cmd/nix-tool: override context for chroot store

cmd/nix-tool/chroot.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"context"
+	"os/exec"
+
+	"gensokyo.uk/nix"
+)
+
+type chrootStoreContext struct {
+	store string
+	nix.Context
+}
+
+func (c *chrootStoreContext) Nix(ctx context.Context, arg ...string) *exec.Cmd {
+	return c.Context.Nix(ctx, append([]string{"--store", c.store}, arg...)...)
+}

cmd/nix-tool/main.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"os/signal"
 	"slices"
+	"strings"
 	"syscall"
 
 	"gensokyo.uk/nix"
@@ -27,6 +28,7 @@ func main() {
 	defer stop()
 
 	var (
+		flagStore   string
 		flagNixOS   bool
 		flagVerbose bool
 		flagJSON    bool
@@ -40,8 +42,14 @@ func main() {
 		}
 		ctx = nix.New(nixCtx, nil, os.Stdout, stderr)
 
+		flagStore = strings.TrimSpace(flagStore)
+		if flagStore != string(os.PathSeparator) {
+			ctx = &chrootStoreContext{flagStore, ctx}
+		}
+
 		return nil
 	}).
+		Flag(&flagStore, "store", command.StringFlag("/"), "Path to the nix root").
 		Flag(&flagNixOS, "nixos", command.BoolFlag(false), "Interpret input as NixOS flake installable").
 		Flag(&flagVerbose, "v", command.BoolFlag(false), "Connect nix stderr").
 		Flag(&flagJSON, "json", command.BoolFlag(false), "Serialise output in JSON when applicable")