Nothing, but you have to do it right. If you look at Linux, you'll notice there is no central git server with a master branch that people push to. The most stab

Nothing, but you have to do it right. If you look at Linux, you'll notice there is no central git server with a master branch that people push to. The most stable development branch (in addition to the LTS branches), is whatever Linus Torvalds has chosen to merge to his personal master branch. He cuts a new release from there roughly every two months. Whatever is on that branch is the next version of Linux. That's integration branches done properly. Linux releases are cut from that branch. Literally everything else is an integration branch and it won't get pulled (you don't get to push) by Linus Torvalds until it merges cleanly and passes all the scrutiny that he and his people apply to incoming changes. Very few companies work like this of course. So instead you get people working on their pet branches and ignoring upstream changes. It's stupid. All you are doing is deferring integration work. Integration work scales exponentially relative tot he amount of change. So, the longer you wait, the worse it gets. The flip side is that having branches means you can distribute the integration work across those branches. And if each branch only has a small delta relative to the main branch, the collective integration work load decreases. The way you keep the delta small is by pulling upstream frequently and staying on top of the upstream changes. If you fall behind, it becomes a problem. And it's exclusively your problem. Linux doesn't have issues with integration work on the main branch: you are either compatible with upstream and ready to merge or you won't get pulled in. It's that simple. That's why Linus Torvalds can release a stable release regular as clock work. You don't get to stamp your feet and whine about how important your branch is. You do the integration work before your changes are pulled in and it's exclusively your problem to make that happen. So people, integrate upstream changes often and Linus keeps unstable changes out of upstream. They front load all the integration work before anyone even talks to Linus Torvalds. Done right, this scales to an ecosystem with thousands of contributors from a multitude of companies across the globe. It works by distributing the integration work across the ecosystem. This can work in large companies too. But you have to do it properly and with intent. Pull requests are pretty popular for a good reason: they work the same way. If you have to have long lived branches, somebody needs to worry about those staying in sync with upstream. If that doesn't happen, you have a problem waiting to happen.