Add option to set another git repository

Setting another repository will generate a changelog for that repo.

README.md

@@ -28,6 +28,7 @@ new [issue](https://github.com/DigiLive/gitChangeLog/issues/new) is your concern
 
 ### Other
 
+- Set path to generate a changelog another local repository.
 - Set a From- and To tag to limit the changelog.
 - Filter subjects by labels<sup>1</sup>.
 - Set a header for the changelog (E.g. a title).

src/GitChangeLog.php

@@ -96,6 +96,10 @@ class GitChangeLog
      * @var string Format of a single commit hash. {hash} is replaced by the commit hash.
      */
     public $formatHash = '{hash}';
+    /**
+     * @var string Path to local git repository. Leave null for repository at current folder.
+     */
+    public $gitPath;
     /**
      * @var string Value of the oldest tag to include into the generated changelog.
      * @see GitChangeLog::setFromTag()
@@ -194,8 +198,11 @@ public function fetchTags($force = false): array
             return $this->gitTags;
         }
 
+        $gitPath = '--git-dir ';
+        $gitPath .= $this->gitPath ?? './.git';
+
         // Get all git tags.
-        $this->gitTags = explode("\n", shell_exec("git tag --sort=-{$this->options['tagOrderBy']}"));
+        $this->gitTags = explode("\n", shell_exec("git $gitPath tag --sort=-{$this->options['tagOrderBy']}"));
         array_pop($this->gitTags); // Remove empty element.
 
         $toKey = $this->toTag == 'HEAD' ? 0 : array_search($this->toTag, $this->gitTags);
@@ -342,22 +349,25 @@ public function fetchCommitData($force = false): array
             $gitTags[] = '';
         }
 
+        $gitPath = '--git-dir ';
+        $gitPath .= $this->gitPath ?? './.git';
+
         // Get tag dates and commit subjects from git log for each tag.
         foreach ($gitTags as $tag) {
             $tagRange            = $tag == '' ? $previousTag : "$tag...$previousTag";
             $includeMergeCommits = $this->options['includeMergeCommits'] ? '' : '--no-merges';
 
             $commitData[$previousTag]['date']     =
-                shell_exec("git log -1 --pretty=format:%ad --date=short $previousTag");
+                shell_exec("git $gitPath log -1 --pretty=format:%ad --date=short $previousTag");
             $commitData[$previousTag]['subjects'] =
                 explode(
                     "\n",
-                    shell_exec("git log $tagRange $includeMergeCommits --pretty=format:%s --reverse")
+                    shell_exec("git $gitPath log $tagRange $includeMergeCommits --pretty=format:%s --reverse")
                 );
             $commitData[$previousTag]['hashes']   =
                 explode(
                     "\n",
-                    shell_exec("git log $tagRange $includeMergeCommits --pretty=format:%h --reverse")
+                    shell_exec("git $gitPath log $tagRange $includeMergeCommits --pretty=format:%h --reverse")
                 );
             $previousTag                          = $tag;
         }