Set up GRUB and detect other OSes when updating the boot image

docs/commands.md

@@ -60,7 +60,7 @@ of the `blob` listing.
 
 | Command | Does | Arguments |
 | --- | --- | --- |
-| `blob-boot` | - | - |
+| `blob-boot` | Apply a boot splash, set up GRUB, and detect other operating systems | [image] \| grub [--purge] \| detect \| cleanup \| status |
 
 ## branding
 

docs/install.md

@@ -15,7 +15,7 @@ with `--check`.
 | `install/steps/packages.sh` | repo and AUR packages, and the yay bootstrap |
 | `install/steps/config.sh` | the `BLOB_PATH` symlink, everything under `~/.config`, and the login shell profile |
 | `install/steps/services.sh` | system services, systemd drop-ins, user units |
-| `install/steps/boot.sh` | the Plymouth boot splash |
+| `install/steps/boot.sh` | the Plymouth boot splash, GRUB, and other-OS detection |
 | `install/steps/theme.sh` | the wallpaper link, the first theme, the first background |
 | `install/steps/login.sh` | SDDM, the session entry, and the first launch |
 | `install/steps/reload.sh` | reloading systemd, the user services, and a running session |
@@ -81,7 +81,8 @@ with `--check`.
    holds the console and leaves the machine with neither a greeter nor a TTY.
    The installer then applies `branding/blob_boot.png` as the boot splash
    through `blob boot`, which installs the theme, adds the mkinitcpio hook,
-   unmasks the plymouth units and rebuilds the initramfs. It is skipped when
+   unmasks the plymouth units, rebuilds the initramfs, and sets GRUB up with
+   os-prober so other installed systems appear in the boot menu. It is skipped when
    the blob theme is already the default with the same image, and once it is
    in place the plymouth units are no longer masked on later runs. See
    [packages.md](packages.md#the-boot-splash).

docs/packages.md

@@ -152,9 +152,24 @@ TTY. `install.sh` therefore masks `plymouth-start.service` and
 `plymouth-quit-wait.service` until the splash is configured, and `blob boot`
 unmasks them as part of configuring everything else - the theme in
 `default/plymouth/`, the `plymouth` mkinitcpio hook, and the initramfs rebuild.
-It finishes by printing the kernel parameters your bootloader still needs
-(`quiet splash vt.global_cursor_default=0`), because that line is the one thing
-it will not rewrite for a bootloader other than GRUB.
+
+Every splash update then sets GRUB up to boot the machine and everything else
+on it:
+
+- With GRUB already installed, it makes sure `os-prober` is installed and
+  `GRUB_DISABLE_OS_PROBER=false`, adds whichever of `quiet splash
+  vt.global_cursor_default=0` is missing from `GRUB_CMDLINE_LINUX_DEFAULT`
+  without touching the rest of the line, and regenerates the menu. os-prober
+  finds other systems, Windows gets an explicit chainload entry when os-prober
+  misses it on a shared ESP, and the run stops if the menu has no Arch entry.
+- Without GRUB, it runs the same migration as `blob boot grub`: GRUB is
+  installed, other systems are detected, and GRUB is armed for one test boot
+  with Limine left as the standing default. Once that boot works,
+  `blob boot cleanup` retires Limine.
+- On a machine not booted in UEFI mode GRUB is left alone and the kernel
+  parameters the bootloader still needs are printed instead.
+
+`blob boot detect` reruns only the OS detection.
 
 ## Updating