nixos/doc: Improve documentation of documentation

- Move contents of README.md from
  nixos/modules/installer/tools/manpages/ to
  nixos/doc/manual/contributing-to-this-manual.chapter.md.
- Don't mention DocBook as its obsolete and too specific.
- Rename derivation attribute name of configuration.nix(5) manual page,
  both on the `contributing-to-this-manual.chapter.md`, and in other
  places.

6 files changed, 86 insertions, 70 deletions

diff --git a/nixos/doc/manual/contributing-to-this-manual.chapter.md b/nixos/doc/manual/contributing-to-this-manual.chapter.md
index 4633c7e1b05..b7282d65c41 100644
--- a/nixos/doc/manual/contributing-to-this-manual.chapter.md
+++ b/nixos/doc/manual/contributing-to-this-manual.chapter.md
@@ -6,6 +6,7 @@ You can quickly check your edits with the following:
 
 ```ShellSession
 $ cd /path/to/nixpkgs
+$ $EDITOR doc/nixos/manual/... # edit the manual
 $ nix-build nixos/release.nix -A manual.x86_64-linux
 ```
 
@@ -13,24 +14,96 @@ If the build succeeds, the manual will be in `./result/share/doc/nixos/index.htm
 
 There's also [a convenient development daemon](https://nixos.org/manual/nixpkgs/unstable/#sec-contributing-devmode).
 
-**Contributing to the man pages**
+The above instructions don't deal with the appendix of available `configuration.nix` options, and the manual pages related to NixOS. These are built, and written in a different location and in a different format, as explained in the next sections.
 
-The man pages are written in [DocBook] which is XML.
+## Contributing to the `configuration.nix` options documentation {#sec-contributing-options}
 
-To see what your edits look like:
+The documentation for all the different `configuration.nix` options is automatically generated by reading the `description`s of all the NixOS options defined at `nixos/modules/`. If you want to improve such `description`, find it in the `nixos/modules/` directory, and edit it and open a pull request.
+
+To see how your changes render on the web, run again:
+
+```ShellSession
+$ nix-build nixos/release.nix -A manual.x86_64-linux
+```
+
+And you'll see the changes to the appendix in the path `result/share/doc/nixos/options.html`.
+
+You can also build only the `configuration.nix(5)` manual page, via:
 
 ```ShellSession
 $ cd /path/to/nixpkgs
-$ nix-build nixos/release.nix -A manpages.x86_64-linux
+$ nix-build nixos/release.nix -A nixos-configuration-reference-manpage.x86_64-linux
 ```
 
-You can then read the man page you edited by running
+And observe the result via:
 
 ```ShellSession
-$ man --manpath=result/share/man nixos-rebuild # Replace nixos-rebuild with the command whose manual you edited
+$ man --local-file result/share/man/man5/configuration.nix.5
+```
+
+If you're on a different architecture that's supported by NixOS (check file `nixos/release.nix` on Nixpkgs' repository) then replace `x86_64-linux` with the architecture. `nix-build` will complain otherwise, but should also tell you which architecture you have + the supported ones.
+
+## Contributing to `nixos-*` tools' manpages {#sec-contributing-nixos-tools}
+
+The manual pages for the tools available in the installation image can be found in Nixpkgs' by running (e.g for `nixos-rebuild`):
+
+```ShellSession
+$ git ls | grep nixos-rebuild.8
+```
+
+Man pages are written in [`mdoc(7)` format](https://mandoc.bsd.lv/man/mdoc.7.html) and should be portable between mandoc and groff for rendering (though minor differences may occur, mandoc and groff seem to have slightly different spacing rules.)
+
+For previewing edited files, you can just run `man --local-file path/to/file.8` and you will see it rendered.
+
+Being written in `mdoc`, these manpages use semantic markup. This file provides a guideline on where to apply which of the semantic elements of `mdoc`.
+
+### Command lines and arguments {#ssec-contributing-nixos-tools-cli-and-args}
+
+In any manpage, commands, flags and arguments to the *current* executable should be marked according to their semantics. Commands, flags and arguments passed to *other* executables should not be marked like this and should instead be considered as code examples and marked with `Ql`.
+
+- Use `Fl` to mark flag arguments, `Ar` for their arguments.
+- Repeating arguments should be marked by adding ellipses (`...`).
+- Use `Cm` to mark literal string arguments, e.g. the `boot` command argument passed to `nixos-rebuild`.
+- Optional flags or arguments should be marked with `Op`. This includes optional repeating arguments.
+- Required flags or arguments should not be marked.
+- Mutually exclusive groups of arguments should be enclosed in curly brackets, preferably created with `Bro`/`Brc` blocks.
+
+When an argument is used in an example it should be marked up with `Ar` again to differentiate it from a constant. For example, a command with a `--host name` flag that calls ssh to retrieve the host's local time would signify this thusly:
+```
+This will run
+.Ic ssh Ar name Ic time
+to retrieve the remote time.
 ```
 
