Multi-source copy -> full glyph paste -> edit layer confusion

[justvanrossum]

(Context: rcjk)

From @mrk-z:

if I create a new glyph by pasting something directly into the empty glyph, the default layer is called “foreground” instead of the default ““. Then in the new glyph, when I add a new axis and then a new source, the newly-added source is linked to the “foreground” source. So if I make edits in the new source it would change the “foreground” source too. I tried renaming the “foreground” layer to “default” or something else, and then adding the axis and a source. This seems to break this link and the glyph works fine

https://github.com/googlefonts/fontra/assets/4246121/35f37615-6e6c-4185-af13-d8fc24784f1b

What seems to be happening:

• The foreground layer is wrongly also in edit mode, but it doesn't show the pencil

So this seems to be a double bug:

1. the foreground layer shouldn't be in edit mode
2. but if it is, then the pencis should at least show

Additionally: when pasting, the layer name is used to create the source name (this explains the <default> vs foreground issue). Perhaps the source name should be kept. The naming should not cause the problem, but I can't rule out it is indeed involved.