diff --git a/git_deploy.module b/git_deploy.module
index 61f66ee..731a5bd 100644
--- a/git_deploy.module
+++ b/git_deploy.module
@@ -21,32 +21,22 @@ define('GIT_DEPLOY_ERROR_DUMP', file_exists('/dev/null') ? '/dev/null' : 'nul');
 function git_deploy_system_info_alter(array &$info, Extension $file, $type) {
   static $projects = [];
   if ($file->origin == 'core' || empty($info['version'])) {
-    $directory = $file->getPath();
-    // Verify that this project was installed with Git.
-    while ($directory && !file_exists("$directory/.git")) {
-      $directory = substr($directory, 0, strrpos($directory, '/'));
-    }
-    $git_dir = (empty($directory) ? '' : "$directory/") . '.git';
-    // For core, finish verifying that it was installed with Git.
-    if (!empty($directory) || $file->origin == 'core' && file_exists($git_dir)) {
-      // Only check Git once per project.
-      $directory = $file->origin == 'core' ? 'core' : $directory;
+    // Make sure Git operates in the right directory.
+    chdir($file->getPath());
+    // Verify that we are in a Git repository.
+    $directory = exec('git rev-parse --show-toplevel 2> ' . GIT_DEPLOY_ERROR_DUMP);
+    if (!empty($directory)) {
+      // Only check Git once per repository.
       if (!isset($projects[$directory])) {
         $projects[$directory] = [];
-        // Make sure Git operates in the right directory.
-        $git = "git --git-dir $git_dir";
         // Get upstream info.
         list($core) = explode('.', $info['core']);
-        $upstream = _git_deploy_get_upstream($git, $file->origin == 'core' ? "$core*" : "$info[core]-*");
+        $upstream = _git_deploy_get_upstream($file->origin == 'core' ? "$core*" : "$info[core]-*");
         // Find the project name based on fetch URL.
         if (isset($upstream['remote'])) {
-          $fetch_url = exec("$git config --get remote.$upstream[remote].url 2> " . GIT_DEPLOY_ERROR_DUMP);
+          $fetch_url = exec("git config --get remote.$upstream[remote].url 2> " . GIT_DEPLOY_ERROR_DUMP);
           if (!empty($fetch_url)) {
-            $project_name = substr($fetch_url, strrpos($fetch_url, '/') + 1);
-            if (substr($project_name, -4) == '.git') {
-              $project_name = substr($project_name, 0, -4);
-            }
-            $projects[$directory]['project'] = $project_name;
+            $projects[$directory]['project'] = basename($fetch_url, '.git');
           }
         }
         // Set version from tag.
@@ -64,14 +54,16 @@ function git_deploy_system_info_alter(array &$info, Extension $file, $type) {
       }
       $info = $projects[$directory] + $info;
     }
+    // Switch back to Drupal root folder.
+    chdir(DRUPAL_ROOT);
   }
 }
 
 /**
  * Gets upstream info.
  *
- * @param string $git
- *   Git formatted for command line.
+ * This function must be run from within a Git repository.
+ *
  * @param string $pattern
  *   Pattern for matching branch names, without trailing ".x". Must not include
  *   remote. Also used to check for release tags.
@@ -83,49 +75,49 @@ function git_deploy_system_info_alter(array &$info, Extension $file, $type) {
  *   - tag: Release tag from last common commit in matching branch.
  *   - datestamp: Unix timestamp of last common commit.
  */
-function _git_deploy_get_upstream($git, $pattern = '*') {
+function _git_deploy_get_upstream($pattern = '*') {
   $upstream = [];
   // Get tracked upstream branch.
-  $remote = exec("$git rev-parse --abbrev-ref @{upstream} 2> " . GIT_DEPLOY_ERROR_DUMP);
+  $remote = exec('git rev-parse --abbrev-ref @{upstream} 2> ' . GIT_DEPLOY_ERROR_DUMP);
   if (fnmatch("*/$pattern.x", $remote)) {
     // Set remote.
     list($upstream['branch'], $upstream['remote']) = array_reverse(explode('/', $remote));
     // Find last common commit in both local and upstream.
-    $last_base = exec("$git merge-base HEAD $remote 2> " . GIT_DEPLOY_ERROR_DUMP);
+    $last_base = exec("git merge-base HEAD $remote 2> " . GIT_DEPLOY_ERROR_DUMP);
     // Get time of last common commit.
-    $upstream['datestamp'] = exec("$git log -1 --pretty=format:%at $last_base 2> " . GIT_DEPLOY_ERROR_DUMP);
+    $upstream['datestamp'] = exec("git log -1 --pretty=format:%at $last_base 2> " . GIT_DEPLOY_ERROR_DUMP);
   }
   else {
     // If local does not track an upstream branch, find best matching remote
     // branch.
-    exec("$git remote 2> " . GIT_DEPLOY_ERROR_DUMP, $remotes);
+    exec('git remote 2> ' . GIT_DEPLOY_ERROR_DUMP, $remotes);
     if (!empty($remotes)) {
       // Only consider the origin remote, if it exists.
       $branch_pattern = in_array('origin', $remotes) ? "origin/$pattern.x" : "*/$pattern.x";
       // List matching branches in descending order.
-      exec("$git branch -r --sort=-refname --list --format='%(refname:short)' $branch_pattern 2> " . GIT_DEPLOY_ERROR_DUMP, $branches);
+      exec("git branch -r --sort=-refname --list --format='%(refname:short)' $branch_pattern 2> " . GIT_DEPLOY_ERROR_DUMP, $branches);
       if (!empty($branches)) {
         $remote = array_shift($branches);
         // Find last common commit in both local and upstream.
