add devshell

.envrc

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+# ^ added for shellcheck and file-type detection
+
+# Watch & reload direnv on change
+watch_file devshell.toml
+
+if [[ $(type -t use_flake) != function ]]; then
+  echo "ERROR: use_flake function missing."
+  echo "Please update direnv to v2.30.0 or later."
+  exit 1
+fi
+use flake

devshell.toml

@@ -0,0 +1,4 @@
+# https://numtide.github.io/devshell
+[[commands]]
+package = "devshell.cli"
+help = "Per project developer environments"

flake.lock

@@ -0,0 +1,92 @@
+{
+  "nodes": {
+    "devshell": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      },
+      "locked": {
+        "lastModified": 1658746384,
+        "narHash": "sha256-CCJcoMOcXyZFrV1ag4XMTpAPjLWb4Anbv+ktXFI1ry0=",
+        "owner": "numtide",
+        "repo": "devshell",
+        "rev": "0ffc7937bb5e8141af03d462b468bd071eb18e1b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "devshell",
+        "type": "github"
+      }
+    },
+    "flake-utils": {
+      "locked": {
+        "lastModified": 1642700792,
+        "narHash": "sha256-XqHrk7hFb+zBvRg6Ghl+AZDq03ov6OshJLiSWOoX5es=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "846b2ae0fc4cc943637d3d1def4454213e203cba",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "flake-utils_2": {
+      "locked": {
+        "lastModified": 1656928814,
+        "narHash": "sha256-RIFfgBuKz6Hp89yRr7+NR5tzIAbn52h8vT6vXkYjZoM=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "7e2a3b3dfd9af950a856d66b0a7d01e3c18aa249",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1643381941,
+        "narHash": "sha256-pHTwvnN4tTsEKkWlXQ8JMY423epos8wUOhthpwJjtpc=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "5efc8ca954272c4376ac929f4c5ffefcc20551d5",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_2": {
+      "locked": {
+        "lastModified": 1659782844,
+        "narHash": "sha256-tM/qhHFE61puBxh9ebP3BIG1fkRAT4rHqD3jCM0HXGY=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "c85e56bb060291eac3fb3c75d4e0e64f6836fcfe",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "type": "indirect"
+      }
+    },
+    "root": {
+      "inputs": {
+        "devshell": "devshell",
+        "flake-utils": "flake-utils_2",
+        "nixpkgs": "nixpkgs_2"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,20 @@
+{
+  description = "virtual environments";
+
+  inputs.devshell.url = "github:numtide/devshell";
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+
+  outputs = { self, flake-utils, devshell, nixpkgs }:
+    flake-utils.lib.eachDefaultSystem (system: {
+      devShell =
+        let pkgs = import nixpkgs {
+          inherit system;
+
+          overlays = [ devshell.overlay ];
+        };
+        in
+        pkgs.devshell.mkShell {
+          imports = [ (pkgs.devshell.importTOML ./devshell.toml) ];
+        };
+    });
+}