Flatten an array of strings in Ruby

What's the best idiomatic (cleanest) way to convert an array of strings into a string, while keeping the enclosing quotes for each elements.
In other words, from this:

a = ["file 1.txt", "file 2.txt", "file 3.txt"]

I'd need to get this

"'file 1.txt' 'file 2.txt' 'file 3.txt'"

Single and double quotes could be interchanged here. The best ways I know of is by using map and inject/reduce.

eg: a.map{|dir| "'" + dir + "'"}.join(' ')
eg2: a.reduce("'"){|acc, dir| acc += dir+"' "}

Performance could be improved by avoiding temp string creation (+ operator). That's not my main question though. Is there a cleaner more concise way to achieve the same result?