chore(tools/depotfmt): use Go version from buildGo

This is required because Go 1.18 is actually being deleted. I've
applied the formatting breakage that it introduces (such as breaking
comment formatting), because I can't be bothered to try and work
around broken Go stuff.

Change-Id: Ica7cee0d01228845d6a766079fef36df99a3da96
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9832
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

nix/buildGo/default.nix

@@ -118,4 +118,7 @@ in
   program = makeOverridable program;
   package = makeOverridable package;
   external = makeOverridable external;
+
+  # re-expose the Go version used
+  inherit go;
 }

tools/depotfmt.nix

@@ -9,10 +9,9 @@ let
     echo "$@" | xargs -n1 ${pkgs.terraform}/bin/terraform fmt
   '';
 
-  # TODO: Upgrade to Go 1.19 and reformat tree
   config = pkgs.writeText "depot-treefmt-config" ''
     [formatter.go]
-    command = "${pkgs.go_1_18}/bin/gofmt"
+    command = "${depot.nix.buildGo.go}/bin/gofmt"
     options = [ "-w" ]
     includes = ["*.go"]
 

tools/nixery/layers/layers.go

@@ -11,10 +11,10 @@
 //
 // # Inputs
 //
-// * a graph of Nix runtime dependencies, generated via exportReferenceGraph
+//   - a graph of Nix runtime dependencies, generated via exportReferenceGraph
-// * popularity values of each package in the Nix package set (in the form of a
+//   - popularity values of each package in the Nix package set (in the form of a
 //     direct reference count)
-// * a maximum number of layers to allocate for the image (the "layer budget")
+//   - a maximum number of layers to allocate for the image (the "layer budget")
 //
 // # Algorithm
 //
@@ -30,6 +30,7 @@
 // │     │
 // │     v
 // └───> D ───> F
+//
 //	│
 //	└────> G
 //