NerdTree - Reveal file in tree

in :h NERDTree:

:NERDTreeFind                                                  :NERDTreeFind
    Find the current file in the tree. If no tree exists for the current tab,
    or the file is not under the current root, then initialize a new tree where
    the root is the directory of the current file.

I don't think it's bound to anything by default, so you have to do a keybind yourself.

nmap ,n :NERDTreeFind<CR>

is what appears in my .vimrc, along with

nmap ,m :NERDTreeToggle<CR>

This should also probably be just a comment. With the current version toggling NerdTree and using SyncTree causes NERDTree to be invoked twice. This modification seems to fix that problem:

" Check if NERDTree is open or active
function! IsNERDTreeOpen()
  return exists("t:NERDTreeBufName") && (bufwinnr(t:NERDTreeBufName) != -1)
endfunction

" Call NERDTreeFind iff NERDTree is active, current window contains a modifiable
" file, and we're not in vimdiff
function! SyncTree()
  if &modifiable && IsNERDTreeOpen() && strlen(expand('%')) > 0 && !&diff
    NERDTreeFind
    wincmd p
  endif
endfunction

" Highlight currently open buffer in NERDTree
autocmd BufEnter * call SyncTree()

function! ToggleNerdTree()
  set eventignore=BufEnter
  NERDTreeToggle
  set eventignore=
endfunction
nmap <C-n> :call ToggleNerdTree()<CR>

Check this out, it automates the sync operation, whenever you change buffer, the nerdtree will automatically refreshed itself (I copied from here with tiny modifications)

" Check if NERDTree is open or active
function! IsNERDTreeOpen()        
  return exists("t:NERDTreeBufName") && (bufwinnr(t:NERDTreeBufName) != -1)
endfunction

" Call NERDTreeFind iff NERDTree is active, current window contains a modifiable
" file, and we're not in vimdiff
function! SyncTree()
  if &modifiable && IsNERDTreeOpen() && strlen(expand('%')) > 0 && !&diff
    NERDTreeFind
    wincmd p
  endif
endfunction

" Highlight currently open buffer in NERDTree
autocmd BufEnter * call SyncTree()

Chen Rushan's answer + the comment worked perfectly well for me, except when the tree is open. With this setting, the current file in the tree will be revealed when the tree is opened.

" Check if NERDTree is open or active
function! IsNERDTreeOpen()
  return exists("t:NERDTreeBufName") && (bufwinnr(t:NERDTreeBufName) != -1)
endfunction

function! CheckIfCurrentBufferIsFile()
  return strlen(expand('%')) > 0
endfunction

" Call NERDTreeFind iff NERDTree is active, current window contains a modifiable
" file, and we're not in vimdiff
function! SyncTree()
  if &modifiable && IsNERDTreeOpen() && CheckIfCurrentBufferIsFile() && !&diff
    NERDTreeFind
    wincmd p
  endif
endfunction

" Highlight currently open buffer in NERDTree
autocmd BufRead * call SyncTree()

function! ToggleTree()
  if CheckIfCurrentBufferIsFile()
    if IsNERDTreeOpen()
      NERDTreeClose
    else
      NERDTreeFind
    endif
  else
    NERDTree
  endif
endfunction

" open NERDTree with ctrl + n
nmap <C-n> :call ToggleTree()<CR>