some linematch hunks need topdelete

[lewis6991]

Description

There are no signs for the bottom hunk since the modified position is taking its place.

[clktmr]

IMHO this should show a changedelete symbol on line 105. If there were another change after line 105 linematch would report 5 hunks (delete, change, delete, change, delete), in which case topdelete could be used for the last hunk, but the second delete would still have no sign.
I opened #954 which implements this. However the issue still exists that some hunks will not show up when show_preview is called. I think show_preview must check for multiple hunks on line to fix this.

[lewis6991]

If there were another change after line 105 linematch would report 5 hunks (delete, change, delete, change, delete), in which case topdelete could be used for the last hunk, but the second delete would still have no sign.

Yes, this is one edge case in which changedelete is still needed, however I still think topdelete should be preferred where is makes sense since it has a different highlight to change.