Study Git reset
1. Initial State
2. git reset --soft 8d553fd
Current file is represented at "Add text 'c'"
Staging area has commit about "Add text 'c'"
3. git reset --mixed 8d553fd
Current file is represented at "Add text 'c'"
"git reset --mixed" empty staging area
"add command" is canceled.
4. git reset --hard 8d553fd
Current file is represented at "Add text 'a'"
"git reset --mixed" empty staging area
"add command" is canceled.
++) Image reference about reset
