bug#25871: give plain join example first

[積丹尼 Dan Jacobson]

In (info "(coreutils) join invocation")

   If the input has no unpairable lines, a GNU extension is available;

(shouldn't that ";" be ":"?)


the sort order can be any order that considers two fields to be equal if
and only if the sort comparison described above considers them to be
equal.  For example:

     $ cat file1...

OK, but perhaps in the previous paragraph give a mundane regular
example of join usage, instead of the first example be this special
exception.