There may be others with different experiences, but in mine checking in half-finished code is a horrible idea, period.
Here are the principles I have learned and try to follow:
- Check in often - at least once, but preferably many times per day
- Only check in complete functionality
- If the first and second conflict (e.g. it takes more than a day to make the functionality work) then the task is too large - break it into smaller completable tasks.
This means:
- Commented-out code should never be checked in since it is not functional
- Commenting is not a valid archival strategy, so whether it's code yet-to-be-finished or code that's being retired, commenting and checking in doesn't make any sense.
So in summary, NO! If the code is not ready to go to the next stage (whichever that is for you: IntTest/QA/UAT/PreProd/Prod), it should not be committed to a trunk or multi-developer branch. Period.
Edit: After reading the other answers and comments, I'll add that I don't think it's necessarily a good idea to ban commented code (not sure how you'd enforce that anyway). What I will say is that you should get everyone on your team to buy in to the philosophy I described above. The team I work on embraces it wholeheartedly. As a result, source control is a frictonless team-member, one that helps us get our job done.
People who don't embrace that philosophy usually cause broken windows and are often frustrated by source control. They see it as a necessary evil at best, and something to avoid at worst; which leads to infrequent checkins, which means changesets are huge and hard to merge, which compounds frustration, makes checkins something to avoid even more, etc. This is ultimately an attitude thing, not really a process thing. It's easy to put up mental barriers against it; it's easy to find reasons why it won't work, just like it's easy to find reasons not to diet if you don't really want to. But when people do want to do it and are committed to changing their habits, the results are dramatic. The burden is on you to sell it effectively.
