Instead of creating your Rails app from scratch, start with a prebuilt template.

GenericGem executes the bundle command but fills in important but easily forgotten details.

Insert the contents of the source file into the destination file. Look for a line with certain content in the destination file, and add the contents of the source file before or after this point. You can also look for two lines with certain content in the destination file and replace everything in between with the contents of the source file.