Checkin release notes
Extended gutter theming support

The following four new keys have been added:

 - gutterIconsHover
 - gutterIconsPressed
 - gutterSelectionIconsHover
 - gutterSelectionIconsPressed
Move gutter styles to own settings dictionary

This removes all the blending, the need to provide a scope selector to obtain them, and no longer taxes the general syntax highlight (by no longer having to carry around a dozen gutter styles per scope).
Expose gutterSettings when editing themes

Also fix the grammar used for theme and macro editing (meta.plist → source.plist).
Allow cf::color_t to be uninitialized
No longer necessary to set all gutter colors

Previously all the colors were calculated so setting e.g. the icon color made it sort of necessary to also set the iconHover and iconPressed color.

Now the default icon hover and pressed colors are a potential user supplied icon color. Likewise, the default icon color is a potential user supplied foreground color, etc.
fixup! Retina assets for the "Bundle Editor" window

The non-retina bundle icon lost its alpha mask.
Remove ‘Template’ from image names

We don’t use them in a context where this property matters and we plan to convert them to image masks.
Increase folding image scale factor to 1.5
Change folding dots to be in image mask format

An image mask cannot use alpha but should instead be greyscale.
Add x- and cap height to metrics_t

This is to allow potential background bezels, images, and similar to be aligned with the text.
Add support for obtaining folding dots imagery

Also remove direct access to context_t’s member data (spelling dot image).
Use image for drawing folding dots

The color of the image can be set by adding a theme style for the foreground and scoped to “deco.folding”.
Use std::function as callback type for setup_timer

There is a minor functional change in that the custom callback type uses event loop signaling that makes it safe to trigger the callback from a thread. This should however not be necessary for timers (which are all setup on the main thread).
Use std::function with cf::callback_t
Treat gutter images as image masks

The advantage is that we avoid creating an off-screen image for compositing. We want to avoid off-screen images as they may not use the same pixel format/density as the render context (screen).
Gutter theming round-up

1. Removed the alpha channels from all images.
2. Deleted unnecessary double images. (@sorbits: You might want to
rename them to more accurately display what they do.)
3. Slight adjustments to improve the visibility of the bookmark icons
at lower font sizes.
No longer show dialog for readlink() failure

Only one readlink() failure reported (issue #389) which wouldn’t explain the crashes which the dialog (introduced in 68ed8293) was trying to track down.
Remove overwrite and freehanded toggles

Both from code and the menus. These were not implemented and I see no real reason to implement freehanded movement as a toggle since it is easily obtainable via column selections or option-clicking beyond EOL.

Overwrite mode might be implemented, but rather low priority.
Remove commented code

It’s unusable in its current state and it’s unclear what purpose the code would serve.