Document installation via install.sh script

INSTALL.md

@@ -16,7 +16,7 @@ To update:
 $ brew upgrade doppler
 ```
 
-Alternatively, you can download the doppler `pkg` file from the [Releases](https://github.com/DopplerHQ/cli/releases/latest) page. This will install the doppler binary in `/usr/local/bin`. Note that this installation method does not support seamless updates. To update, you'll need to download and run the new `pkg` file.
+Alternatively, you can install the CLI via [shell script](#linuxmacosbsd-shell-script), or via the doppler `.pkg` file on the [Releases](https://github.com/DopplerHQ/cli/releases/latest) page. These methods will install the doppler binary directly to `/usr/local/bin` and do not support seamless updates. To update, you'll need to re-run the installation.
 
 ## Windows
 
@@ -77,6 +77,20 @@ To update:
 $ sudo yum update doppler
 ```
 
+## Linux/macOS/BSD shell script
+
+You can bypass package managers and quickly install the latest version of the CLI via shell script. The script automatically downloads and installs the CLI binary most appropriate for your system's architecture. It is also fully POSIX compliant to support all linux and bsd variants with minimal dependencies.
+
+Note that this installation method is only recommended for ephemeral environments like CI jobs. Longer-lived environments that expect to receive updates should install the CLI via a package manager.
+
+```sh
+curl -LO https://cli.doppler.com/install.sh || wget https://cli.doppler.com/install.sh
+chmod +x install.sh
+sudo ./install.sh
+```
+
+You can find the source `install.sh` file in this repo's `scripts` directory.
+
 ## Docker
 
 We currently publish these Docker tags:

README.md

@@ -10,7 +10,7 @@ The Doppler CLI is the official tool for interacting with your Enclave secrets a
 
 ## Install
 
-The Doppler CLI is available in several popular package managers. It's also [available](https://github.com/DopplerHQ/cli/releases/latest) as a standalone binary.
+The Doppler CLI is available in several popular package managers. It can also be installed via [shell script](https://github.com/DopplerHQ/cli/blob/master/INSTALL.md#linuxmacosbsd-shell-script), and downloaded as a [standalone binary](https://github.com/DopplerHQ/cli/releases/latest).
 
 For more info, including instructions on verifying binary signatures, see the [Install](INSTALL.md) page.
 
@@ -67,7 +67,8 @@ Once installed, setup should only take a minute. You'll authorize the CLI to acc
 ```sh
 $ doppler login                     # generate auth credentials
 $ doppler enclave setup             # select your project and config
-$ doppler configure --all           # (optional) view local configuration
+# optional
+$ doppler configure --all           # view local configuration
 ```
 
 By default, `doppler login` scopes the generated token globally (`--scope=*`). This means that the token will be accessible to your projects in any local directory. To limit the scope of the token, specify the `scope` flag during login: `doppler login --scope=.`.