All I am trying to say, it only makes sense to do/know effect analysis of your changes, before actually doing it. I fail to see, why they need to revert a piec

All I am trying to say, it only makes sense to do/know effect analysis of your changes, before actually doing it. I fail to see, why they need to revert a piece of code, and then realize, OMG... this version of code does not fit well with the rest of architecture, now change it back. 1.) I do not expect Google (or even a small shop, like my place) to revert any piece of code which is not affected. I, HOWEVER, expect to know what changes I am EXACTLY doing, and what to EXPECT after the changes. (It should not be black magic, for historical code). 2.) I fail to understand this, why should this the case for older code? I can understand some tricky/edge/minor cases, but whether the architecture/database etc. (major compatibility) is compatible or not, should be possible to calculate BEFORE doing the changes. I hope I am not over-trivializing the issue, but I still cannot get my head over the approach.