When building MacVim with nix-daemon it tries to place the derived data
into a path rooted in `/var/empty`, which fails. Specifying the derived
data path ourselves fixes this problem.
See db236e588d "steam: Do $PATH lookup in steam.desktop [...]".
tl;dr: Otherwise widget/panel/desktop icons in DEs like KDE break.
Simply stop adding the full derivation path for neovim and stick with
how upstream uses no path at all.
While here, take care of gnvim.desktop as well by adjusting the sed(1)
expression (and simplifying it in one go); I do not use gnvim.desktop
but built it and confirmed the resulting files to contain no full paths
any longer.
So, kakoune takes the documentation shown for `:doc` from
`$KAKOUNE_RUNTIME/share/kak/doc`. Unfortunately, it seems
that it will ignore files that are symlinks. This is arguably
a bug in kakoune, we workaround it for now by copying the
content of the docfiles.
The previous implementation of plugin-support for the kakoune derivation
was based on generating, at build time, a `plugins.kak` file that would
source all .kak files in the list of plugins, and wrap the `kak` binary
in a script that would add some command-line arguments so that this
file gets loaded on start-up. The main problem with this approach
is that the plugins' code get executed *after* the user's configuration
file is loaded, so effectively one cannot automatically activate/configure
these plugins.
The idiomatic way of loading plugins is ensuring they end up installed
somwhere under `share/kak/autoload`. Because plugins are already being
packaged to have their code in `share/kak/autoload/plugins/<name-of-plugin>`,
we can obtain a derivation that includes the plugins simply by doing a
`symlinkJoin` of `kakoune-unwrapped` and all the requested plugins.
For this to work, we need to fix two issues:
1. By default, kakoune makes `share/kak/autoload` a symbolic link to
`share/kak/rc`, which contains all builtin definitions. We need
to patch this to put the symlink under `share/kak/autoload/rc`, so that
the join works.
2. By default kakoune expects the `autoload` directory to be in
`../share/kak/autoload` relative to the location of the `kak` binary.
We need to set the `KAKOUNE_RUNTIME` to point the symlinked
share/kak for this to work.
