Rename the "markdown" Meson flag to "lowdown"

This is because we are about to use `cmark`. (Mored details in the next
commit.) We don't need this flag, or any other, to control the `cmark`
dependency --- it can just be unconditional. The name "lowdown" makes
clear that the original flag is just about lowdown, and no longer about
markdown in general.

packaging/hydra.nix

@@ -176,14 +176,14 @@ rec {
 
   # Toggles some settings for better coverage. Windows needs these
   # library combinations, and Debian build Nix with GNU readline too.
-  buildReadlineNoMarkdown =
+  buildReadlineNoLowdown =
     let
       components = forAllSystems (
         system:
         nixpkgsFor.${system}.native.nixComponents2.overrideScope (
           self: super: {
             nix-cmd = super.nix-cmd.override {
-              enableMarkdown = false;
+              enableLowdown = false;
               readlineFlavor = "readline";
             };
           }

src/libcmd/meson.build

@@ -35,7 +35,7 @@ deps_public += nlohmann_json
 lowdown = dependency(
   'lowdown',
   version : '>= 0.9.0',
-  required : get_option('markdown'),
+  required : get_option('lowdown'),
 )
 deps_private += lowdown
 configdata.set('HAVE_LOWDOWN', lowdown.found().to_int())

src/libcmd/meson.options

@@ -1,9 +1,9 @@
 # vim: filetype=meson
 
 option(
-  'markdown',
+  'lowdown',
   type : 'feature',
-  description : 'Enable Markdown rendering in the Nix binary (requires lowdown)',
+  description : 'Use the \'lowdown\' library to display colored Markdown in the terminal',
 )
 
 option(

src/libcmd/package.nix

@@ -19,7 +19,7 @@
   version,
 
   # Whether to enable Markdown rendering in the Nix binary.
-  enableMarkdown ? !stdenv.hostPlatform.isWindows,
+  enableLowdown ? !stdenv.hostPlatform.isWindows,
 
   # Which interactive line editor library to use for Nix's repl.
   #
@@ -54,7 +54,7 @@ mkMesonLibrary (finalAttrs: {
   buildInputs = [
     ({ inherit editline readline; }.${readlineFlavor})
   ]
-  ++ lib.optional enableMarkdown lowdown;
+  ++ lib.optional enableLowdown lowdown;
 
   propagatedBuildInputs = [
     nix-util
@@ -67,7 +67,7 @@ mkMesonLibrary (finalAttrs: {
   ];
 
   mesonFlags = [
-    (lib.mesonEnable "markdown" enableMarkdown)
+    (lib.mesonEnable "lowdown" enableLowdown)
     (lib.mesonOption "readline-flavor" readlineFlavor)
   ];