Modify commands.walk to yield a 4-tuple.
The new element of the tuple indicates whether a name is an exact match
for one passed in on the command line.
*** 'a\nc\n\n\n\n' 'a\nb\n\n\n'
*** 'a\nb\nc\n' 'a\nc\n'
*** '' ''
*** 'a\nb\nc' 'a\nb\nc'
*** 'a\nb\nc\nd\n' 'a\nd\n'
*** 'a\nb\nc\nd\n' 'a\nc\ne\n'
*** 'a\nb\nc\n' 'a\nc\n'
*** 'a\n' 'c\na\nb\n'
*** 'a\n' ''
*** 'a\n' 'b\nc\n'
*** 'a\n' 'c\na\n'
*** '' 'adjfkjdjksdhfksj'
*** '' 'ab'
*** '' 'abc'
*** 'a' 'a'
*** 'ab' 'ab'
*** 'abc' 'abc'
*** 'a\n' 'a\n'
*** 'a\nb' 'a\nb'
done