Unfortunately, `(f)` aka `(ps:\n:)` flag will not create an array when
there is only one line. The subsequent use of indexes will then affect
the string. This leads to `docker rmi <tab>` to complete on the header
line instead of nothing.
Therefore, for each use of `(f)`, we ensure that we have an extra new
line to be sure we get an array.
Credit to @povesteam for the original report and fix in #27373.
Signed-off-by: Vincent Bernat <vincent@bernat.im>
Upstream-commit: 38d93769fe
Component: cli
8871de5591