Exiting early in recipes:update if the index is not clean

Avoids problems later when we run "git update-index --refresh"

Author: weaverryan

src/Command/UpdateRecipesCommand.php

@@ -13,6 +13,7 @@
 
 use Composer\Command\BaseCommand;
 use Composer\IO\IOInterface;
+use Composer\Util\ProcessExecutor;
 use Symfony\Component\Console\Exception\RuntimeException;
 use Symfony\Component\Console\Formatter\OutputFormatterStyle;
 use Symfony\Component\Console\Input\InputArgument;
@@ -60,11 +61,20 @@ protected function configure()
     protected function execute(InputInterface $input, OutputInterface $output): int
     {
         $win = '\\' === \DIRECTORY_SEPARATOR;
+        $runtimeExceptionClass = class_exists(RuntimeException::class) ? RuntimeException::class : \RuntimeException::class;
         if (!@is_executable(strtok(exec($win ? 'where git' : 'command -v git'), \PHP_EOL))) {
-            throw new RuntimeException('Cannot run "recipes:update": git not found.');
+            throw new $runtimeExceptionClass('Cannot run "recipes:update": git not found.');
         }
 
         $io = $this->getIO();
+        if (!$this->isIndexClean($io)) {
+            $io->write([
+                '  Cannot run <comment>recipes:update</comment>: Your git index contains uncommitted changes.',
+                '  Please commit or stash them and try again!',
+            ]);
+
+            return 1;
+        }
 
         $packageName = $input->getArgument('package');
         $symfonyLock = $this->flex->getLock();
@@ -376,4 +386,18 @@ private function askForPackage(IOInterface $io, Lock $symfonyLock): ?string
 
         return $outdatedRecipes[$choice];
     }
+
+    private function isIndexClean(IOInterface $io): bool
+    {
+        $processExecutor = new ProcessExecutor($io);
+        if (0 !== $processExecutor->execute('git diff-files --quiet --ignore-submodules')) {
+            return false;
+        }
+
+        if (0 !== $processExecutor->execute('git diff-index --cached --quiet --ignore-submodules HEAD --')) {
+            return false;
+        }
+
+        return true;
+    }
 }