-If you're on a different architecture that's supported by NixOS (check nixos/release.nix) then replace `x86_64-linux` with the architecture.
-`nix-build` will complain otherwise, but should also tell you which architecture you have + the supported ones.
+### Paths, NixOS options, environment variables {#ssec-contributing-nixos-tools-options-and-environment}
+
+Constant paths should be marked with `Pa`, NixOS options with `Va`, and environment variables with `Ev`.
+
+Generated paths, e.g. `result/bin/run-hostname-vm` (where `hostname` is a variable or arguments) should be marked as `Ql` inline literals with their variable components marked appropriately.
+
+ - Taking `hostname` from an argument become `.Ql result/bin/run- Ns Ar hostname Ns -vm`
+ - Taking `hostname` from a variable otherwise defined becomes `.Ql result/bin/run- Ns Va hostname Ns -vm`
+
+### Code examples and other commands {#ssec-contributing-nixos-tools-code-examples}
 
-[DocBook]: https://en.wikipedia.org/wiki/DocBook
+In free text names and complete invocations of other commands (e.g. `ssh` or `tar -xvf src.tar`) should be marked with `Ic`, fragments of command lines should be marked with `Ql`.
+
+Larger code blocks or those that cannot be shown inline should use indented literal display block markup for their contents, i.e.
+
+```
+.Bd -literal -offset indent
+...
+.Ed
+```
+
+Contents of code blocks may be marked up further, e.g. if they refer to arguments that will be substituted into them:
+
+```
+.Bd -literal -offset indent
+{
+  options.hostname = "\c
+.Ar hostname Ns \c
+";
+}
+.Ed
+```
diff --git a/nixos/doc/manual/default.nix b/nixos/doc/manual/default.nix
index 962c74edee8..85eab08a457 100644
--- a/nixos/doc/manual/default.nix
+++ b/nixos/doc/manual/default.nix
@@ -185,7 +185,7 @@ in rec {
 
