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add git pre push hook (#2553)
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‎CHANGES.md

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@@ -12,6 +12,7 @@ We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (
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## [Unreleased]
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### Added
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* Allow specifying path to Biome JSON config file directly in `biome` step. Requires biome 2.x. ([#2548](https://github.com/diffplug/spotless/pull/2548))
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- `GitPrePushHookInstaller`, a reusable library component for installing a Git `pre-push` hook that runs formatter checks.
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## Changed
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* Bump default `gson` version to latest `2.11.0` -> `2.13.1`. ([#2414](https://github.com/diffplug/spotless/pull/2414))

‎lib/src/main/java/com/diffplug/spotless/GitPrePushHookInstaller.java

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/*
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* Copyright 2025 DiffPlug
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.diffplug.spotless;
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import static java.nio.charset.StandardCharsets.UTF_8;
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import static java.util.Objects.requireNonNull;
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import java.io.File;
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import java.io.FileWriter;
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import java.io.IOException;
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import java.nio.file.Files;
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/**
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* Abstract class responsible for installing a Git pre-push hook in a repository.
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* This class ensures that specific checks and logic are run before a push operation in Git.
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*
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* Subclasses should define specific behavior for hook installation by implementing the required abstract methods.
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*/
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public abstract class GitPrePushHookInstaller {
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private static final String HOOK_HEADER = "##### SPOTLESS HOOK START #####";
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private static final String HOOK_FOOTER = "##### SPOTLESS HOOK END #####";
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/**
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* Logger for recording informational and error messages during the installation process.
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*/
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protected final GitPreHookLogger logger;
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/**
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* The root directory of the Git repository where the hook will be installed.
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*/
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protected final File root;
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/**
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* Constructor to initialize the GitPrePushHookInstaller with a logger and repository root path.
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*
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* @param logger The logger for recording messages.
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* @param root The root directory of the Git repository.
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*/
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public GitPrePushHookInstaller(GitPreHookLogger logger, File root) {
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this.logger = requireNonNull(logger, "logger can not be null");
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this.root = requireNonNull(root, "root file can not be null");
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}
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/**
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* Installs the Git pre-push hook into the repository.
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*
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* <p>This method checks for the following:
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* <ul>
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* <li>Ensures Git is installed and the `.git/config` file exists.</li>
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* <li>Checks if an executor required by the hook is available.</li>
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* <li>Creates and writes the pre-push hook file if it does not exist.</li>
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* <li>Skips installation if the hook is already installed.</li>
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* </ul>
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* If an issue occurs during installation, error messages are logged.
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*
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* @throws Exception if any error occurs during installation.
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*/
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public void install() throws Exception {
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logger.info("Installing git pre-push hook");
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if (!isGitInstalled()) {
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logger.error("Git not found in root directory");
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return;
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}
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var hookContent = "";
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final var gitHookFile = root.toPath().resolve(".git/hooks/pre-push").toFile();
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if (!gitHookFile.exists()) {
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logger.info("Git pre-push hook not found, creating it");
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if (!gitHookFile.getParentFile().exists() && !gitHookFile.getParentFile().mkdirs()) {
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logger.error("Failed to create pre-push hook directory");
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return;
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}
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if (!gitHookFile.createNewFile()) {
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logger.error("Failed to create pre-push hook file");
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return;
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}
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if (!gitHookFile.setExecutable(true, false)) {
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logger.error("Can not make file executable");
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return;
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}
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hookContent += "#!/bin/sh\n";
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}
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if (isGitHookInstalled(gitHookFile)) {
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logger.info("Git pre-push hook already installed, reinstalling it");
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uninstall(gitHookFile);
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}
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hookContent += preHookContent();
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writeFile(gitHookFile, hookContent, true);
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logger.info("Git pre-push hook installed successfully to the file %s", gitHookFile.getAbsolutePath());
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}
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/**
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* Uninstalls the Spotless Git pre-push hook from the specified hook file by removing
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* the custom hook content between the defined hook markers.
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*
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* <p>This method:
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* <ul>
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* <li>Reads the entire content of the pre-push hook file</li>
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* <li>Identifies the Spotless hook section using predefined markers</li>
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* <li>Removes the Spotless hook content while preserving other hook content</li>
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* <li>Writes the modified content back to the hook file</li>
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* </ul>
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*
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* @param gitHookFile The Git pre-push hook file from which to remove the Spotless hook
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* @throws Exception if any error occurs during the uninstallation process,
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* such as file reading or writing errors
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*/
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private void uninstall(File gitHookFile) throws Exception {
