alt Hacker NewsI agree, in a job where you have no documentation and no CI, and are working on something almost as old or older than you with ancient abandoned tools like svn that stopped being relevant 20 years ago, and in a fundamentally dysfunctional company/organization that hasn't bothered to move off of dead/dying tools in the last 20 years, then you just desperately grab at anything you can possibly find to try to avoid breaking things. But there are far better solutions to all of the problems you are mentioning than trying to make people create little mini feature commits on their way to a feature.
It is not possible to manually document everything down to individual lines of code. You'll drive yourself crazy trying to do so (and good luck getting anyone to look at that massive mess), and that's not even counting how documentation easily falls out of date. Meanwhile, we have "git blame" designed to do exactly that with almost no effort - just make good commit messages while the context is in your head.
CI also doesn't necessarily help here - you have to have tests for all possible edge cases committed from day one for it to prevent these situations. It may be a month or a year or several years later before you hit one of the weird cases no one thought about.
Calling svn part of the problem is also kind of backwards - it has no bearing on the code quality itself, but I brought it up because it was otherwise forcing good practice because it doesn't allow you to erase context that may be useful later.
Over the time I've been here we've migrated from Bugzilla to Fogbugz to Jira, from an internal wiki to ReadTheDocs to Confluence, and some of these hundreds of repos we manage started in cvs, not svn, and are now slowly being migrated to git. Guess what? The cvs->svn->git migrations are the only ones that didn't lose any data. None of the Bugzilla cases still exist and only a very small number were migrated from FogBugz to Jira. Some of the internal wiki was migrated directly to Confluence (and lost all formatting and internal links in the process), but ReadTheDocs are all gone. Commit messages are really the only thing you can actually rely on.