Merge pull request #512 from rodsouza9/master

Warning for git commit -a -m""

Author: ben

book/02-git-basics/sections/recording-changes.asc

@@ -466,6 +466,8 @@ $ git commit -a -m 'added new benchmarks'
 ----
 
 Notice how you don't have to run `git add` on the `CONTRIBUTING.md` file in this case before you commit.
+That's because the `-a` flag includes all changed files.
+This is convenient, but be careful; sometimes this flag will cause you to include unwanted changes.
 
 [[_removing_files]]
 ==== Removing Files