Add notice about not trying to allow path symlinks into source dir, refs #5974, refs #6174

src/Composer/Downloader/PathDownloader.php

@@ -46,6 +46,10 @@ class PathDownloader extends FileDownloader implements VcsCapableDownloaderInter
         }
 
         if (strpos(realpath($path) . DIRECTORY_SEPARATOR, $realUrl . DIRECTORY_SEPARATOR) === 0) {
+            // IMPORTANT NOTICE: If you wish to change this, don't. You are wasting your time and ours.
+            //
+            // Please see https://github.com/composer/composer/pull/5974 and https://github.com/composer/composer/pull/6174
+            // for previous attempts that were shut down because they did not work well enough or introduced too many risks.
             throw new \RuntimeException(sprintf(
                 'Package %s cannot install to "%s" inside its source at "%s"',
                 $package->getName(), realpath($path), $realUrl