常用的git add方法
git add <list-of-files> # add the list of files
git add --all # add all files
git add *.txt # add all files endswith ".txt" in current directory
git add docs/*.txt # add all files endswith ".txt" in docs directory
git add docs # add all files in docs directory
git add . # add current directory
git add "*.txt" # add all files endswith ".txt" in the whole project!