add version tracking and release script

The derivation had no version, making it hard to tell which build a user
is running when debugging issues like #135. Add version.txt as the
single source of truth, referenced by default.nix via lib.fileContents.

The release script is adopted from nixpkgs-review to automate bumping
version.txt, tagging, and creating a GitHub draft release.

Author: Mic92

bin/create-release.sh

@@ -0,0 +1,42 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" >/dev/null && pwd)"
+cd "$SCRIPT_DIR/.."
+
+version="${1:-}"
+if [[ -z $version ]]; then
+  echo "USAGE: $0 version" >&2
+  exit 1
+fi
+
+if [[ "$(git symbolic-ref --short HEAD)" != "main" ]]; then
+  echo "must be on main branch" >&2
+  exit 1
+fi
+
+# ensure we are up-to-date
+uncommitted_changes=$(git diff --compact-summary)
+if [[ -n $uncommitted_changes ]]; then
+  echo -e "There are uncommitted changes, exiting:\n${uncommitted_changes}" >&2
+  exit 1
+fi
+git pull git@github.com:Mic92/nixos-shell main
+unpushed_commits=$(git log --format=oneline origin/main..main)
+if [[ $unpushed_commits != "" ]]; then
+  echo -e "\nThere are unpushed changes, exiting:\n$unpushed_commits" >&2
+  exit 1
+fi
+# make sure tag does not exist
+if git tag -l | grep -q "^${version}\$"; then
+  echo "Tag ${version} already exists, exiting" >&2
+  exit 1
+fi
+echo "$version" > version.txt
+git add version.txt
+git commit -m "bump version ${version}"
+git push origin main
+git tag "${version}"
+git push origin "${version}"
+gh release create "${version}" --draft --title "${version}" --generate-notes

default.nix

@@ -4,7 +4,7 @@
 
 with pkgs;
 stdenv.mkDerivation {
-  name = "nixos-shell";
+  name = "nixos-shell-${lib.fileContents ./version.txt}";
   src = builtins.filterSource
     (path: type: baseNameOf path != "nixos.qcow2" &&
                  baseNameOf path != ".git" &&

version.txt

@@ -0,0 +1 @@
+2.1.0