open-nomad/contributing/CHANGELOG.md
Mahmood Ali 94913d2ad6
Adopt go-changelog in Nomad (#10825)
Adopts [`go-changelog`](https://github.com/hashicorp/go-changelog) for managing Nomad's changelog. `go-changelog` is becoming the HashiCorp defacto standard tool for managing changelog, e.g. [Consul](https://github.com/hashicorp/consul/pull/8387), [Vault](https://github.com/hashicorp/vault/pull/10363), [Waypoint](https://github.com/hashicorp/waypoint/pull/1179). [Consul](https://github.com/hashicorp/consul/pull/8387) seems to be the first product to adopt it, and its PR has the most context - though I've updated `.changelog/README.md` with the relevant info here.

## Changes to developers workflow

When opening PRs, developers should add a changelog entry in `.changelog/<PR#>.txt`. Check [`.changelog/README.md`](https://github.com/hashicorp/nomad/blob/docs-adopt-gochangelog/.changelog/README.md#developer-guide). 

For the WIP release, entries can be amended even after the PR merged, and new files may be added post-hoc (e.g. during transition period, missed accidentally, community PRs, etc).

### Transitioning

Pending PRs can start including the changelog entry files immediately.

For 1.1.3/1.0.9 cycle, the release coordinator should create the entries for any PR that gets merged without a changelog entry file. They should also move any 1.1.3 entry in CHANGELOG.md to a changelog entry file, as this PR done for GH-10818.

## Changes to release process

Before cutting a release, release coordinator should update the changelog by inserting the output of `make changelog` to CHANGELOG.md with appropriate headers. See [`.changelog/README.md`](https://github.com/hashicorp/nomad/blob/docs-adopt-gochangelog/.changelog/README.md#how-to-generate-changelog-entries-for-release) for more details.


## Details

go-changelog is a basic templating engine for maintaining changelog in HashiCorp environment.

It expects the changelog entries as files indexed by their PR number. The CLI generates the changelog section for a release by comparing two git references (e.g. `HEAD` and the latest release, e.g. `v1.1.2`), and still requires manual process for updating CHANGELOG.md and final formatting.

The approach has many nice advantages:
* Avoids changelog related merge conflicts: Each PR touches different file!
* Copes with amendments and post-PR updates: Just add or update a changelog entry file using the original PR numbers.
* Addresses the release backporting scenario: Cherry-picking PRs will cherry-pick the relevant changelog entry automatically!
* Only relies on data available through `git` - no reliance on GitHub metadata or require GitHub credentials

The approach has few downsides though:
* CHANGELOG.md going stale during development and must be updated manually before cutting the release
  * Repository watchers can no longer glance at the CHANGELOG.md to see upcoming changes
  * We can periodically update the file, but `go-changelog` tool does not aid with that
* `go-changelog` tool does not offer good error reporting. If an entry is has an invalid tag (e.g. uses `release-note:bugfix` instead of `release-note:bug`), the entry will be dropped silently
  * We should update go-changelog to warn against unexpected entry tags
  * TODO: Meanwhile, PR reviewers and release coordinators should watch out

## Potential follow ups

We should follow up with CI checks to ensure PR changes include a warning. I've opted not to include that now. We still make many non-changelog-worth PRs for website/docs, for large features that get merged in multiple small PRs. I did not want to include a check that fails often.

Also, we should follow up to have `go-changelog` emit better warnings on unexpected tag.
2021-07-06 10:46:53 -04:00

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# How To Use
Nomad uses [`go-changelog`](https://github.com/hashicorp/go-changelog) to generate its changelog on release.
To install, run the following command:
```
go install github.com/hashicorp/go-changelog/cmd/changelog-build@latest
```
## Developer Guide
PRs with code changes should include a `.changelog/<PR Number>.txt` file highlighting the user visible change.
The changelog entry should include the affected component (e.g. `driver/docker`, `api`), and a user-centric summary of the change. If an issue warrants more elaborate description, also update the [Upgrade Guide](../website/content/docs/upgrade/upgrade-specific.mdx).
Use the PR number as the file name. Enterprise private changes should have an entry in the OSS repository referencing a public GitHub issues detailing the change and impact.
The `.txt` files have a markdown-like syntax, with a tag signifying the entry type.
Below are some examples of how to generate a CHANGELOG entry with your pull request.
### Improvement
~~~
```release-note:improvement
internal/server: Add new option for configs
```
~~~
### Feature
Significant major release features. Typically included in release blog announcement and keynotes.
~~~
```release-note:feature
**Consul namespace support (Enterprise)**: Run Nomad-defined services in their HashiCorp Consul namespaces more easily using Nomad Enterpris
```
~~~
### Improvements
Improvements are incremental and quality of life enhancement that don't rise to the FEATURES level:
```release-note:improvement
cli: Added `-monitor` flag to `deployment status` command and automatically monitor deployments from `job run` command.
```
### Bug
~~~
```release-note:bug
client/fingerprint/java: Fixed a bug where java fingerprinter would not detect some Java distributions
```
~~~
### Multiple Entries
If a PR has multiple entries,
~~~
```release-note:bug
driver/docker: Fix broken code
```
```release-note:bug
client: Fix broken code
```
```release-note:bug
cli: Fix broken code
```
~~~
### Long Description with Markdown
~~~
```release-note:feature
main: Lorem ipsum dolor `sit amet`, _consectetur_ adipiscing elit, **sed** do
eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim
veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
```
~~~
## How to generate CHANGELOG entries for release
Below is an example for running `go-changelog` to generate a collection of
entries. It will generate output that can be inserted into CHANGELOG.md manually.
To generate latest release changelog entry:
```
make changelog
```
You can also call `changelog-build` binary directly. For more information as to what each flag does, make sure to run `changelog-build -help`.
```
cd .changelog
changelog-build -last-release v1.1.2 -this-release HEAD \
-entries-dir . -changelog-template changelog.tmpl -note-template note.tmpl
```
The command will output the changelog entries to be inserted into CHANGELOG.md with version header (e.g. `## 1.1.3 (August 10, 2022)`). The output is like:
```md
IMPROVEMENTS:
* Added the `bar` interface. [[GH-2032](https://github.com/hashicorp/nomad/issues/2032)]
DEPRECATIONS:
* Deprecated the `foo` interface, please use the `bar` interface instead. [[GH-1001](https://github.com/hashicorp/nomad/issues/1001)]
BUG FIXES:
* csi: fixed a CLI panic when formatting `volume status` with `-verbose` flag [[GH-10818](https://github.com/hashicorp/nomad/issues/10818)]
```
## FAQ
### Can I amend the changelog entry after the PR merged?
Yes. If the release is not out, just update the entry file, or add missed entries. If the original PR is a to-be-backported change, ensure the changelog entry update PR also has the `label:stage/needs-backporting` and appropriate milestone so the backport includes the update too.
When amending entries for an already published release, update the CHANGELOG.md file directly.
### Just modified the entry file, but the `go-changelog` isn't picking it up.
Commit the entry first! `go-changelog` operators on committed files only.