howto change location of .vimrc and .vim

Question

How can I change the location of the .vim folder and the .vimrc file so that I can use two (or more) independent versions of vim? Is there a way to configure that while compiling vim from source? (maybe an entry in the feature.h?)

Why do I want to do such a thing?: I have to work on project that use python2 as well as python3, therefore I want to have two independent vim setups with different plugins, configurations etc. Moreover, one version has to be compiled with +python, the other with +python3.

Answer 1

You can influence which ~/.vimrc is used via the -u vimrc-file command-line argument. Since this is the first initialization, you can then influence from where plugins are loaded (i.e. the .vim location) by modifying 'runtimepath' in there.

Note that for editing Python files of different versions, those settings (like indent, completion sources, etc.) are taken from filetype plugins which are sourced for every buffer separately, so it should be possible to even edit both Python 2 and 3 in the same Vim instance. (Unless you have some badly written plugins that define global stuff.) So for that, some sort of per-buffer configuration (some :autocmds on the project path, or some more elaborate solution (search for localrc plugins or questions about project vimrc here) might suffice already.

Also note that when the Python interpreter (which you'd only need for Python-based plugins and some interactive :py commands, not for editing Python) is compiled in with dynamic linking (which is the default at least on Windows), you can have both Python 2 and 3 support in the same Vim binary.

Answer 2

I found a way to do this! You can just create a fake $HOME, whose contents are simply the .vim folder and .vimrc. Then, when running vim, set the HOME environment variable to that folder, and change it back on VimEnter.

Run vim with:

OLD_HOME="$HOME" HOME="$FAKE_HOME" vim

Add this to your .vimrc:

autocmd VimEnter * let $HOME = $OLD_HOME

On Windows you can use

let $HOME = $HOMEDRIVE.$HOMEPATH

insetead, no need to store the old home.

This works, but if you use $HOME inside your vimrc or any plugins will see the old value, it might affect them somehow. So far I haven't seen it.