Nix: Set build revision based on git SHA

default.nix

@@ -1,4 +1,4 @@
-{ pkgs ? import <nixpkgs> { } }:
+{ pkgs ? import <nixpkgs> {}, gitSha }:
   pkgs.rustPlatform.buildRustPackage {
     pname = "amp";
     version = "0.7.0";
@@ -13,8 +13,26 @@
     # Packages needed during the build
     nativeBuildInputs = with pkgs; [ git ];
 
+    # Make the build/check/install commands explicit so we can
+    # provide the commit SHA for the splash screen
+    buildPhase = ''
+      export BUILD_REVISION=${builtins.substring 0 7 gitSha}
+      echo "BUILD_REVISION=$BUILD_REVISION"
+
+      cargo build --release
+    '';
+
+    checkPhase = ''
+      cargo test
+    '';
+
+    installPhase = ''
+      mkdir -p $out/bin
+      cp target/release/amp $out/bin/
+    '';
+
     # Amp creates files and directories in $HOME/.config/amp when run.
     # Since the checkPhase of the build process runs the test suite, we
     # need a writable location to avoid permission error test failures.
-    HOME="$out";
+    HOME="$src";
   }

flake.nix

@@ -12,7 +12,7 @@
       pkgsFor = nixpkgs.legacyPackages;
     in {
       packages = forAllSystems (system: {
-        default = pkgsFor.${system}.callPackage ./. { };
+        default = pkgsFor.${system}.callPackage ./. { gitSha = self.rev; };
       });
     };
 }