Add info bout reverting a cmmit

GIT.md

@@ -21,6 +21,12 @@ Then `git add <files>`to say you fix the conflict.
 
 Remove a specific commits: `git revert <commit id>`
 
+Revert
+======
+
+All the project `git revert <commit>`
+
+A specific file: `git checkout <commit> -- <paht/to/file>`
 
 Submodule
 =========