Modify --version flag to show debugging information

default.nix

@@ -3,16 +3,17 @@
 }:
 
 let
-  inherit (pkgs) lib;
-  dirty = lib.optionalString (!(self ? rev)) "_dirty";
-  version = "0.1.0+git${self.lastModifiedDate}${dirty}";
+  shortRev = self.shortRev or "dirty";
+  version = "0.1.0+git_${shortRev}";
 in
 {
   nix-alien = pkgs.callPackage ./nix-alien.nix {
     inherit version;
     inherit (self.inputs) nix-filter;
     nix-index = self.inputs.nix-index-database.packages.${pkgs.system}.nix-index-with-db;
-    nixpkgs-src = self.inputs.nix-index-database.inputs.nixpkgs.sourceInfo;
+    nix-index-database-src = self.inputs.nix-index-database;
+    nixpkgs-build-src = self.inputs.nixpkgs;
+    nixpkgs-src = self.inputs.nix-index-database.inputs.nixpkgs;
   };
 
   # For backwards compat, may be removed in the future

nix-alien.nix

@@ -1,12 +1,10 @@
 { lib
 , fzf
-, nix-index
 , nix-filter
-, nixpkgs-src ? {
-    lastModifiedDate = "19700101000000";
-    rev = "nixpkgs-unstable";
-    narHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
-  }
+, nix-index
+, nix-index-database-src
+, nixpkgs-build-src
+, nixpkgs-src
 , python3
 , version
 }:
@@ -50,7 +48,11 @@ python3'.pkgs.buildPythonApplication {
   ] ++ (lib.attrVals deps python3'.pkgs);
 
   preBuild = ''
-    echo "__version__ = \"${version}\"" > nix_alien/_version.py
+    substituteInPlace nix_alien/_version.py \
+      --subst-var-by version ${version} \
+      --subst-var-by nixIndexDatabaseRev ${nix-index-database-src.rev} \
+      --subst-var-by nixpkgsRev ${nixpkgs-src.rev} \
+      --subst-var-by nixpkgsBuildRev ${nixpkgs-build-src.rev}
     substituteInPlace {nix_alien,tests}/*.{py,nix} \
       --subst-var-by nixpkgsLastModifiedDate ${nixpkgs-src.lastModifiedDate} \
       --subst-var-by nixpkgsRev ${nixpkgs-src.rev} \

nix_alien/_impl.py

@@ -9,7 +9,7 @@
 from platform import machine
 from typing import Callable, Optional
 
-from ._version import __version__
+from ._version import version
 from .helpers import edit_file, get_dest_path, get_print, read_template
 from .libs import find_libs, get_unique_packages
 
@@ -160,7 +160,7 @@ def main(
 
     parser = argparse.ArgumentParser()
     parser.add_argument("program", help="Program to run")
-    parser.add_argument("--version", action="version", version=__version__)
+    parser.add_argument("--version", action="version", version=version)
     parser.add_argument(
         "-l",
         "--additional-libs",

nix_alien/_version.py

@@ -1 +1,17 @@
-__version__ = "0.1.0+unknown"
+__version__ = "@version@"
+__nix_index_database_rev__ = "@nixIndexDatabaseRev@"
+# They should always be the same unless the user overrides them
+__nixpkgs_rev__ = "@nixpkgsRev@"
+__nixpkgs_build_rev__ = "@nixpkgsBuildRev@"
+
+if __nixpkgs_rev__ != __nixpkgs_build_rev__:
+    nixpkgs_build_rev = f"nixpkgs-build={__nixpkgs_build_rev__}"
+else:
+    nixpkgs_build_rev = ""
+
+version = f"""
+version={__version__}
+nix-index-database={__nix_index_database_rev__}
+nixpkgs={__nixpkgs_rev__}
+{nixpkgs_build_rev}
+"""