-        $last_base = exec("$git merge-base HEAD $remote 2> " . GIT_DEPLOY_ERROR_DUMP);
+        $last_base = exec("git merge-base HEAD $remote 2> " . GIT_DEPLOY_ERROR_DUMP);
         if (!empty($branches)) {
           // There's no reason to check other branches for a more recent common
           // commit if they do not contain the base commit, so filter the branch
           // list.
-          exec("$git branch -r --sort=-refname --contains $last_base --no-contains $remote --format='%(refname:short)' $branch_pattern 2> " . GIT_DEPLOY_ERROR_DUMP, $branches);
+          exec("git branch -r --sort=-refname --contains $last_base --no-contains $remote --format='%(refname:short)' $branch_pattern 2> " . GIT_DEPLOY_ERROR_DUMP, $branches);
           while (!empty($branches)) {
             $branch = array_shift($branches);
             // Find last common commit in both local and upstream.
-            $base = exec("$git merge-base HEAD $branch 2> " . GIT_DEPLOY_ERROR_DUMP);
+            $base = exec("git merge-base HEAD $branch 2> " . GIT_DEPLOY_ERROR_DUMP);
             // Count commits since last base commit.
-            $difference = exec("$git rev-list --count $base ^$last_base 2> " . GIT_DEPLOY_ERROR_DUMP);
+            $difference = exec("git rev-list --count $base ^$last_base 2> " . GIT_DEPLOY_ERROR_DUMP);
             // If base contains new commits, it is a better match.
             if (!empty($difference)) {
               $remote = $branch;
               $last_base = $base;
               if (!empty($branches)) {
                 // Filter the branch list.
-                exec("$git branch -r --sort=-refname --contains $last_base --no-contains $remote --format='%(refname:short)' $branch_pattern 2> " . GIT_DEPLOY_ERROR_DUMP, $branches);
+                exec("git branch -r --sort=-refname --contains $last_base --no-contains $remote --format='%(refname:short)' $branch_pattern 2> " . GIT_DEPLOY_ERROR_DUMP, $branches);
               }
             }
           }
@@ -133,13 +125,13 @@ function _git_deploy_get_upstream($git, $pattern = '*') {
         // Set remote.
         list($upstream['branch'], $upstream['remote']) = array_reverse(explode('/', $remote));
         // Check for latest release tag from last common commit.
-        exec("$git tag --points-at $last_base $pattern.* 2> " . GIT_DEPLOY_ERROR_DUMP, $tags);
+        exec("git tag --points-at $last_base $pattern.* 2> " . GIT_DEPLOY_ERROR_DUMP, $tags);
         if (!empty($tags)) {
           usort($tags, 'version_compare');
           $upstream['tag'] = end($tags);
         }
         // Get time of last common commit.
-        $upstream['datestamp'] = exec("$git log -1 --pretty=format:%at $last_base 2> " . GIT_DEPLOY_ERROR_DUMP);
+        $upstream['datestamp'] = exec("git log -1 --pretty=format:%at $last_base 2> " . GIT_DEPLOY_ERROR_DUMP);
       }
     }
   }
@@ -153,23 +145,20 @@ function git_deploy_update_status_alter(&$projects) {
   foreach ($projects as $project => &$project_info) {
     // Override the update status on dev branches.
     if ($project_info['install_type'] == 'dev' && in_array($project_info['status'], [UpdateManagerInterface::NOT_SECURE, UpdateManagerInterface::NOT_CURRENT])) {
-      $directory = drupal_get_path(preg_replace('/-disabled$/', '', $project_info['project_type']), key($project_info['includes']));
-      // Verify that this project was installed with Git.
-      while ($directory && !file_exists("$directory/.git")) {
-        $directory = substr($directory, 0,  strrpos($directory, '/'));
-      }
-      $git_dir = (empty($directory) ? '' : "$directory/") . '.git';
-      if (!empty($directory) || $project_info['project_type'] == 'core' && file_exists($git_dir)) {
+      // Make sure Git operates in the right directory.
+      chdir(drupal_get_path(preg_replace('/-disabled$/', '', $project_info['project_type']), key($project_info['includes'])));
+      // Verify that we are in a Git repository.
+      $directory = exec('git rev-parse --show-toplevel 2> ' . GIT_DEPLOY_ERROR_DUMP);
+      if (!empty($directory)) {
         $version = $project_info['existing_version'];
         if (isset($project_info['releases'][$version])) {
           $release = $project_info['releases'][$version];
           if (isset($release['tag'])) {
-            $git = "git --git-dir $git_dir";
             // Fetch latest commit from origin.
-            exec("$git fetch origin 2> " . GIT_DEPLOY_ERROR_DUMP);
-            $last_commit = exec("$git log -1 --pretty=format:%H origin/$release[tag] 2> " . GIT_DEPLOY_ERROR_DUMP);
+            exec('git fetch origin 2> ' . GIT_DEPLOY_ERROR_DUMP);
+            $last_commit = exec("git log -1 --pretty=format:%H origin/$release[tag] 2> " . GIT_DEPLOY_ERROR_DUMP);
             // See if local branch contains latest commit.
-            exec("$git merge-base --is-ancestor $last_commit HEAD 2> " . GIT_DEPLOY_ERROR_DUMP, $output, $return_val);
+            exec("git merge-base --is-ancestor $last_commit HEAD 2> " . GIT_DEPLOY_ERROR_DUMP, $output, $return_val);
             // We still need to compare commit time to release time because this
             // repository may have been cloned from a copy of the upstream
             // repository. Allow a 12 hour time difference between release and
@@ -183,4 +172,6 @@ function git_deploy_update_status_alter(&$projects) {
       }
     }
   }
+  // Switch back to Drupal root folder.
+  chdir(DRUPAL_ROOT);
 }