- start recording without the additional delay (required for creating the video file, setting up the raw backend, allocating memory etc)
- start recording with an additional remote
- group short bursts of action into a single clip
- interface with external triggers (using the half-shutter signals)
- interface with Lua scripts (using half-shutter - not tested, may require merging with lua_fix)
- interfacing with intervalometer or motion detection (not implemented, but very easy after this change)
The half-shutter triggers can be used as standalone, or alongside with pre-recording. Internally, they use the pre-recording backend to pause and resume the video (therefore skipping the frames that were not triggered).
The post-recording feature suggested by @mk11174 can be achieved in the "Half-shutter hold" mode, by holding the half-shutter as long as needed.
In all cases, you still have to press the usual REC button to start/stop a clip. Then, half-shutter (in the 3 different modes) should be used to start/pause recording.
The feature might be useful for the film scanning project from here as well: http://www.magiclantern.fm/forum/index.php?topic=19005
Test build available on http://builds.magiclantern.fm/experiments.html .