Git Resets | DC Coding

I had a conversation with a colleague today about the git reset command.

I realised that while I use git reset --hard reasonably regularly (e.g. in order to move a branch when I've committed on the wrong one), I didn't know much about the --mixed or --soft modes.

The documentation on each of them is a little vague, so I thought I'd just try them out and see what happens. I hope this will serve as a useful reference.

Suppose I create a repository which looks as follows.

Initial Commit	Commit A	Commit B	Staged	Unstaged
`A1.txt` `A2.txt` `B1.txt` `B2.txt` `C1.txt` `C2.txt` `D1.txt` `D2.txt`	`A1.txt` `A2.txt` `A3.txt`	`B1.txt` `B2.txt` `B3.txt`	`C1.txt` `C2.txt` `C3.txt`	`D1.txt` `D2.txt` `D3.txt`

(Hopefully it's clear what I mean by each of these icons.)

Here's the result of performing different types of resets.

	Commit A	Commit B	Staged	Unstaged
Soft, commit B	`A1.txt` `A2.txt` `A3.txt`	`B1.txt` `B2.txt` `B3.txt`	`C1.txt` `C2.txt` `C3.txt`	`D1.txt` `D2.txt` `D3.txt`
Mixed, commit B	`A1.txt` `A2.txt` `A3.txt`	`B1.txt` `B2.txt` `B3.txt`		`C1.txt` `C2.txt` `C3.txt` `D1.txt` `D2.txt` `D3.txt`
Hard, commit B	`A1.txt` `A2.txt` `A3.txt`	`B1.txt` `B2.txt` `B3.txt`		`D3.txt`
Soft, commit A	`A1.txt` `A2.txt` `A3.txt`	N/A	`B1.txt` `B2.txt` `B3.txt` `C1.txt` `C2.txt` `C3.txt`	`D1.txt` `D2.txt` `D3.txt`
Mixed, commit A	`A1.txt` `A2.txt` `A3.txt`	N/A		`B1.txt` `B2.txt` `B3.txt` `C1.txt` `C2.txt` `C3.txt` `D1.txt` `D2.txt` `D3.txt`
Hard, commit A	`A1.txt` `A2.txt` `A3.txt`	N/A		`D3.txt`

The thing that surprised me most about this is what happens when you do a hard reset. Because the index only contains tracked files, the unstaged addition of D3.txt remains after the hard reset. Personally I think it would make more sense for Git to remove this file, but that's not what happens!