m1n1: replace withBranding with customLogo parameter

This avoids having to use `overrideAttrs` to customize the logo
installation and instead places the interface as an argument which
represents a file path to the desired image which will be
resized by imagemagick to 128x128 and 256x256.

This means that the same image will be used for both sizes (which
should be the intended case) but that can be circumvented manually via
`overrideAttrs` if desired (rather than "when needed").

It also adds documentation for this argument within
`meta.longDescription` for m1n1.

pkgs/by-name/m1/m1n1/package.nix

@@ -7,7 +7,7 @@
   python3Packages,
   nix-update-script,
   nixos-icons,
-  withBranding ? true,
+  customLogo ? "${nixos-icons}/share/icons/hicolor/256x256/apps/nix-snowflake.png",
 }:
 stdenv.mkDerivation (finalAttrs: {
   pname = "m1n1";
@@ -20,9 +20,9 @@ stdenv.mkDerivation (finalAttrs: {
     hash = "sha256-J1PZVaEdI6gx/qzsoVW1ehRQ/ZDKzdC1NgIGgBqxQ+0=";
   };
 
-  postPatch = lib.optionalString withBranding ''
-    ln -s ${nixos-icons}/share/icons/hicolor/128x128/apps/nix-snowflake.png data/custom_128.png
-    ln -s ${nixos-icons}/share/icons/hicolor/256x256/apps/nix-snowflake.png data/custom_256.png
+  postPatch = lib.optionalString (customLogo != null) ''
+    magick ${customLogo} -resize 128x128 data/custom_128.png
+    magick ${customLogo} -resize 256x256 data/custom_256.png
   '';
 
   nativeBuildInputs = [
@@ -40,7 +40,7 @@ stdenv.mkDerivation (finalAttrs: {
   makeFlags = [
     "ARCH=${stdenv.cc.targetPrefix}"
     "RELEASE=1"
-    (lib.optionalString withBranding "LOGO=custom")
+    (lib.optionalString (customLogo != null) "LOGO=custom")
   ];
 
   enableParallelBuilding = true;
@@ -94,6 +94,11 @@ stdenv.mkDerivation (finalAttrs: {
          - Initramfs images (compressed CPIO archives)
          - Kernel images in Linux ARM64 boot format (optionally compressed)
          - Configuration statements
+
+      The default Nix logo can be disabled by setting the `customLogo`
+      argument to `null` or can be replaced by setting `customLogo` to
+      a path to the desired image file which will be resized by
+      ImageMagick to the correct sizes.
     '';
     homepage = "https://github.com/AsahiLinux/m1n1";
     changelog = "https://github.com/AsahiLinux/m1n1/releases/tag/${finalAttrs.src.tag}";