add ctags installation instructions to readme

Author: msukkari

README.md

@@ -130,12 +130,16 @@ Sourcebot also supports indexing GitLab & BitBucket. Checkout the [index.json](.
 
 1. Install <a href="https://go.dev/doc/install"><img src="https://go.dev/favicon.ico" width="16" height="16"> go</a> and <a href="https://nodejs.org/"><img src="https://nodejs.org/favicon.ico" width="16" height="16"> NodeJS</a>. Note that a NodeJS version of at least `21.1.0` is required.
 
-2. Clone the repository with submodules:
+2. Install ctags (required by zoekt-indexserver):
+   Mac: `brew install universal-ctags`
+   Ubuntu: `apt-get install universal-ctags`
+
+3. Clone the repository with submodules:
     ```sh
     git clone --recurse-submodules https://github.com/TaqlaAI/sourcebot.git
     ```
 
-3. Run make to build zoekt and install dependencies:
+4. Run make to build zoekt and install dependencies:
     ```sh
     cd sourcebot
     make

package.json

@@ -5,7 +5,7 @@
   "scripts": {
     "dev": "npm-run-all --print-label --parallel next:dev zoekt:webserver zoekt:indexserver",
     "zoekt:webserver": "export PATH=\"$(PWD)/bin:$PATH\" && zoekt-webserver -index .sourcebot/index -rpc",
-    "zoekt:indexserver": "export PATH=\"$(PWD)/bin:$PATH\" && zoekt-indexserver -data_dir .sourcebot -mirror_config config.json",
+    "zoekt:indexserver": "export PATH=\"$(PWD)/bin:$PATH\" && export CTAGS_COMMAND=ctags && zoekt-indexserver -data_dir .sourcebot -mirror_config config.json",
     "next:dev": "next dev",
     "build": "next build",
     "start": "next start",