Is the Git staging area just an index?

Question

The book Pro Git says that the staging area is just a list, or index, that says which files will be committed when a git commit is done, and now the name inde

Answer 1

So how can the "staging area" keep track of what the first edit was if it is just an index -- a list?

An index is a list of names and pointers to content. In books, it's page numbers. In the Git index, it's object ID's in the repository's object database.

That's what the Git index is, a pathname-indexed list of content pointers.

git add for some pathname is basically

sha=`git hash-object -w path/to/it`
git update-index --cacheinfo 100644,$sha,path/to/it 

except git add checks for executable files and uses 100755 for those, and does recursive adds and checks your .gitignore and whatever else seems like it's usually most convenient. It's a convenience command for adding content to the object db and updating the index.