termcwd for Vim

This plugin for command-line Vim makes Apple Terminal's proxy icon reflect Vim's current file (for windows that have one) or working directory (for most other windows).

It works by using escape sequences to send Vim's current file and working directory to Terminal. Depending on Terminal's configuration, this may also affect the titles and initial working directories of its windows and tabs [1].

This software is released as open source using the MIT (i.e., Expat) License.

Requirements

Vim 7.2 or later with the +autocmd, +eval, and +modify_fname features. This can be checked with Vim's :version command or by running vim --version in a shell [2].

Earlier versions may work, but 7.2 is my baseline. A few behaviors do require newer Vim patches.
- Patch 8.0.1459 allows updating Terminal immediately after Vim's working directory changes [3].
- Patch 8.0.1596 allows updating Terminal when entering a Vim terminal window for the first time [3].
- Patch 8.2.2128 allows updating Terminal before Vim is suspended [4] and immediately after Vim resumes [3].
Apple Terminal from Mac OS X Lion 10.7 or later — i.e., version 2.2.3 (303.2) or later. This can be checked from Terminal by choosing "About Terminal" from the "Terminal" menu.

Installation

This plugin has nothing to configure, so just download it and make sure Vim can find it at startup. Here are a few options:

Clone this repository into a Vim package. Recommended for Vim 8 or later.

mkdir -p ~/.vim/pack/whatever/start \
    && cd ~/.vim/pack/whatever/start \
    && git clone https://github.com/larryv/termcwd-vim.git

Use a third-party plugin manager such as Tim Pope's pathogen. Its documentation should explain how to install plugins. Recommended for Vim 7, which predates native package support.
Clone or download this repository to an arbitrary location and manually update Vim's runtimepath option (perhaps in ~/.vimrc). Left as an exercise for the reader. Recommended for my enemies.

That's it. Enjoy the icon.

Notes

[1]	Terminal's General preferences determine whether new windows or tabs open with the same working directory as the current window or tab. Each profile's Window and Tab preferences determine whether windows' and tabs' titles display the name or path of the working document or directory.

[2]	Do not simply look at Vim's welcome screen, as it does not provide complete version information. For example, in the system Vim on macOS Mojave 10.14.6 it says "version 8.0.1365", but `:version` says "8.0 […] Included patches: 1-503, 505-680, 682-1283, 1365".

[3]	(1, 2, 3) Even without these patches, Terminal is updated as soon as the user switches Vim windows or buffers.

[4]	Without this patch, Terminal's state becomes stale when Vim is suspended, unless the subsequent process updates it.