home-manager's generated completions shadow built-in completion scripts.
fish actually has logic to deal with this when the path ends with
/generated_completions, so let's take advantage of it.
Link: 47c773300a/src/autoload.rs (L421-L424)
Instead of having to manually stub packages that should not be
downloaded we instead automatically stub all packages (except a small
list of whitelisted ones). Tests can re-introduce the real package by
using the `realPkgs` module argument.
This commit changes the way aliases are rendered, adding the "no more
flags" flag `--`, which means that, for example, the alias `"-" = "cd
-";` will work as expected. (I was getting a syntax error before this
change.)
Additionally, now the alias key is shell escaped, which may help some
edge cases. I'm honestly not sure if this part is necessary since I
assume an alias can't contain spaces anyway, but it definitely
shouldn't break anything.
