nix: move withtmpdb to separate file

Co-authored-by: Remo Rechkemmer <59358383+monacoremo@users.noreply.github.com>

nix/tests.nix

@@ -17,29 +17,10 @@
 , postgrestProfiled
 , python3
 , runtimeShell
+, withTmpDb
 , yq
 }:
 let
-  # Wrap the `test/with_tmp_db` script with the required dependencies from Nix.
-  withTmpDb =
-    postgresql:
-    checkedShellScript
-      {
-        name = "postgrest-test-withtmpdb-${postgresql.name}";
-        docs = "Run the given command in a temporary database";
-        inRootDir = true;
-      }
-      ''
-        # avoid starting multiple layers of with_tmp_db
-        if test ! -v PGRST_DB_URI; then
-          export PATH=${postgresql}/bin:"$PATH"
-
-          exec test/with_tmp_db "$@"
-        else
-          "$@"
-        fi
-      '';
-
   # Create a `withPostgresql` for each PostgreSQL version that we want to test
   # against.
   withPostgresqlVersions =

nix/withtmpdb.nix

@@ -0,0 +1,20 @@
+# Wrap the `test/with_tmp_db` script with the required dependencies from Nix.
+{ checkedShellScript }:
+
+postgresql:
+checkedShellScript
+{
+  name = "postgrest-test-withtmpdb-${postgresql.name}";
+  docs = "Run the given command in a temporary database";
+  inRootDir = true;
+}
+  ''
+    # avoid starting multiple layers of with_tmp_db
+    if test ! -v PGRST_DB_URI; then
+      export PATH=${postgresql}/bin:"$PATH"
+
+      exec test/with_tmp_db "$@"
+    else
+      "$@"
+    fi
+  ''