Cut buffer does not persist between files

[Brian Zwahr]

I'm running into an issue that I'm not sure if it's a feature, a bug, or just 
an oversight. If I open a file in ed, yank some text with `y`, then open a new 
file for editing using `e`, I can't paste the yanked text with `x`. Example:

# Start with two files - test1 and test 2
# I want to copy the second line from test1 into test2
$ ed test1
25
# print the text stored in the file test1 with line numbers
,n
1 test1 text
2 a second line
# yank (copy) the second line of the file test1
2y
# open file test2 for editing
e test2
11
# attempt to paste the yanked text from test1 into test2
x
?
h
Nothing to put