This requires us to avoid the `tryEval` + `throw` combination,
because throw is strict in its error message, and we don't want
to drop our single clue when `commitIdFromGitRepo` is used
incorrectly.
It gives a warning on the lazy-trees branch of Nix
(NixOS/nix#6530)
"warning: applying 'toString' to path '...' and then accessing it is deprecated, at '...'"
'else toString (/. + "${base}/${path}");' at line 183 may still cause a warning but i don't know how
to reach that codepath and test so im leaving it untouched
changing it to 'else /. + "${base}/${path}";'
caused this error
```
error: a string that refers to a store path cannot be appended to a path
at /home/systems/nixpkgs/lib/sources.nix:183:20:
182| then path
183| else /. + "${base}/${path}";
| ^
184| in if pathIsRegularFile path
```
It gives a warning on the lazy-trees branch of Nix
(NixOS/nix#6530)
one of these was also giving me an error (the one in lib/trivial probably)
```
$ nix build
warning: applying 'toString' to path '/home/artturin/nixgits/my-nixpkgs/nixos/modules/installer/sd-card/sd
-image-aarch64.nix' and then accessing it is deprecated, at /home/artturin/nixgits/my-nixpkgs/lib/modules.
nix:349:99
warning: applying 'toString' to path '/home/artturin/nixgits/my-nixpkgs/.git' and then accessing it is dep
recated, at /home/artturin/nixgits/my-nixpkgs/lib/sources.nix:35:32
warning: applying 'toString' to path '/home/artturin/nixgits/my-nixpkgs/nixos/modules/system/etc/etc.nix'
and then accessing it is deprecated, at «stdin»:0
warning: applying 'toString' to path '/home/artturin/nixgits/my-nixpkgs/nixos/modules/system/etc/etc-activ
ation.nix' and then accessing it is deprecated, at «stdin»:0
warning: applying 'toString' to path '/home/artturin/nixgits/my-nixpkgs/nixos/modules/installer/sd-card/sd
-image-aarch64.nix' and then accessing it is deprecated, at «stdin»:0
error: cannot decode virtual path '/nix/store/virtual0000000000000000000000005-source'
(use '--show-trace' to show detailed location information)
```
A tricky thing about FreeBSD is that there is no stable ABI across
versions. That means that putting in the version as part of the config
string is paramount.
We have a parsed represenation that separates name versus version to
accomplish this. We include FreeBSD versions 12 and 13 to demonstrate
how it works.
