Rename `nix show-config` to `nix config show`

Part of #7672

My main motivation is to be able to use `nix.checkConfig`[1]. This
doesn't work with Lix currently since the module uses `nix show-config`
if the Nix version is <2.20pre and `nix config show` otherwise. I think
this is the only instance where nixpkgs checks for which Nix commands
exist that affects us now, so I figured we could just perform the rename
here as well[2] and still provide the current version number[3].

I don't have a strong opinion on whether to deprecate `nix show-config`,
the warning is added there automatically.

(cherry picked from commit f300e11b056dea414d7d77bbc6e5a7dc5d9ddd41)

[1] https://nixos.org/manual/nixos/stable/options.html#opt-nix.checkConfig
[2] I should add that I don't use the "official" ways of installing Lix
    because using the flake directly and callPackaging it seemed to fit
    better into my workflow: I already have a little mess to make
    sure Hydra from the flake uses the correct pkgs.nix and I didn't
    want to complicate it further while keeping a single package-set I
    can build in CI. Don't get me wrong, I think such a module for a
    quick-start is very important, just giving context on why I bother
    in the first place :)
[3] When we go public, I think it's worth considering to add support in
    nixpkgs itself for Lix.

Change-Id: I47b4239b05cbeda3c370d2fa56ea768b768768ac

1 files changed, 2 insertions, 1 deletions

diff --git a/doc/manual/meson.build b/doc/manual/meson.build
index cfb6be36f..e253a9bd8 100644
--- a/doc/manual/meson.build
+++ b/doc/manual/meson.build
@@ -197,6 +197,8 @@ endforeach
 nix3_manpages = [
   'nix3-build',
   'nix3-bundle',
+  'nix3-config',
+  'nix3-config-show',
   'nix3-copy',
   'nix3-daemon',
   'nix3-derivation-add',
@@ -258,7 +260,6 @@ nix3_manpages = [
   'nix3-run',
   'nix3-search',
   'nix3-shell',
-  'nix3-show-config',
   'nix3-store-add-file',
   'nix3-store-add-path',
   'nix3-store-cat',