The staging area^W^Windex^Wcache is a terribly designed mess, that's why.
The best way to think about it is it's just a half-finished commit, i.e. one without a message and an author and a date. But otherwise git treats the index like any other commit. Adding stuff to the staging area is like amending that commit. Actually committing it is like amending that commit again, but without changing the files, only editing the metadata (message, author, etc). And then moving the current branch to it.
You could totally simulate the cache by doing exactly this, i.e. a series of `git commit -a --amend` commands (just make sure you don't push halfway). The idea behind the staging area is that you obviously need this all the time, because reasons, so let's force you to go through the hassle for every commit you might want to make.
Because it's just a commit that hates your guts, it has all the same side effects as making a real commit has.
> The idea behind the staging area is that you obviously need this all the time, because reasons, so let's force you to go through the hassle for every commit you might want to make.
I do need it all the time, and simulating it with commits would be horribly unsuited to getting work done. (The funny thing is that what you mentioned – `git commit -a` – doesn’t accomplish that, but it does skip the hassle you just said was forced.) It’s also a clean place to handle conflict resolution state, because that shouldn’t go in commits.
It does commit deletions. It doesn’t commit untracked files. If you really want to track every new file unprompted, an alias can be made for `git add --all && git commit`.
> The idea behind the staging area is that you obviously need this all the time
I have seen commits by people who habitually do `git commit -a`, and it has led me to the unavoidable conclusion that yes, you obviously need to stage commits all of the time.
The best way to think about it is it's just a half-finished commit, i.e. one without a message and an author and a date. But otherwise git treats the index like any other commit. Adding stuff to the staging area is like amending that commit. Actually committing it is like amending that commit again, but without changing the files, only editing the metadata (message, author, etc). And then moving the current branch to it.
You could totally simulate the cache by doing exactly this, i.e. a series of `git commit -a --amend` commands (just make sure you don't push halfway). The idea behind the staging area is that you obviously need this all the time, because reasons, so let's force you to go through the hassle for every commit you might want to make.
Because it's just a commit that hates your guts, it has all the same side effects as making a real commit has.