fix wppm -p pkg[.] showing only the last extra, and make -p -l0 a true one-liner - #2059

The bug: commit 5114738 ("display missing dependancies") restructured down() in wppm/piptree.py so it could filter results for the new ! mode, but it moved the results += ... line outside the for one_extra in sorted(self.distro[p]["provides"]) loop. Each iteration overwrote a, and only the last extra in alphabetical order (xml for pandas) was appended to the output. It affected only -p with [.]; up() (-r) kept its accumulation inside the loop, which is why your reverse test was fine.

The fix: moved results += a if (len(a[0])>1 or ppend=="") else [] back inside the loop (and duplicated it in the else branch), at piptree.py:268-275.

One side note from the verification output: the ==? "missing dependency" lines show up even at -l0, since they're emitted at the current level rather than as a recursion — that's the new feature from 5114738 behaving as designed, just mentioning it in case you expected -l0 to stay one-line-per-extra.