Update README (#2)

Author: trevor-e

README.md

@@ -1,25 +1,94 @@
 # Emerge CLI
 
-WIP - starting with just uploading of BYOSnapshots/apps
+The official CLI for Emerge Tools.
 
-## Running
+[Emerge](https://emergetools.com) offers a suite of products to help optimize app size, performance, and quality by detecting regressions before they make it to production. This plugin provides a set of actions to interact with the Emerge API.
 
-View all commands: `ruby emgcli.rb --help`
+## Installation
 
-### Upload snapshots:
+This tool is packaged as a Ruby Gem which can be installed by:
 
-Set the `EMERGE_API_KEY` environment variable to your API key. (alternatively pass with the `--api-token` option)
+```
+gem install emerge
+```
+
+## API Key
+
+Follow our guide to obtain an [API key](https://docs.emergetools.com/docs/uploading-basics#obtain-an-api-key) for your organization. The API Token is used by the CLI to authenticate with the Emerge API. The CLI will automatically pick up the API key if configured as an `EMERGE_API_TOKEN` environment variable, or you can manually pass it into individual commands.
+
+## Snapshots
+
+Uploads a directory of images to be used in [Emerge Snapshot Testing](https://docs.emergetools.com/docs/snapshot-testing).
 
-#### Using with swift-snapshot-testing
+Run `emerge upload snapshots -h` for a full list of supported options.
+
+Example:
 
 ```shell
-bundle exec ruby bin/emerge_cli.rb upload snapshots --name "Awesome App Snapshots" --id "com.awesomeapp" --repo-name "EmergeTools/AwesomeApp" --client-library swift-snapshot-testing --project-root /my/ios/repo
+emerge upload snapshots \
+  --name "AwesomeApp" \
+  --id "com.emerge.awesomeapp" \
+  --repo-name "EmergeTools/AwesomeApp" \
+  path/to/snapshot/images
+```
+
+### Git Configuration
+
+For CI diffs to work, Emerge needs the appropriate Git `sha` and `base_sha` values set on each build. Emerge will automatically compare a build at `sha` against the build we find matching the `base_sha` for a given application id. We also recommend setting `pr_number`, `branch`, and `repo_name` for the best experience.
+
+For example:
+
+- `sha`: `pr-branch-commit-1`
+- `base_sha`: `main-branch-commit-1`
+- `pr_number`: `42`
+- `branch`: `my-awesome-feature`
+- `repo_name`: `EmergeTools/hackernews`
+
+Will compare the snapshot diffs of your pull request changes.
+
+This plugin will automatically configure Git values for you assuming certain Github workflow triggers:
+
+```yaml
+on:
+  # Produce base builds with a 'sha' when commits are pushed to the main branch
+  push:
+    branches: [main]
+
+  # Produce branch comparison builds with `sha` and `base_sha` when commits are pushed
+  # to open pull requests
+  pull_request:
+    branches: [main]
+  ...
 ```
 
-#### Using with manual image paths
+If this doesn't cover your use-case, manually set the `sha` and `base_sha` values when calling the Emerge plugin.
+
+### Using with swift-snapshot-testing
+
+Snapshots generated via [swift-snapshot-testing](https://github.com/pointfreeco/swift-snapshot-testing) are natively supported by the CLI by setting `--client-library swift-snapshot-testing` and a `--project-root` directory. This will scan your project for all images found in `__Snapshot__` directories.
+
+Example:
 
 ```shell
-bundle exec ruby bin/emerge_cli.rb upload snapshots /your/snapshots/path1 /your/snapshots/path2 --name "Awesome App Snapshots" --id "com.awesomeapp" --repo-name "EmergeTools/AwesomeApp"
+emerge upload snapshots \
+  --name "AwesomeApp swift-snapshot-testing" \
+  --id "com.emerge.awesomeapp.swift-snapshot-testing" \
+  --repo-name "EmergeTools/AwesomeApp" \
+  --client-library swift-snapshot-testing \
+  --project-root /my/awesomeapp/ios/repo
 ```
 
-Git info will be set automatically.
+### Using with Paparazzi
+
+Snapshots generated via [Paparazzi](https://github.com/cashapp/paparazzi) are natively supported by the CLI by setting `--client-library paparazzi` and a `--project-root` directory. This will scan your project for all images found in `src/test/snapshots/images` directories.
+
+Example:
+
+```shell
+emerge upload snapshots \
+  --name "AwesomeApp Paparazzi" \
+  --id "com.emerge.awesomeapp.paparazzi" \
+  --repo-name "EmergeTools/AwesomeApp" \
+  --client-library paparazzi \
+  --project-root /my/awesomeapp/android/repo
+```