Edit docs/faq.md: add an entry for the just

It is based on the existing explanation of the just on docs/maintenance-upgrading-services.md.

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

docs/faq.md

@@ -80,6 +80,14 @@ Alternatively, you can download Ansible and the playbook itself directly on the
 
 To learn more, see our [dedicated Ansible documentation page](ansible.md).
 
+### What is `just`?
+
+[`just`](https://github.com/casey/just) is a modern command-runner alternative to `make`. It can be used to invoke `ansible-playbook` commands with less typing.
+
+The `just` utility executes shortcut commands (called as "recipes"), which ultimately run `ansible-galaxy` or [`agru`](https://github.com/etkecc/agru) (depending on what is available in your system). The targets of the recipes are defined in [`justfile`](../justfile). It defines commands, most of which are not available on our `Makefile`.
+
+For details about `just` commands, take a look at: [Running `just` commands](just.md).
+
 ### Why use this playbook and not install Synapse and other things manually?
 
 There are various guides telling you how easy it is to install [Synapse](https://github.com/element-hq/synapse).

docs/maintenance-upgrading-services.md

@@ -23,8 +23,6 @@ If it looks good to you, go to the `matrix-docker-ansible-deploy` directory, the
   - either: `just update`
   - or: a combination of `git pull` and `just roles` (or `make roles` if you have `make` program on your computer instead of `just`)
 
-  `just update` and `just roles` are shortcuts (their targets are defined in [`justfile`](../justfile) and executed by the [`just`](https://github.com/casey/just) utility) which ultimately run [agru](https://github.com/etkecc/agru) or [ansible-galaxy](https://docs.ansible.com/ansible/latest/cli/ansible-galaxy.html) (depending on what is available in your system) to download Ansible roles, after upgrading the playbook (in case of `just update`).
-
   If you don't have either `just` tool or `make` program, you can run the `ansible-galaxy` tool directly: `rm -rf roles/galaxy; ansible-galaxy install -r requirements.yml -p roles/galaxy/ --force`
 
 - re-run the [playbook setup](installing.md#maintaining-your-setup-in-the-future) and restart all services: