Add an option to overwrite any existing config

Author: sandydoo

modules/pre-commit.nix

@@ -290,6 +290,18 @@ in
           '';
       };
 
+      overwriteConfig =
+        mkOption {
+          type = types.bool;
+          default = false;
+          description =
+            ''
+              Whether to overwrite any existing config at `configPath`.
+
+              When enabled, any existing config will be overwritten without prompting.
+            '';
+        };
+
       src =
         lib.mkOption {
           description = ''
@@ -397,7 +409,6 @@ in
 
   config =
     {
-
       rawConfig =
         {
           repos =
@@ -430,12 +441,17 @@ in
               echo 1>&2 "git-hooks.nix: updating $PWD repo"
               [ -L ${cfg.configPath} ] && unlink ${cfg.configPath}
 
-              if [ -e "''${GIT_WC}/${cfg.configPath}" ]; then
-                echo 1>&2 "git-hooks.nix: WARNING: Refusing to install because of pre-existing ${cfg.configPath}"
-                echo 1>&2 "    1. Translate ${cfg.configPath} contents to the new syntax in your Nix file"
-                echo 1>&2 "        see https://github.com/cachix/git-hooks.nix#getting-started"
-                echo 1>&2 "    2. remove ${cfg.configPath}"
-                echo 1>&2 "    3. add ${cfg.configPath} to .gitignore"
+              if [ -e "''${GIT_WC}/${cfg.configPath}" && ! ${boolToString cfg.overwriteConfig} ]; then
+                echo 1>&2 "git-hooks.nix: WARNING: Refusing to install because of an existing config at ${cfg.configPath}"
+                echo 1>&2 ""
+                echo 1>&2 "  To migrate the existing config to a Nix configuration:"
+                echo 1>&2 "    1. Translate the contents of ${cfg.configPath} into a Nix configuration."
+                echo 1>&2 "       See https://github.com/cachix/git-hooks.nix#getting-started"
+                echo 1>&2 "    2. Remove ${cfg.configPath}"
+                echo 1>&2 "    3. Add ${cfg.configPath} to .gitignore"
+                echo 1>&2 ""
+                echo 1>&2 "  To always overwrite the existing config, enable `overwriteConfig` in Nix."
+
               else
                 if ${boolToString cfg.addGcRoot}; then
                   nix-store --add-root "''${GIT_WC}/${cfg.configPath}" --indirect --realise ${cfg.configFile}