On the right side of the left panel there is a small empty bar. If a difference is shown, there is a small arrow on the left side of the right panel for copying from the right to left side. The corresponding arrow for copying from left to right is missing. If I click in the empty space on the left panel the copying from left to wright happens. Nevertheless the arrow is missing.
Probably a screenshot could help to understand better where is the problem. Anyway, please try this patch: https://git.gnome.org/browse/meld/patch/?id=35e959e0dd48956b9b6ca93a8bd5e80c91f79052 If it doesn't work, please report the issue directly to upstream (bugzilla.gnome.org) and paste the link here to let us track the issue
For me it's x11-libs/gtksourceview-3.18.3 that is causing the problem. All OK with gtksourceview-3.18.2. Lots of gutter changes in 3.18.3: https://git.gnome.org/browse/gtksourceview/log/?h=gnome-3-18 I've filed it as: https://bugzilla.gnome.org/show_bug.cgi?id=767085
Created attachment 435978 [details] screenshot with missing small arrow
OK, we are not going to stabilize that 3.18 gtksourceview bogus versions and, instead, we will jump to 3.20, that has this solved
