Sometimes (in enterprise situations for example) you need to deploy a
1. Custom made extension (that isn't in the store)
2. Regular extension, but you don't have access to the internet 

This is what this project is about, it allows to deploy any extension by:
1. Building the project
2. Under the binary folder create another folder called files
3. Place on a computer with a fixed name, say "ChromeLocalStore"
4. Build a CRX (https://developer.chrome.com/extensions/packaging), either custom or extract one from the official store. Make sure update url points to "ChromeLocalStore" i.e. "update_url": "http://ChromeLocalStore" in the manifest.json.
3. Place any CRX under it with the file name being its ID (for example Chrome Docs Offline ID is ghbmnnjooekpmoecnnnilnnbdlolhkhi so the file name would be ghbmnnjooekpmoecnnnilnnbdlolhkhi.crx)
4. Setup a GPO according to https://www.chromium.org/administrators/policy-list-3#ExtensionInstallForcelist - make sure to write <id>;http://ChromeLocalStore
5. Make sure GPO was updated (gpupdate /force) and start chrome.