Adds contributing guide

Author: cyriltovena

docs/internal/README.md

@@ -0,0 +1,94 @@
+# Contributing
+
+Welcome! We're excited that you're interested in contributing. Below are some basic guidelines.
+
+## Workflow
+
+Grafana Phlare follows a standard GitHub pull request workflow. If you're unfamiliar with this workflow, read the very helpful [Understanding the GitHub flow](https://guides.github.com/introduction/flow/) guide from GitHub.
+
+You are welcome to create draft PRs at any stage of readiness - this
+can be helpful to ask for assistance or to develop an idea. But before
+a piece of work is finished it should:
+
+- Be organised into one or more commits, each of which has a commit message that describes all changes made in that commit ('why' more than 'what' - we can read the diffs to see the code that changed).
+- Each commit should build towards the whole - don't leave in back-tracks and mistakes that you later corrected.
+- Have unit for new functionality or tests that would have caught the bug being fixed.
+- If you have made any changes to flags, configs and/or protobuf definitions, run `make generate` and commit the changed files.
+
+## Requirement
+
+To be able to run make targets you'll need to install:
+
+- [Go](https://go.dev/doc/install) (> 1.18)
+- [Docker](https://docs.docker.com/engine/install/)
+
+All other required tools will be automatically downloaded `$(pwd)/.tmp/bin`.
+
+> If you need a new CLI, we recommend you follow the same pattern and downloads requirement from the makefile.
+
+## Formatting
+
+Grafana Phlare uses [`golang-ci-lint`](https://github.com/golangci/golangci-lint) tool to format the Go files, and sort imports.
+We use goimports with `-local github.com/grafana/phlare` parameter, to put Grafana Mimir internal imports into a separate group. We try to keep imports sorted into three groups: imports from standard library, imports of 3rd party packages and internal Grafana Phlare imports. Goimports will fix the order, but will keep existing newlines between imports in the groups. We try to avoid extra newlines like that.
+
+Use `make lint` to ensure formatting is correct.
+
+## Building Grafana Phlare
+
+To build:
+
+```
+make go/bin
+```
+
+To run the unit tests suite:
+
+```
+make go/test
+```
+
+To build the docker image uses:
+
+```
+make docker-image/phlare/build
+```
+
+This target uses the `go/bin` target to first build binaries to include in the image.
+make sure to pass the correct `GOOS` and `GOARCH` env variables.
+
+For example for `linux/amd64`:
+
+```
+GOOS=linux GOARCH=amd64 make docker-image/phlare/build
+```
+
+### Dependency management
+
+We uses [Go modules](https://golang.org/cmd/go/#hdr-Modules__module_versions__and_more) to manage dependencies on external packages.
+However we don't commit the `vendor/` folder.
+
+To add or update a new dependency, use the `go get` command:
+
+```bash
+# Pick the latest tagged release.
+go get example.com/some/module/pkg
+
+# Pick a specific version.
+go get example.com/some/module/[email protected]
+```
+
+Tidy up the `go.mod` and `go.sum` files:
+
+```bash
+make go/mod
+```
+
+You have to commit the changes to `go.mod` and `go.sum` before submitting the pull request.
+
+## Documentation
+
+The Grafana Phlare documentation is compiled into a website published at [grafana.com](https://grafana.com/).
+
+To start the website locally you can use `make docs/docs` and follow console instructions to access the website.
+
+Note: if you attempt to view pages on Github, it's likely that you might find broken links or pages. That is expected and should not be addressed unless it is causing issues with the site that occur as part of the build.