Does git checkout update all files?

Question

Newb question, I want to make sure I understand this.

When I git checkout , does this return the entire project to its state at

Answer 1

When I git checkout , does this return the entire project to its state at that moment, or does it only recreate the files changed in that particular revision?

If your working tree and staging area are completely empty (besides the .git subdirectory, of course) and you run

git checkout 

then your working tree and staging area will perfectly reflect the contents of that particular revision.

On the other hand, if your working tree is not empty when you run git checkout, what happens is much more subtle, and may be broken down into three cases:

1. The checkout is not problematic and Git carries it out without batting an eyelid: the contents of that particular revision get copied to your working tree (and overwrite stuff already present there, if needed). Or
2. The checkout, if it were carried out, would result in a loss of local changes; therefore, Git (under the assumption that you didn't use the -f flag) tells you off and aborts the checkout. Or
3. A more complicated situation may arise in which stuff is only partially checked out, and some local, uncommitted changes are kept in your working tree and/or index. More details about that situation can be found in my answer to Why are unstaged changes still present after checking out a different branch?.

[...] the size of each checkout is varying quite a lot.

Are you taking into account untracked files? Did you commit, then later remove large files? On the basis of the information given in your question alone, we can do little more than hypothesize about the reason why the size varies a lot.