Document pre-commit hook for staged files

docs/pages/gettingstarted/git-pre-commit-hook.md

@@ -10,7 +10,7 @@ summary:
 Detekt can be integrated into your development workflow by using a Git pre-commit hook.
 For that reason Git supports to run custom scripts automatically, when a specific action occurs.
 The mentioned pre-commit hook can be setup locally on your dev-machine.
-The following client-side detekt hook is triggered by a commit operation.
+The following client-side detekt hook is triggered by a commit operation, and checks all files via the gradle task.
 
 ```bash
 #!/usr/bin/env bash
@@ -38,3 +38,47 @@ More information about Git hooks and how to install them can be found in
 A special thanks goes to Mohit Sarveiya for providing this shell script.
 You can watch his excellent talk about **Static Code Analysis For Kotlin** on 
 [YouTube](https://www.youtube.com/watch?v=LT6m5_LO2DQ).
+
+## Only run on staged files
+
+It is also possible to use [the CLI](cli.md) to create a hook that only runs on staged files. This has the advantage of speedier execution, by running on fewer files and avoiding the warm-up time of the gradle daemon.
+
+Please note, however, that a handful of checks requiring [type resolution](type-resolution.md) will not work correctly with this approach. If you do adopt a partial hook, it is recommended that you still implement a full `detekt` check as part of your CI pipeline.
+
+This example has been put together using [pre-commit](https://pre-commit.com/), but the same principle can be applied to any kind of hook. 
+
+Hook definition in pre-commit:
+
+```yml
+- id: detekt
+  name: detekt check
+  description: Runs `detekt` on modified .kt files.
+  language: script
+  entry: detekt.sh
+  files: \.kt
+```
+
+Script `detekt.sh`:
+
+```bash
+#!/bin/bash
+
+echo "Running detekt check..."
+fileArray=($@)
+detektInput=$(IFS=,;printf  "%s" "${fileArray[*]}")
+echo "Input files: $detektInput"
+
+OUTPUT="/tmp/detekt-$(date +%s)"
+detekt --input "$detektInput" > $OUTPUT
+EXIT_CODE=$?
+if [ $EXIT_CODE -ne 0 ]; then
+  cat $OUTPUT
+  rm $OUTPUT
+  echo "***********************************************"
+  echo "                 Detekt failed                 "
+  echo " Please fix the above issues before committing "
+  echo "***********************************************"
+  exit $EXIT_CODE
+fi
+rm $OUTPUT
+```