git study: git add file:Add modification from workspace to stage.
git commit -m"commit": Commit modification from stage to branch.
git log:Show commits log from recent to farthest ("--pretty=oneline" argument can make information clear).
git reset --hard HEAD^:Rollback to particular version, "HEAD" means current version, "Head" followed by three "^" means the latest three versions. "HEAD~3" means the same.
<!-- git reset HEAD <file>: Unstage modification back to workspace. -->
git reflog:Show every command you do.
git status:Show status about every file in stage.
git restore <file>:Rollback file to last time you add or commit.
git restore --stage <file>:Unstage modification back to workspace.