitHub
returns 401 "Bad credentials" without a UA, regardless of token
validity. Common trap.)

## Result shape

```python
{
    "pr_url": "https://github.com/owner/repo/pull/N",
    "pr_number": 42,
    "pr_state": "open",
    "branch": "feat/cool-thing",
    "base": "main",
    "head_sha": "abc123...",
    "mergeable_state": "clean",
    "files_pushed": ["src/cool.py", "docs/cool.md"],
    "detached_failures": [],
}
```

Raises `RuntimeError` only if the main DAG fails (validate, branch
creation, file push, or PR creation). Mergeable polling exhaustion is a
soft failure — the PR exists, the field just isn't computed yet.

## Tuning the mergeable poll

```python
open_pr(
    ...,
    mergeable_poll_retries=8,         # default 8
    mergeable_poll_base_ms=2000,      # default 2s
    mergeable_poll_max_ms=8000,       # default 8s (cap on exponential backoff)
)
```

## When NOT to use

- Pushing many large files (the GitHub Contents API is one-file-per-PUT
  with base64 encoding — slow above ~10 files). Use `git push` if you
  have the CLI.
- Needing to amend commits or rewrite history. This skill creates one
  commit per file via the contents API.
- Anything involving force-push, branch deletion, or PR review-state
  manipulation. Out of scope; use a different tool.

## See also

- `flowing` — the DAG runner this skill is built on
- `closing-issues` — the symmetric "close + synthesize" flow
- The `accessing-github-repos` skill for byte-layer GitHub access patterns