Proj2 Gitlet

/*
	*	.gitlet
	*		/--objects
	*		/	/--commits and blobs
	*		/--refs
	*		/	/--heads




	*/

No input args, print Please enter a command. and exit(System.exit(0))
Command not exist, print No command with that name exists. and exit
Command with wrong number or format of operands, Incorrect operands.
Command requires a initialized working directory but it's not, Not in an initialized Gitlet directory

add

Currently active pointer. We can switch the currently active head pointer with checkout [branch name]

So I will just. store branch information in HEAD file

Modified but not staged
- In current commit, changed but not staged(delete or modified)
- staged for addition but with different contents now
- staged for addition but deleted
Untracked files

java gitlet.Main checkout --[file name]
- replace the file in cwd with the head commit version
- file does not exist, No commit with that id exists
checkout [commit id] --[file name]
- replace the file in cwd with the given commit version
- no commit with that given id exists, No commit with that id exists
checkout [branch name]
- put all files in the commit of the head of branch in the pwd
- move HEAD
- delete files that are tracked in the current branch but not present in the updated branch
- clear stage?
- No branch with that name,No such branch exists.
- No need to checkout the current branch
- 文件名仅被Commit3B追踪的文件，而不被Commit3A追踪，那么直接将这些文件写入到工作目录。这里有个例外，即对于第三种情况，将要直接写入的时候如果有同名文件（例如1.txt）已经在工作目录中了，说明工作目录中在执行checkout前增加了新的1.txt文件而没有commit，这时候gitlet不知道是应该保存用户新添加进来的1.txt还是把Commit3B中的1.txt拿过来overwrite掉，为了避免出现信息丢失，gitlet就会报错，输出There is an untracked file in the way; delete it, or add and commit it first.