Probably most people won't realise, but it was in that kind of situation that "continuous integration servers" came into being. The idea was that after you pushed to trunk, the tests would run (and in those days we slapped your fingers if the test suite ran for more than a minute or two -- for reasons which will become obvious) and you would have a minute or two to fix any gaffs you made merging conflicts, etc. If you wanted to merge your code, you would wait until the CI server gave a green light, so if the tests were slow, it would be a major PITA.
The massive upside of this process was that you always knew what your colleagues were planning to do. You saw all their progress every 20 minutes! You integrated with their changes! If you saw a problem, you yelled over the cubicle wall and said, "Hey that won't work because I'm doing X" -- saving both you and your colleague hours of wasted effort.
TBD in this style is hard, but very rewarding. The main reason I don't practice it these days is because 1) We have continuous deployment and you don't want to deploy unfinished work 2) The teams I work on these days are distributed (and I'm 9 timezone hours away from their day). However, I really miss that immediate feedback and the seemingly effortless way in which everyone on the team is kept completely in sync. I've never found anything that even comes close (and I've done the "preliminary PR" thing many times).