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final var hook = Files.readString(gitHookFile.toPath(), UTF_8);
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final int hookStart = hook.indexOf(HOOK_HEADER);
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final int hookEnd = hook.indexOf(HOOK_FOOTER) + HOOK_FOOTER.length(); // hookEnd exclusive, so must be last symbol \n
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/* Detailed explanation:
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* 1. hook.indexOf(HOOK_FOOTER) - finds the starting position of footer "##### SPOTLESS HOOK END #####"
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* 2. + HOOK_FOOTER.length() is needed because String.substring(startIndex, endIndex) treats endIndex as exclusive
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*
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* For example, if file content is:
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* #!/bin/sh
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* ##### SPOTLESS HOOK START #####
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* ... hook code ...
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* ##### SPOTLESS HOOK END #####
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* other content
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*
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* When we later use this in: hook.substring(hookStart, hookEnd)
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* - Since substring's endIndex is exclusive (it stops BEFORE that index)
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* - We need hookEnd to point to the position AFTER the last '#'
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* - This ensures the entire footer "##### SPOTLESS HOOK END #####" is included in the substring
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*
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* This exclusive behavior is why in the subsequent code:
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* if (hook.charAt(hookEnd) == '\n') {
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* hookScript += "\n";
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* }
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*
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* We can directly use hookEnd to check the next character after the footer
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* - Since hookEnd is already pointing to the position AFTER the footer
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* - No need for hookEnd + 1 in charAt()
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* - This makes the code more consistent with the substring's exclusive nature
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*/
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var hookScript = hook.substring(hookStart, hookEnd);
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if (hookStart >= 1 && hook.charAt(hookStart - 1) == '\n') {
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hookScript = "\n" + hookScript;
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}
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if (hookStart >= 2 && hook.charAt(hookStart - 2) == '\n') {
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hookScript = "\n" + hookScript;
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}
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if (hook.charAt(hookEnd) == '\n') {
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hookScript += "\n";
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}
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final var uninstalledHook = hook.replace(hookScript, "");
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writeFile(gitHookFile, uninstalledHook, false);
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}
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/**
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* Provides the content of the hook that should be inserted into the pre-push script.
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*
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* @return A string representing the content to include in the pre-push script.
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*/
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protected abstract String preHookContent();
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/**
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* Generates a pre-push template script that defines the commands to check and apply changes
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* using an executor and Spotless.
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*
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* @param executor The tool to execute the check and apply commands.
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* @param commandCheck The command to check for issues.
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* @param commandApply The command to apply corrections.
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* @return A string template representing the Spotless Git pre-push hook content.
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*/
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protected String preHookTemplate(String executor, String commandCheck, String commandApply) {
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var spotlessHook = "";
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spotlessHook += "\n";
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spotlessHook += "\n" + HOOK_HEADER;
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spotlessHook += "\nSPOTLESS_EXECUTOR=" + executor;
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spotlessHook += "\nif ! $SPOTLESS_EXECUTOR " + commandCheck + " ; then";
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spotlessHook += "\n echo 1>&2 \"spotless found problems, running " + commandApply + "; commit the result and re-push\"";
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spotlessHook += "\n $SPOTLESS_EXECUTOR " + commandApply;
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spotlessHook += "\n exit 1";
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spotlessHook += "\nfi";
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spotlessHook += "\n" + HOOK_FOOTER;
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spotlessHook += "\n";
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return spotlessHook;
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}
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/**
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* Checks if Git is installed by validating the existence of `.git/config` in the repository root.
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*
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* @return {@code true} if Git is installed, {@code false} otherwise.
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*/
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private boolean isGitInstalled() {
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return root.toPath().resolve(".git/config").toFile().exists();
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}
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/**
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* Verifies if the pre-push hook file already contains the custom Spotless hook content.
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*
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* @param gitHookFile The file representing the Git hook.
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* @return {@code true} if the hook is already installed, {@code false} otherwise.
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* @throws Exception if an error occurs when reading the file.
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*/
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private boolean isGitHookInstalled(File gitHookFile) throws Exception {
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final var hook = Files.readString(gitHookFile.toPath(), UTF_8);
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return hook.contains(HOOK_HEADER) && hook.contains(HOOK_FOOTER);
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}
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/**
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* Writes the specified content into a file.
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*
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* @param file The file to which the content should be written.
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* @param content The content to write into the file.
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* @throws IOException if an error occurs while writing to the file.
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*/
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private void writeFile(File file, String content, boolean append) throws IOException {
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try (final var writer = new FileWriter(file, UTF_8, append)) {
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writer.write(content);
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}
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}
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public interface GitPreHookLogger {
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void info(String format, Object... arguments);
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void warn(String format, Object... arguments);
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void error(String format, Object... arguments);
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}
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}

