Git.pm: stop assuming that absolute paths start with a slash

This fixes t7800 with MSys2.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

perl/Git.pm

@@ -188,7 +188,8 @@ sub repository {
 		};
 
 		if ($dir) {
-			$dir =~ m#^/# or $dir = $opts{Directory} . '/' . $dir;
+			_verify_require();
+			File::Spec->file_name_is_absolute($dir) or $dir = $opts{Directory} . '/' . $dir;
 			$opts{Repository} = abs_path($dir);
 
 			# If --git-dir went ok, this shouldn't die either.