Idk which common Git commands you think are so incomprehensible or unstable between versions. Structure-wise, there's a combination of positional and non-positional arguments, but that's not uncommon on Linux. I haven't seen a major change in the way the Git UI works for the basics in the past decade, that I can recall. Of course Googling an answer to a problem can lead you off the beaten path, but I think that if you get an idea of what looks appropriate you won't be taken in by hairbrained approaches.
I think most of what you need is actually on this cheat sheet, so maybe all you needed was a reference.
Looking at subj cheatsheet, I immediately see `git add .` described as adding ALL untracked files and unstaged changes. But deleted files will not be included, unless you pass -A / --all. But wait, that's just my memories, since git now does include removed files, according to my tests today and https://git-scm.com/docs/git-add#Documentation/git-add.txt--.... It's hard to tell if that changed in the past decade or not, cause the manual never mentions neither a version not that -A is default now in a section corresponding to -A. I still have -A in my bash aliases and it was 2017 when I finally got frustrated enough to create them.
And this complexity was literally from the first trivial thing I checked, I wasn't looking for it for hours to gaslight anyone here. Git is nice and fast as a core program, but its ui, documentation, compat and informational ecosystem are just poor.
What do you mean, "deleted files" -- removed from the git staging area with "git rm", or actually deleted on the file-system level? (I don't think it ever added the latter, did it?)
I think most of what you need is actually on this cheat sheet, so maybe all you needed was a reference.