docs: Give working advice on how to get the tree and dependencies.

README.md

@@ -19,8 +19,27 @@ Scuttlebutt, as well as a platform for writing and running web applications.
 Builds on Linux (x86_64 and aarch64), MacOS, OpenBSD, and Haiku. Builds for
 all of those host platforms plus mingw64, iOS, and android.
 
-1. Requires openssl (`libssl-dev`, in debian-speak). All other dependencies
-   are kept up to date in the tree.
+Tilde Friends uses git submodules, so either:
+
+```
+git clone --recurse-submodules https://dev.tildefriends.net/cory/tildefriends.git
+```
+
+or:
+
+```
+git clone https://dev.tildefriends.net/cory/tildefriends.git
+cd tildefriends
+git submodule update --init --recursive
+```
+
+The `.tar.xz` releases are all-inclusive.
+
+The gitea `Source Code (ZIP)` and `Source Code (TAR.GZ)` are missing
+dependencies, so don't use those.
+
+1. On Linux only, system OpenSSL libraries (`libssl-dev`, in debian-speak) is
+   assumed to be available.
 2. To build, run `make debug` or `make release`. An executable will be
    generated in a subdirectory of `out/`.
 3. It's possible to build for Android, iOS, and Windows on Linux, if you have