 
   # Generate the configuration.nix manual package
-  configuration-manual = runCommand "nixos-manpages"
+  nixos-configuration-reference-manpage = runCommand "nixos-configuration-reference-manpage"
     { nativeBuildInputs = [
         buildPackages.installShellFiles
         buildPackages.nixos-render-docs
diff --git a/nixos/modules/installer/tools/manpages/README.md b/nixos/modules/installer/tools/manpages/README.md
deleted file mode 100644
index 05cb83902c7..00000000000
--- a/nixos/modules/installer/tools/manpages/README.md
+++ /dev/null
@@ -1,57 +0,0 @@
-# NixOS manpages
-
-This is the collection of NixOS manpages, excluding `configuration.nix(5)`.
-
-Man pages are written in [`mdoc(7)` format](https://mandoc.bsd.lv/man/mdoc.7.html) and should be portable between mandoc and groff for rendering (though minor differences may occur, mandoc and groff seem to have slightly different spacing rules.)
-
-For previewing edited files, you can just run `man -l path/to/file.8` and you will see it rendered.
-
-Being written in `mdoc` these manpages use semantic markup. This file provides a guideline on where to apply which of the semantic elements of `mdoc`.
-
-### Command lines and arguments
-
-In any manpage, commands, flags and arguments to the *current* executable should be marked according to their semantics. Commands, flags and arguments passed to *other* executables should not be marked like this and should instead be considered as code examples and marked with `Ql`.
-
- - Use `Fl` to mark flag arguments, `Ar` for their arguments.
- - Repeating arguments should be marked by adding ellipses (`...`).
- - Use `Cm` to mark literal string arguments, e.g. the `boot` command argument passed to `nixos-rebuild`.
- - Optional flags or arguments should be marked with `Op`. This includes optional repeating arguments.
- - Required flags or arguments should not be marked.
- - Mutually exclusive groups of arguments should be enclosed in curly brackets, preferably created with `Bro`/`Brc` blocks.
-
-When an argument is used in an example it should be marked up with `Ar` again to differentiate it from a constant. For example, a command with a `--host name` flag that calls ssh to retrieve the host's local time would signify this thusly:
-```
-This will run
-.Ic ssh Ar name Ic time
-to retrieve the remote time.
-```
-
-### Paths, NixOS options, environment variables
-
-Constant paths should be marked with `Pa`, NixOS options with `Va`, and environment variables with `Ev`.
-
-Generated paths, e.g. `result/bin/run-hostname-vm` (where `hostname` is a variable or arguments) should be marked as `Ql` inline literals with their variable components marked appropriately.
-
- - Taking `hostname` from an argument become `.Ql result/bin/run- Ns Ar hostname Ns -vm`
- - Taking `hostname` from a variable otherwise defined becomes `.Ql result/bin/run- Ns Va hostname Ns -vm`
-
-### Code examples and other commands
-
-In free text names and complete invocations of other commands (e.g. `ssh` or `tar -xvf src.tar`) should be marked with `Ic`, fragments of command lines should be marked with `Ql`.
-
-Larger code blocks or those that cannot be shown inline should use indented literal display block markup for their contents, i.e.
-```
-.Bd -literal -offset indent
-...
-.Ed
-```
-Contents of code blocks may be marked up further, e.g. if they refer to arguments that will be substituted into them:
-```
-.Bd -literal -offset indent
-{
-  options.hostname = "\c
-.Ar hostname Ns \c
-";
-}
-.Ed
-```
diff --git a/nixos/modules/misc/documentation.nix b/nixos/modules/misc/documentation.nix
index c94f5c53d9c..46462c5abd4 100644
--- a/nixos/modules/misc/documentation.nix
+++ b/nixos/modules/misc/documentation.nix
@@ -346,7 +346,7 @@ in
       system.build.manual = manual;
 
       environment.systemPackages = []
-        ++ optional cfg.man.enable manual.configuration-manual
+        ++ optional cfg.man.enable manual.nixos-configuration-reference-manpage
         ++ optionals cfg.doc.enable [ manual.manualHTML nixos-help ];
     })
 
diff --git a/nixos/release.nix b/nixos/release.nix
index 2d7661e935f..6da6faab73b 100644
--- a/nixos/release.nix
+++ b/nixos/release.nix
@@ -143,7 +143,7 @@ in rec {
   manualHTML = buildFromConfig ({ ... }: { }) (config: config.system.build.manual.manualHTML);
   manual = manualHTML; # TODO(@oxij): remove eventually
   manualEpub = (buildFromConfig ({ ... }: { }) (config: config.system.build.manual.manualEpub));
-  manpages = buildFromConfig ({ ... }: { }) (config: config.system.build.manual.configuration-manual);
+  nixos-configuration-reference-manpage = buildFromConfig ({ ... }: { }) (config: config.system.build.manual.nixos-configuration-reference-manpage);
   options = (buildFromConfig ({ ... }: { }) (config: config.system.build.manual.optionsJSON)).x86_64-linux;
 
 
diff --git a/pkgs/tools/nix/nixos-install-tools/default.nix b/pkgs/tools/nix/nixos-install-tools/default.nix
index 37a3f880536..e0b24a4e70d 100644
--- a/pkgs/tools/nix/nixos-install-tools/default.nix
+++ b/pkgs/tools/nix/nixos-install-tools/default.nix
@@ -20,7 +20,7 @@ in
     inherit (config.system.build)
       nixos-install nixos-generate-config nixos-enter;
 
-    inherit (config.system.build.manual) configuration-manual;
+    inherit (config.system.build.manual) nixos-configuration-reference-manpage;
   };
 
   extraOutputsToInstall = ["man"];