Provide project source metadata from local git information

[jromero]

Description

As a buildpacks user, I'd like to have the source and version information of my project embedded as metadata in the final app image.

Proposed solution

Based on the spec, we should be able to provide <layers>/project-metadata.toml in this format which would be translated into the io.buildpacks.project.metadata label on the image.

This issue should be scoped to local git information.

Acceptance Criteria

General case

Given I clone a project from git@github.com:buildpacks/pack.git
And `git rev-parse HEAD` returns "8348484564e6aa0699de0ee78c258e88240eb0b5"
And `git describe --tags --always` returns "v0.18.1-2-g83484845"
And `git branch --show-current` returns "main"
And `git remote -v | grep "fetch"` returns:
    "origin	git@github.com:buildpacks/pack.git (fetch)"
And I run `pack build my-app`
When I run the following command `docker inspect my-app | jq -r '.[0].Config.Labels["io.buildpacks.project.metadata"] | fromjson'`
Then I should see:
{
  "type": "git",
  "version": { "commit": "8348484564e6aa0699de0ee78c258e88240eb0b5", "describe": "v0.18.1-2-g83484845"},
  "metadata": {
    "refs": ["main"],
    "url": "git@github.com:buildpacks/pack.git"
  }
}

At a tag(s)

Given I clone a project from git@github.com:buildpacks/pack.git
And `git rev-parse HEAD` returns "8348484564e6aa0699de0ee78c258e88240eb0b5"
And `git describe --tags --always` returns "v0.18.1"
And `git branch --show-current` returns "main"
And `git tag --points-at HEAD` returns:
  v0.18.1
  v0.18.1-rc2
And `git remote -v | grep "fetch"` returns:
    "origin	git@github.com:buildpacks/pack.git (fetch)"
And I run `pack build my-app`
When I run the following command `docker inspect my-app | jq -r '.[0].Config.Labels["io.buildpacks.project.metadata"] | fromjson'`
Then I should see:
{
  "type": "git",
  "version": { "commit": "8348484564e6aa0699de0ee78c258e88240eb0b5", "describe": "v0.18.1"},
  "metadata": {
    "refs": ["main", "v0.18.1", "v0.18.1-rc2"],
    "url": "git@github.com:buildpacks/pack.git"
  }
}

Additional context

This issue is part of an epic of work. The related issues may be see by filtering on epic/source-metadata.

[imnitishng]

I see this is listed in the next milestone, and has already been worked on by someone else. I'd be happy to finish this 😄