Today there is situation just for that, as Krzysztof Krawczyk has died.
TVP1 changed schedule and now broadcasting a documentary about him with a recital to follow. What I did is
ffmpeg -re -i (link to channel) Krawczyk.mp4
but it would be better have some built in solution
The developers are well aware of this limitation. Additionally, they have repeatedly stated that this situation is on their radar, and something they wish to address in the future. A quick search of the forum would bring up myriad posts about this same shortcoming, and the developers' acknowledgement.
(One additional note/rant: if you are using Ffmpeg to record a direct live stream, do not use the -re option in your command. That specific option is for use when streaming from a recorded file, and slows down the reading of the input file to real-time. When not using that option and reading from a saved file on disk, it can output data at a faster-than-live rate. In the case of using a real-time stream as your input, using this option is redundant, and may introduce errors, especially given how fickle some live broadcast streams can be.
Many third-party posts and tutorials involving Ffmpeg strewn across the internet repeat this same poor and incorrect advice. I really wish people would: 1) research and document their posts properly when providing commands, and 2) stop blindly copying-and-pasting commands from the internet into their computers without understanding what each option is for.</rant>)
Additionally, this topic was just discussed last week in reference to sporting event changes that are not reflected in the guide. I offered a workaround from within Channels itself for this similar circumstance. (The workaround does require some guide data for the channel, though. It will not work if there is no guide; but if the guide says "To be announced/determined", I believe this counts as guide data, and will work with the proffered idea.)
I remember your workaround but it's not suitable, because I didn't know when program going to end so I needed to ctrl-c manually anyway.
Ffmpeg has very complex and difficult manual, and there is no simple reading for simple situations that's why people including me often copy and paste code from stack overflow - because docs only tells you what -re flag is for, but not mention what you said post above. My experience is different because several times I encountered errors WITHOUT using -re so documentation and life are very different stories.
Most developers never taught children at school so they don't know how to write documentation and explain problem in simple terms unfortunately.
So it looks that I must increase pace of working on my ultimate channels dvr toolkit 
What I am missing is what is going under the hood, and it's difficult to write API endpoint that after request provide necessary actions for e.g. Tablo support mentioned in older thread.
currently I only managed to batch-processing commercial detection after cutting ads by using
curl -X PUT http://<ipadres>:8089/dvr/files/<FILE_ID>/recomskip
I don't expect endpoint for just video index regeneration 
So it looks
If you record the program before/during the event (such as: different guide data for a preempted program for a special), and add several hours of padding after, you can still achieve this within the Channels interface. Ctrl+C to cancel the recording isn't necessary, because you can stop a recording in progress from within the Channels interface at any point, and it will keep what has been recorded up until that point.
(The only problem with this is that the guide data/library entry would differ. But, that wouldn't really matter, because in your situation of recording from the command line, you have no guide data, and need to watch it outside of Channels, or try to match it with an import, which would still give you problems.)