bug#21880: Possible bug in sort --check --key

[Alexander Kindyakov]

Hello!

In sort man page nothing told about working sort --check with '--key' 
option. IMHO this behaviour is strange:

This case is succeeded:

 $ echo -e '1\t2\n1\t1' | LC_ALL=C sort --key=1b,1 --check --stable 
--field-separator=$'\t'

But this (without option '--stable') is failed:

$ echo -e '1\t2\n1\t1' | LC_ALL=C sort --key=1b,1 --check 
--field-separator=$'\t'
sort: -:2: disorder: 1  1

It seems to me both of situation is equal with relation of line key, why 
does the output is different?

Sincerely yours, Alexander K