docs: branch selection (#154)

Author: mtojek

README.md

@@ -24,7 +24,7 @@ Build development environments from a Dockerfile on Docker, Kubernetes, and Open
 
 The easiest way to get started is to run the `envbuilder` Docker container that clones a repository, builds the image from a Dockerfile, and runs the `$INIT_SCRIPT` in the freshly built container.
 
-> `/tmp/envbuilder` is used to persist data between commands for the purpose of this demo. You can change it to any directory you want.
+> `/tmp/envbuilder` directory persists demo data between commands. You can choose a different directory.
 
 ```bash
 docker run -it --rm \
@@ -47,6 +47,14 @@ $ vim .devcontainer/Dockerfile
 
 Exit the container, and re-run the `docker run` command... after the build completes, `htop` should exist in the container! 🥳
 
+### Git Branch Selection
+
+Choose a branch using `GIT_URL` with a _ref/heads_ reference. For instance:
+
+```
+GIT_URL=https://github.com/coder/envbuilder-starter-devcontainer/#refs/heads/my-feature-branch
+```
+
 ## Container Registry Authentication
 
 envbuilder uses Kaniko to build containers. You should [follow their instructions](https://github.com/GoogleContainerTools/kaniko#pushing-to-different-registries) to create an authentication configuration.
@@ -85,7 +93,7 @@ resource "kubernetes_deployment" "example" {
   }
   spec {
     spec {
-      container {  
+      container {
         # Define the volumeMount with the pull credentials
         volume_mount {
           name       = "docker-config-volume"
@@ -194,8 +202,7 @@ A sample script to pre-fetch a number of images can be viewed [here](./examples/
 
 The `SETUP_SCRIPT` environment variable dynamically configures the user and init command (PID 1) after the container build process.
 
-> **Note**
-> `TARGET_USER` is passed to the setup script to specify who will execute `INIT_COMMAND` (e.g., `code`).
+> **Note** > `TARGET_USER` is passed to the setup script to specify who will execute `INIT_COMMAND` (e.g., `code`).
 
 Write the following to `$ENVBUILDER_ENV` to shape the container's init process:
 
@@ -225,7 +232,6 @@ docker run -it --rm \
 - [`SSL_CERT_DIR`](https://go.dev/src/crypto/x509/root_unix.go#L25): Identifies which directory to check for SSL certificate files.
 - `SSL_CERT_BASE64`: Specifies a base64-encoded SSL certificate that will be added to the global certificate pool on start.
 
-
 # Local Development
 
 Building `envbuilder` currently **requires** a Linux system.
@@ -243,4 +249,4 @@ On MacOS or Windows systems, we recommend either using a VM or the provided `.de
 - `build`: builds and tags `envbuilder:latest` for your current architecture.
 - `develop`: runs `envbuilder:latest` against a sample Git repository.
 - `test`: run tests.
-- `test-registry`: stands up a local registry for caching images used in tests.
+- `test-registry`: stands up a local registry for caching images used in tests.