diff(1) Picks Different Lines with -u.

Hi,

[Please CC, I'm not subscribed.]

I found that `diff' and `diff -u' in diffutils 3.2 show a different
range of lines has changed.  1220a1221,1242 v. -1219,3 +1219,25.  The
former, no -u, shows an extra line has been added at the start of the
chunk compared with -u.  This puzzled me for a while but then I realised
the line repeats later in the file and -u shows it as the last line of
the added chunk.

It is reasonable to expect -u to only change the output format and not
which lines are reported as different?  When studying the diff in both
formats, as I was, it took a bit of head-scratching to understand the
apparent discrepancy.  I should be spending that effort on the diff
itself.  :-)

Cheers, Ralph.