This represents the first step in migrating `home.file` to support
arbitrary absolute paths. This is to allow Home Manager to manage
files anywhere, provided the user has sufficient privileges.
For example, with this change the configuration
home.file."test/one".text = "foo";
home.file."/test/two".text = "foo";
will result in the files "$HOME/test/one" and "/test/two",
respectively. Note, a relative file name will still be relative
`$HOME`.
To allow a reasonable transition between the old and new path handling
we introduce the notion of "generation directory layout version". The
version is simply a file `version` within the generation directory
containing a number indicating the version number.
The version 0 (also implied if the version file is missing) indicates
the legacy layout where managed file paths always are relative
`$HOME`.
Version 1 indicates the new layout where managed file paths are
relative `/`.
This adds an empty `nix-build` command to verify that the user is
having a good Nix install. It also, as a side effect, will create the
necessary per-user `profiles` and `gcroots` directories.
Fixes#1246
Using the `nix-env` command is far more robust. It also has the
benefit that if the per-user `profiles` and `gcroots` directories do
not exist then they will be created with the correct permissions.
Because of the second point this commit also removes the `mkdir` step
of the installation instructions.
PR #1239Closes#474, #948, #1091
It is safest to use the system install of Nix since that will be
compatible with the running nix-daemon and/or databases.
Also add a printout of the used Nix version in the activation script
when running in verbose mode.
Fixes#218.
