uniq(1) documentation

[Dan Jacobson]

Info 7.2 `uniq': Uniquify files:
      By default, `uniq' prints its input lines, except that it discards
   all but the first of adjacent repeated lines, so that no output lines
   are repeated.  Optionally, it can instead discard lines that are not
   repeated, or all repeated lines.
             ^^^^^^^^^^^^^^^^^^^^^^But that is what it does in the first place.

   `-D'
   `--all-repeated[=DELIMIT-METHOD]'
        Do not discard the second and subsequent repeated input lines, but
        discard lines that are not repeated.

Mention what if you want even the first of the repeated lines!

Man page:
       -d, --repeated
              only print duplicate lines
Say instead
              only print (the first of each group of) duplicate lines
Even if it is said on the Info page.