updating notes on gitignoring file configurations

Author: rohan-paul

Git-and-Github/gitignore-file-configuration.md

@@ -50,3 +50,25 @@ node_modules/
 
 Source -  https://stackoverflow.com/a/1470664/1902852
 
+---
+
+### Important things to do after you change your .gitignore file and put new folder to the ignore list, which was already pushed to remote.
+
+If you already have a file checked in, and you want to ignore it, Git will not ignore the file if you add a rule later. In those cases, you must untrack the file first, by running the following command in your terminal:
+
+```
+git rm --cached
+
+```
+
+So if you want add to ignore some directories in your local repository (which already exist) after editing .gitignore you want to run this on your root dir
+
+```
+git rm --cached -r .
+git add .
+
+```
+It will basically 'refresh' your local repo and unstage ignored files.
+
+
+#### [Source](https://stackoverflow.com/a/30210030/1902852)