chore: use a gitflow-like workflow for the project (#4416)

* chore: use a gitflow-like workflow for the project

* Update .github/CONTRIBUTING.md

Co-Authored-By: Natalia Tepluhina <NataliaTepluhina@users.noreply.github.com>

Author: haoqunjiang

.github/COMMIT_CONVENTION.md

@@ -56,6 +56,8 @@ A commit message consists of a **header**, **body** and **footer**.  The header
 
 The **header** is mandatory and the **scope** of the header is optional.
 
+A `!` MAY be appended prior to the `:` in the type/scope prefix, to further draw attention to breaking changes. `BREAKING CHANGE:` description MUST also be included in the body or footer, along with the `!` in the prefix.
+
 ### Revert
 
 If the commit reverts a previous commit, it should begin with `revert: `, followed by the header of the reverted commit. In the body it should say: `This reverts commit <hash>.`, where the hash is the SHA of the commit being reverted.

.github/CONTRIBUTING.md

@@ -1,3 +1,17 @@
+## Workflow
+
+The Git workflow used in this project is largely inspired by [Gitflow workflow](https://www.atlassian.com/git/tutorials/comparing-workflows/gitflow-workflow).
+
+There are two main branches: `master` and `next`, corresponding to the npm `dist-tag`s with the same names.
+The documentation website for the current CLI version <https://cli.vuejs.org> is deployed from the `master` branch, while documentation for new features <https://next.cli.vuejs.org/> is deployed from `next` branch.
+
+When sending documentation pull requests, please fork your branches from these two branches.
+
+The development branch is `dev`.
+And there are several version branches for archiving old versions of Vue CLI, such as `v2`, `v3`.
+
+Pull requests that touches the code should be forked from `dev`, unless it's only targeting an old version.
+
 ## Development Setup
 
 This project uses a monorepo setup that requires using [Yarn](https://yarnpkg.com) because it relies on [Yarn workspaces](https://yarnpkg.com/blog/2017/08/02/introducing-workspaces/).

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,27 @@
+<!-- Please don't delete this template -->
+
+<!-- PULL REQUEST TEMPLATE -->
+<!-- (Update "[ ]" to "[x]" to check a box) -->
+
+**What kind of change does this PR introduce?** (check at least one)
+
+- [ ] Bugfix
+- [ ] Feature
+- [ ] Code style update
+- [ ] Refactor
+- [ ] Docs
+- [ ] Underlying tools
+- [ ] Other, please describe:
+
+<!--
+Note:
+When submitting documentation PRs, please target the `master` branch (https://cli.vuejs.org) or `next` branch (https://next.cli.vuejs.org)
+When submitting coding PRs, please target the `dev` branch.
+-->
+
+**Does this PR introduce a breaking change?** (check one)
+
+- [ ] Yes
+- [ ] No
+
+**Other information:**