If I understand difference options for git add correctly, git add -u only adds modified and deleted files to the staging area, whereas git add . adds not only modified and deleted files but also untracked files. So I was wondering why we would ever wanna use git add -u when there's git add . or git add -A

CodePudding user response：

I use it a lot:

• If git status tells me that there are various modified files that are not staged for commit, and I want to add exactly those files, git add -u adds exactly those files without me having to think about it.

• If git status tells me that there are various modified files, and/or other files, where I don't want to en-masse add everything that git status mentioned, I run git diff and git diff --staged¹ if/as desired, git add individually, maybe an occasional git add -p, etc.

• If git status tells me that there are untracked files that I do want to add, I may use git add . (I use this rarely / sparingly so as to accidentally avoid adding files that should remain untracked; if git status shows untracked files that I don't want, I add them to an appropriate .gitignore first, but I still tend not to run git add ..)

Note that while git add -A will "add" a removal (and git add file-i-removed will do the same thing), my brain balks at this construct: I use git rm for it instead.

¹My fingers are wired to type this as git diff --cached, actually. These do exactly the same thing.

CodePudding user response：

Short form: it depends on your build/test cycle. If you generate a lot of detritus or other local-only work and it's easier to just step around it than manage it explicitly, git add -u makes it drop-dead easy to add only the stuff git already knows you care about.

Maybe you're generating something like UI-trace datasets to feed unit tests and have a lot of candidates, you explicitly add the ones worth tracking and use git add -u to apply any autogenerated updates (like say to keep the datasets current with changes to your trace driver).

Sure, you could make a "don't track these" directory and keep the not-ready-for-prime-time stuff in there, but that's more tedious than just using git add -u.