Nope, git can be initialized in directories with files in them.

  ➜  ~  mkdir test1
  ➜  ~  cd test1 
  ➜  test1  echo "hello" > hello.ttx
  ➜  test1  ls
  hello.ttx
  ➜  test1  git init
  Initialized empty Git repository in   /home/david/test1/.git/
  ➜  test1 git:(master) ✗ git status
  On branch master

  Initial commit

  Untracked files:
    (use "git add <file>..." to include in what will be committed)

  hello.ttx

  nothing added to commit but untracked files present (use "git add" to track)
  ➜  test1 git:(master) ✗