chore: report docker upgrade command correctly (#2745)

Dockerfile

@@ -6,4 +6,5 @@ RUN apk --no-cache add git curl
 RUN echo "optic-docker" > /etc/machine-id
 RUN set -e; sh -c "$(curl -s --location https://install.useoptic.com/install.sh)" -- $OPTIC_CLI_VERSION /usr/local/bin
 
+ENV INSTALLATION_METHOD="docker"
 ENTRYPOINT ["/usr/local/bin/optic"]

projects/optic/src/init.ts

@@ -35,17 +35,30 @@ import path from 'path';
 
 const packageJson = require('../package.json');
 
-function getInstallMethod(): 'binary' | 'npm/yarn' {
-  return process.env.INSTALLATION_METHOD === 'binary' ? 'binary' : 'npm/yarn';
+type installMethod = 'binary' | 'npm/yarn' | 'docker';
+const allowedMethods = ['binary', 'npm/yarn', 'docker'];
+function getInstallMethod(): installMethod {
+  if (
+    process.env.INSTALLATION_METHOD !== undefined &&
+    allowedMethods.includes(process.env.INSTALLATION_METHOD)
+  ) {
+    return process.env.INSTALLATION_METHOD as installMethod;
+  }
+
+  return 'npm/yarn';
 }
 
 const getInstallInstruction = (): string => {
-  if (getInstallMethod() === 'binary') {
-    const binDir = path.dirname(process.execPath);
-    return `sh -c "$(curl -s --location https://install.useoptic.com/install.sh)" -- latest ${binDir}`;
-  } else {
-    return 'npm i -g @useoptic/optic';
+  const installMethod = getInstallMethod();
+
+  // TODO: distinguish between 'binary' and 'npm/yarn' installations
+  // vercel/pkg is deprecated. waiting on node's native packaging to explore this more
+
+  if (installMethod === 'docker') {
+    return 'docker pull docker.io/useoptic/optic:latest';
   }
+
+  return 'npm i -g @useoptic/optic';
 };
 
 export const initCli = async (