zsh vcs_info integration for jj

This adds jj support to zsh's vcs_info. It's a bit quick-and-dirty but works for me.

vcs_info collects a few different values from the underlying version control system. This is how this integration maps them.

• action - divergent, hidden, conflict, empty, and/or root in a space-separated string
• branch - Local bookmarks, if any
• base - Unused
• staged - Unused
• unstaged - Unused
• revision - A string consisting of the jj change ID and the git commit hash, limited to 8 characters each and separated by a space. eg, qxospont 5d66059c
• misc - Unused

Using action for those values instead of misc is probably wrong, but it makes conditionalizing the display easier.

Installation

Place the VCS_INFO_detect_jj and VCS_INFO_get_data_jj files in your fpath.

Configuration

In your zshrc file, if you're using the git integration, you probably have a line like this:

zstyle ':vcs_info:*' enable git

Change that to:

zstyle ':vcs_info:*' enable jj git

Because jj repos are also git repos, it's very important that jj come before git in the list.

You can then configure your formats as you see fit. Personally, I have it configured like this:

zstyle ':vcs_info:jj:*' formats "%i" "%b"
zstyle ':vcs_info:jj:*' actionformats "%a|%i" "%b"

%a is the action value. %i is the revision value. %b is the branch value.

The two formats mean that the first value is placed into vcs_info_msg_0_ and the second value is placed into vcs_info_msg_1_.

In my precmd function, I have this:

psvar=()
[[ -n $vcs_info_msg_0_ ]] && print -v 'psvar[1]' -Pr -- "${vcs_info_msg_0_}"
[[ -n $vcs_info_msg_1_ ]] && print -v 'psvar[2]' -Pr -- "${vcs_info_msg_1_}"

And when I construct my prompt, I have something like this:

PROMPT="%m %~%(1v. (%1v%(2v. %2v.)).)%# "

The key part here is this chunk:

%(1v. (%1v%(2v. %2v.)).)

This is a nested conditional. %1v and %2v are the values that were placed into psvar[1] and psvar[2], respectively. If %1v is non-empty, it prints a space, open parenthesis, the %1v value, the %2v conditional, and the closing parenthesis. If %2v is non-empty, it prints a space and then its value.

So for something like an empty change, the prompt will look like this:

caisson ~/src/jj-zsh-vcs-info (empty|qxospont 5d66059c)%

And for a bookmark, it will look like this:

caisson ~/src/kia_uvo (mkltqqlm 7d9e3d04 services-yaml-update)%