‎lib/src/main/java/com/diffplug/spotless/GitPrePushHookInstallerGradle.java

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/*
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* Copyright 2025 DiffPlug
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.diffplug.spotless;
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import java.io.File;
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/**
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* Implementation of {@link GitPrePushHookInstaller} specifically for Gradle-based projects.
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* This class installs a Git pre-push hook that uses Gradle's `gradlew` executable to check and apply Spotless formatting.
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*/
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public class GitPrePushHookInstallerGradle extends GitPrePushHookInstaller {
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/**
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* The Gradle wrapper file (`gradlew`) located in the root directory of the project.
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*/
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private final File gradlew;
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public GitPrePushHookInstallerGradle(GitPreHookLogger logger, File root) {
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super(logger, root);
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this.gradlew = root.toPath().resolve("gradlew").toFile();
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}
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/**
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* {@inheritDoc}
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*/
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@Override
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protected String preHookContent() {
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return preHookTemplate(executorPath(), "spotlessCheck", "spotlessApply");
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}
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private String executorPath() {
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if (gradlew.exists()) {
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return gradlew.getAbsolutePath();
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}
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logger.info("Gradle wrapper is not installed, using global gradle");
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return "gradle";
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}
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}

‎lib/src/main/java/com/diffplug/spotless/GitPrePushHookInstallerMaven.java

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/*
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* Copyright 2025 DiffPlug
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.diffplug.spotless;
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import java.io.File;
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/**
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* Implementation of {@link GitPrePushHookInstaller} specifically for Maven-based projects.
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* This class installs a Git pre-push hook that uses Maven to check and apply Spotless formatting.
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*/
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public class GitPrePushHookInstallerMaven extends GitPrePushHookInstaller {
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private final File mvnw;
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public GitPrePushHookInstallerMaven(GitPreHookLogger logger, File root) {
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super(logger, root);
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this.mvnw = root.toPath().resolve("mvnw").toFile();
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}
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/**
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* {@inheritDoc}
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*/
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@Override
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protected String preHookContent() {
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return preHookTemplate(executorPath(), "spotless:check", "spotless:apply");
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}
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private String executorPath() {
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if (mvnw.exists()) {
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return mvnw.getAbsolutePath();
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}
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logger.info("Maven wrapper is not installed, using global maven");
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return "mvn";
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}
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}

‎plugin-gradle/CHANGES.md

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## [Unreleased]
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### Added
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* Allow specifying path to Biome JSON config file directly in `biome` step. Requires biome 2.x. ([#2548](https://github.com/diffplug/spotless/pull/2548))
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- `spotlessInstallGitPrePushHook` task, which installs a Git `pre-push` hook to run `spotlessCheck` and `spotlessApply`.
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Uses shared implementation from `GitPrePushHookInstaller`.
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[#2553](https://github.com/diffplug/spotless/pull/2553)
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## Changed
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* Bump default `gson` version to latest `2.11.0` -> `2.13.1`. ([#2414](https://github.com/diffplug/spotless/pull/2414))

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