bash 3.0 behaves differently ${x/find/replace} with %

[William Ballard <40711.nospam@comcast.net>]

Try this:

touch %

[run bash 2]
$ for x in %; do echo ${x/\%/a}; done
%a
$ for x in %; do echo ${x/\\%/a}; done
a

[run bash 3]
$ for x in %; do echo ${x/\%/a}; done
a
$ for x in %; do echo ${x/\\%/a}; done
%

Is this a bug?

I hit this bug because when I rename files downloaded into
/var/cache/apt/archives with an epoch, the : becomes %3a, and I
rename the files and remove that because for some reason it caused
some problem or other with my local archive if I didn't.

The difference is in bash 2 you needed \\% to match a % and in bash 3
you only need \%.  Is this "working as intended" or a bug?

I honestly have had a couple beers and the whole thing is pretty much a 
mystery to me.  Not wasting brain cycles on trivia like this.

Bug or intentional change?