feat: support specifying stages

modules/pre-commit.nix

@@ -17,6 +17,8 @@ let
   inherit (pkgs) runCommand writeText git;
 
   cfg = config.pre-commit;
+  # TODO: add per-hook stages to install here
+  install_stages = cfg.default_stages;
 
   hookType =
     types.submodule (
@@ -258,6 +260,18 @@ in
           default = [];
         };
 
+      default_stages =
+        mkOption {
+          type = types.listOf types.str;
+          description =
+            ''
+              A configuration wide option for the stages property.
+              Installs hooks to the defined stages.
+              Default is empty which falls back to 'commit'.
+            '';
+          default = [];
+        };
+
       rawConfig =
         mkOption {
           type = types.attrs;
@@ -286,6 +300,8 @@ in
             ];
         } // lib.optionalAttrs (cfg.excludes != []) {
           exclude = mergeExcludes cfg.excludes;
+        } // lib.optionalAttrs (cfg.default_stages != []) {
+          default_stages = cfg.default_stages;
         };
 
       pre-commit.installationScript =
@@ -315,7 +331,36 @@ in
                 echo 1>&2 "    3. add .pre-commit-config.yaml to .gitignore"
               else
                 ln -s ${configFile} .pre-commit-config.yaml
-                pre-commit install
+                # Remove any previously installed hooks (since pre-commit itself has no convergent design)
+                hooks="pre-commit pre-merge-commit pre-push prepare-commit-msg commit-msg post-checkout post-commit"
+                for hook in $hooks; do
+                  pre-commit uninstall -t $hook
+                done
+                # Add hooks for configured stages (only) ...
+                if [ ! -z "${concatStringsSep " " install_stages}" ]; then
+                  for stage in ${concatStringsSep " " install_stages}; do
+                    if [[ "$stage" == "manual" ]]; then
+                      continue
+                    fi
+                    case $stage in
+                      # if you amend these switches please also review $hooks above
+                      commit | merge-commit | push)
+                        stage="pre-"$stage
+                        pre-commit install -t $stage
+                        ;;
+                      prepare-commit-msg | commit-msg | post-checkout | post-commit)
+                        pre-commit install -t $stage
+                        ;;
+                      *)
+                        echo 1>&2 "ERROR: nix-pre-commit-hooks: either $stage is not a valid stage or pre-commit-hooks.nix doesn't yet support it."
+                        exit 1
+                        ;;
+                    esac
+                  done
+                # ... or default 'pre-commit' hook
+                else
+                  pre-commit install
+                fi
               fi
             fi
           fi

nix/run.nix

@@ -5,6 +5,7 @@ builtinStuff@{ pkgs, tools, pre-commit, git, runCommand, writeText, writeScript,
 , excludes ? []
 , tools ? {}
 , settings ? {}
+, default_stages ? []
 }:
 
 let
@@ -32,7 +33,7 @@ let
                 _module.args.pkgs = pkgs;
                 pre-commit =
                   {
-                    inherit hooks excludes settings;
+                    inherit hooks excludes settings default_stages;
                     tools = builtinStuff.tools // tools;
                   };
               };