Vim doesn’t show plugin documentation

vimvim-plugins

When I put a symbolic link to a .txt documentation plugin, vim doesn't show me the help

Example:
I have in ~/.vim/doc

 $ ls -al NERD_tree.txt 
 NERD_tree.txt -> PATH/nerdtree/doc/NERD_tree.txt

in vim:

:h NERDtree

This command doesn't show the documentation.

Vim needs to know when the help files are updated, so it can know where the NERDtree tag should point. Running the following in vim should fix it:

:helptags ~/.vim/doc

After installing a new help file into ~/.vim/doc, you need to rebuild the help tags file:

:helptags ~/.vim/doc

Then your :help rails command should work.

You don't need to do anything for Vim to find your plugins and settings. Except actually putting them in the right place.

On UNIX derivatives, $VIM refers to the directory where Vim's support files were installed. On Mac OS X, a UNIX derivative, Vim's default location is /usr/bin and its support files are installed in /usr/share.
Don't put your plugins/colorschemes/scripts in /usr/share/vim/vim73. Only default files should be there as they will likely be changed the next time you or Apple updates your install.
On Mac OS X (or any UNIX derivative) you must put your plugins/colorschemes/scripts in a ~/.vim directory and your custom settings in a ~/.vimrc file. None of these are there by default: you'll have to create them yourself as well as any needed sub-directories.
Some plugins consist of only one file, pluginname.vim that you should put in ~/.vim/plugin as in:
```
~/.vim/plugin/pluginname.vim
```
If the plugin and your version of Vim are compatible it should work. Check the plugin's page if it needs some activation command or setting. You'll need to relaunch Vim anyway.

Many plugins, though, are composed of many files in many directories like autoload, after, doc… You'll have to put the files in their corresponding directories under your ~/.vim, creating them as needed. Taking CtrlP as an example:
```
~/.vim/autoload/ctrlp/<many files>
~/.vim/autoload/ctrlp/ctrlp.vim
~/.vim/doc/ctrlp.txt
~/.vim/plugin/ctrlp.vim
```
Once you are OK with the basics of plugin management in Vim you should try Pathogen or Vundle or some other solution.