docs/tutorial: update custom module tutorial with cue mod registry

Now that we have an append-only version of cue mod registry, we should
switch to recommending that as the default. Which has the added benefit
of meaning that we can drop a pre-requisite.

However for those more familiar/comfortable with existing
container-based setups, we still recommend docker, and in the spirit of
https://cuelang.org/cl/1177163, we add mention of podman. It might be
that with time we push such "detail" to another document, but for now
it's fine in the modules tutorial.

Preview-Path: /docs/tutorial/working-with-a-custom-module-registry
Signed-off-by: Paul Jolly <paul@myitcv.io>
Change-Id: I04de4d35515fa7f4cced881cd70ebe065ffc7093
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cuelang.org/+/1177164
Reviewed-by: Roger Peppe <rogpeppe@gmail.com>
TryBot-Result: CUEcueckoo <cueckoo@gmail.com>

content/docs/tutorial/working-with-a-custom-module-registry/en.md

@@ -42,8 +42,6 @@ This tutorial describes an experimental feature. All details are subject to chan
 - **A command terminal**. `cue` works on all platforms, so any terminal on Linux
   or macOS, and on PowerShell, `cmd.exe` or
   [WSL](https://learn.microsoft.com/en-us/windows/wsl/install) in Windows.
-- **The docker command** or an Open Container Initiative ("OCI") registry that
-  you can write to.
 - **An installed `cue` binary**
   ([installation details]({{< relref "/docs/introduction/installation" >}}))
 - **Some awareness of CUE schemata**
@@ -152,17 +150,31 @@ it represents the schema of the configuration data expected by `FrostyApp`.
 {{{with step}}}
 
 If you do not have access to an OCI registry, start one locally:
+
 {{{with script "en" "start-registry"}}}
 #norun
 
-docker run -p 5000:5000 registry
+cue mod registry localhost:5000
 {{{end}}}
 
+`cue mod registry` is a very simple in-memory OCI server.
+
 CUE should work with all OCI-compatible artifact registries, such as
 the [Google Artifact Registry](https://cloud.google.com/artifact-registry),
-as CUE uses the standard OCI protocols spoken by such registries.
+as CUE uses the standard OCI protocols spoken by such registries. For example,
+here are some alternatives:
+
+{{{with script "en" "start-registry alternatives"}}}
+#norun
+
+# running a local registry via docker
+docker run -p 5000:5000 registry
+
+# running a local registry via podman
+podman run -p 5000:5000 registry
+{{{end}}}
 
-In our example we will run a local instance of the docker registry on port 5000.
+In our example we will run a local instance of the in-memory registry on port 5000.
 If you need to run one locally, invoke the above `docker` command in a separate
 terminal so the registry remains running while you follow the rest of this
 tutorial.

hugo/content/en/docs/tutorial/working-with-a-custom-module-registry/index.md

@@ -35,8 +35,6 @@ This tutorial describes an experimental feature. All details are subject to chan
 - **A command terminal**. `cue` works on all platforms, so any terminal on Linux
   or macOS, and on PowerShell, `cmd.exe` or
   [WSL](https://learn.microsoft.com/en-us/windows/wsl/install) in Windows.
-- **The docker command** or an Open Container Initiative ("OCI") registry that
-  you can write to.
 - **An installed `cue` binary**
   ([installation details]({{< relref "/docs/introduction/installation" >}}))
 - **Some awareness of CUE schemata**
@@ -145,15 +143,27 @@ it represents the schema of the configuration data expected by `FrostyApp`.
 {{< step stepNumber="4" >}}
 
 If you do not have access to an OCI registry, start one locally:
-```text { title="TERMINAL" codeToCopy="ZG9ja2VyIHJ1biAtcCA1MDAwOjUwMDAgcmVnaXN0cnkK" }
-$ docker run -p 5000:5000 registry
+
+```text { title="TERMINAL" codeToCopy="Y3VlIG1vZCByZWdpc3RyeSBsb2NhbGhvc3Q6NTAwMAo=" }
+$ cue mod registry localhost:5000
 ```
 
+`cue mod registry` is a very simple in-memory OCI server.
+
 CUE should work with all OCI-compatible artifact registries, such as
 the [Google Artifact Registry](https://cloud.google.com/artifact-registry),
-as CUE uses the standard OCI protocols spoken by such registries.
+as CUE uses the standard OCI protocols spoken by such registries. For example,
+here are some alternatives:
+
+```text { title="TERMINAL" codeToCopy="ZG9ja2VyIHJ1biAtcCA1MDAwOjUwMDAgcmVnaXN0cnkKcG9kbWFuIHJ1biAtcCA1MDAwOjUwMDAgcmVnaXN0cnkK" }
+# running a local registry via docker
+$ docker run -p 5000:5000 registry
+
+# running a local registry via podman
+$ podman run -p 5000:5000 registry
+```
 
-In our example we will run a local instance of the docker registry on port 5000.
+In our example we will run a local instance of the in-memory registry on port 5000.
 If you need to run one locally, invoke the above `docker` command in a separate
 terminal so the registry remains running while you follow the rest of this
 tutorial.