MergeChain: PR merge dependencies

Merge dependencies for GitHub pull requests: block a PR until the PRs it depends on merge first. Cross-repo and transitive chains.

MergeChain brings GitLab-style merge-request dependencies to GitHub pull requests. Declare that one PR must merge before another, and MergeChain shows the dependency status right above the merge box and disables the merge button until every prerequisite has landed. - Declare "Blocked by" / "Blocks" relationships from a single inline control - Transitive chains (A → B → C) with cycle detection - Cross-repo dependencies (owner/repo#123) - Reverse "depend on this" view, with one-click flip and remove - Choose where the block appears (top, bottom, left gutter, or sidebar) - No backend: dependency data is stored in the PR description; your token stays in your browser and only ever contacts GitHub Note: the merge block is enforced in your browser; teammates without the extension can still merge. Install the companion GitHub App (or use a token) to read and update PRs. Not affiliated with or endorsed by GitHub, Inc.