-- Forks and pull requests. Applied by store/migrate.rs.
-- A pull request is an issues row with kind = 'pull' (shared numbering); this table holds the
-- branch, head and mergeability state. head_repo_id is NULL once the head repo is deleted.

ALTER TABLE repos ADD COLUMN fork_of TEXT REFERENCES repos(id);

CREATE TABLE pull_requests (
    issue_id       TEXT PRIMARY KEY REFERENCES issues(id) ON DELETE CASCADE,
    base_branch    TEXT NOT NULL,
    head_repo_id   TEXT REFERENCES repos(id),     -- NULL if the head repo was deleted
    head_branch    TEXT NOT NULL,
    head_oid       TEXT NOT NULL,                 -- last known head commit (also refs/pull/N/head)
    base_oid       TEXT NOT NULL,                 -- base branch tip when mergeability was last computed
    merge_base     TEXT,
    mergeable      TEXT NOT NULL DEFAULT 'unknown', -- 'unknown' | 'clean' | 'conflict' | 'merged' | 'up_to_date'
    conflict_files TEXT NOT NULL DEFAULT '[]',    -- JSON array of paths
    merged_at      TEXT,
    merged_by      TEXT REFERENCES users(id),
    merge_commit   TEXT,
    allow_maintainer_edits INTEGER NOT NULL DEFAULT 1);
CREATE INDEX pull_requests_head ON pull_requests(head_repo_id, head_branch);