Updating to rails 2 2 2
And in the process, you’ll learn how to take full advantage of Rails 4.2’s new features.You should always start your Rails upgrade by reading the Rails Upgrade Guide.I searched Git Hub and people had already patched them.
Resolving all dependencies from scratch can have surprising results, especially if a number of the third-party packages you depend on have released new versions since you last did a full update.
If nothing else, it’ll motivate you to get that upgrade done.
When you’re moving to a new Rails version, always upgrade to the newest point version first. So if you want to upgrade from 4.1.6 to 4.2, go 4.1.6 to 4.1.9, and 4.1.9 to 4.2.
To illustrate, the probably won't break anything, similar scenarios can happen that involve much larger jumps.
(see  below for a larger discussion) In order to avoid this problem, when you update a gem, bundler will not update a dependency of that gem if another gem still depends on it. If bundler needs to update a gem that another gem depends on, it will let you know after the update has completed.