git 取消修改：修改了一些文件，可是並無commit

• This will unstage all files you might have staged with git add:

  git reset

• 撤消對文件的修改

• This will revert all local uncommitted changes (should be executed in repo root):

  git checkout .

  You can also revert uncommitted changes only to particular file or directory:

  git checkout [some_dir|file.txt]

  取消暫存的文件，能夠使用以下方法（指那些已經使用git add命令的）

• Yet another way to revert all uncommitted changes (longer to type, but works from any subdirectory):雖然在調用時加上 --hard 選項能夠令 git reset 成爲一個危險的命令（譯註：可能致使工做目錄中全部當前進度丟失！），但本例中工做目錄內的文件並不會被修改。 不加選項地調用git reset 並不危險 — 它只會修改暫存區域。

• git reset --hard HEAD

• This will remove all local untracked files, so only git tracked files remain:

  git clean -fdx

  WARNING: -x will also remove all ignored files!

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To sum it up: executing commands below is basically equivalent to fresh git clone from original source (but it does not re-download anything, so is much faster):

git reset
git checkout .
git clean -fdx

Typical usage for this would be in build scripts, when you must make sure that your tree is absolutely clean - does not have any modifications or locally created object files or build artefacts, and you want to make it work very fast and to not re-clone whole repository every single time.