I've made this use functions to make it easier to add support for more
bootloaders. Seeing as there will be a big diff anyway I've also adjusted
the formatting to make it pep8 compliant.
...with the `sysroot.bootloader` configuration option. This can be useful
when converting a system to use `ostree` which doesn't currently have a
bootloader configuration that `ostree` can automatically detect, and is
also useful in combination with the `--sysroot` option when provisioning a
rootfs for systems other than the one you're running `ostree admin deploy`
on.
It's easier to extend and it centralises the config parsing. In other
places we will no longer need to use `g_str_equal` to match these values,
a `switch` statement will be sufficient.
We use a similar trick to having a `sysroot -> .` symlink on the real root
here to support both /boot on root as well as on a separate filesystem. No
matter how it's mounted `/boot/xyz` will always refer to the file you'd
expect.
This is nicer than my previous attempts at this because there's no
configuration nor auto-detection required.