chore: use changesets to support an automatic release process

[zbynekstara]

Description

A simpler version of #3445. Needs #3452 to work.

Use changesets for deferred versioning and changelog creation.

NOTE: Tags/Releases become per-package (@joint/core@4.4.0) instead of v4.3.1.

Motivation and Context

This will allow us to streamline our release process by asking PR contributors to make versioning and changelog decisions at PR time (when they have the most context about their changes) instead of at release time.

A changeset is a file inside .changesets/ folder (one per PR), which records two things:

• Which packages need a version bump due to this change, and if it is a patch/minor/major bump.
• What the changelog line for this change should say.

Example:

---
"@joint/core": minor
---

dia.Paper - add `originX` and `originY` options to `getFitToContentArea()`

Setup TODO

Before the Changesets release pipeline can run, these steps need to be completed:

• Add NPM_TOKEN to secrets, with publish rights for all eight public packages (we cannot use trusted publishing yet).
• Enable auto-merge (repo "Settings → Actions → General → Allow GitHub Actions to create and approve pull requests"). We may need to change GITHUB_TOKEN settings to make this work.

What to expect on the first run

The empty changeset currently in .changeset/ means the first push to master goes into version mode and opens a "Version Packages" PR whose only content is the deletion of that file — no version bumps. Merge it; select-mode then reports none (every version matches npm, which is exactly what the version/private fixes bought you) and nothing publishes. Real releases start with the next PR that carries a real changeset.

[Copilot]

Pull request overview

This PR introduces Changesets-based versioning/changelog management and a GitHub Actions release workflow for the JointJS monorepo, aiming to move release decisions (bump type + changelog entry) to PR time and automate package publishing from master.

Changes:

• Add Changesets tooling/configuration and a release pipeline (select-mode → version PR → publish).
• Start publishing per-package changelogs by adding CHANGELOG.md files and including them in package files lists.
• Update contribution/docs/templates and PR CI to require a changeset for releasable changes.

Reviewed changes

Copilot reviewed 24 out of 25 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
yarn.lock	Adds Changesets and related dependencies to the workspace lockfile.
package.json	Adds @changesets/cli as a root devDependency.
CONTRIBUTING.md	Documents the Changesets workflow and contributor requirements.
CLAUDE.md	Adds repo-level guidance to follow the Changeset format rules.
.github/pull_request_template.md	Adds a PR checklist item for changesets.
.github/workflows/test-pr.yml	Adds a CI step to enforce presence of a changeset for releasable changes.
.github/workflows/release.yml	Introduces a Changesets-driven release workflow for master pushes.
.changeset/README.md	Adds local documentation for the .changeset/ folder and format rules.
.changeset/config.json	Adds Changesets configuration (linked packages, changed file patterns, etc.).
.changeset/clear-maps-begin.md	Adds an initial empty changeset to force the first “version mode” run behavior.
packages/joint-core/package.json	Includes CHANGELOG.md in the published file set.
packages/joint-core/CHANGELOG.md	Adds the initial per-package changelog content for @joint/core.
packages/joint-react/package.json	Includes CHANGELOG.md in the published file set.
packages/joint-react/CLAUDE.md	Adds @joint/react-specific Changesets guidance and reflows text.
packages/joint-react/CHANGELOG.md	Adds the initial per-package changelog content for @joint/react.
packages/joint-layout-directed-graph/package.json	Adjusts version metadata and includes CHANGELOG.md in the published file set.
packages/joint-layout-directed-graph/CHANGELOG.md	Adds the initial per-package changelog content for @joint/layout-directed-graph.
packages/joint-layout-msagl/package.json	Adjusts version metadata and includes CHANGELOG.md in the published file set.
packages/joint-layout-msagl/CHANGELOG.md	Adds the initial per-package changelog content for @joint/layout-msagl.
packages/joint-eslint-config/package.json	Adjusts package version metadata.
packages/joint-decorators/package.json	Adjusts package version metadata, dependency range, and includes CHANGELOG.md in the published file set.
packages/joint-cli/package.json	Includes CHANGELOG.md in the published file set.
packages/joint-vitest-plugin-mock-svg/package.json	Includes CHANGELOG.md in the published file set.
packages/joint-shapes-general/package.json	Marks the package as private.
packages/joint-shapes-general-tools/package.json	Marks the package as private.

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[Copilot]

Pull request overview

Copilot reviewed 25 out of 26 changed files in this pull request and generated no new comments.

Suppressed comments (6)

packages/joint-react/CLAUDE.md:33

• The Jest CLI flag in this example uses --testPathPatterns, which isn’t a valid Jest option (Jest uses --testPathPattern).

# Run a single test file
yarn jest --testPathPatterns="use-elements"

packages/joint-cli/package.json:13

• files now includes ./CHANGELOG.md, but this file doesn’t exist in the package directory, so it won’t actually be included in the published tarball. Either add the changelog file (even a placeholder) or remove this entry until the file is introduced.

  "files": [
    "dist",
    "./CHANGELOG.md"
  ],

packages/joint-decorators/package.json:39

• files now includes ./CHANGELOG.md, but there is no CHANGELOG.md file in this package directory. If the intention is “every package keeps its own CHANGELOG.md” (per CONTRIBUTING), add it here so it’s included in publishes.

  "files": [
    "build/",
    "src/",
    "./LICENSE",
    "./SECURITY.md",
    "./CHANGELOG.md"
  ],

packages/joint-vitest-plugin-mock-svg/package.json:47

• files now includes ./CHANGELOG.md, but this package doesn’t currently have a CHANGELOG.md file, so it won’t be published. Add the file (even an initial placeholder) or drop it from files until it exists.

  "files": [
    "dist/",
    "mocks/",
    "./LICENSE",
    "./README.md",
    "./SECURITY.md",
    "./CHANGELOG.md"
  ],

.changeset/clear-maps-begin.md:6

• This “empty changeset” file contains trailing whitespace/blank body content. Keeping it to the minimal empty-changeset form avoids accidental non-empty summaries and reduces noisy diffs.

---

---


  

CLAUDE.md:47

• The Jest CLI flag in this example uses --testPathPatterns, which isn’t a valid Jest option (Jest uses --testPathPattern). As written, copying this command will fail.

For joint-react Jest tests:
```bash
cd packages/joint-react
yarn jest --testPathPatterns="ComponentName"

</details>