count changes between commits for shell prompt?

[indirect]

I'm trying to set up a shell prompt for jj, and an area where I'm feeling stuck is figuring out how to count changes.

When using detached heads in git, I found it very helpful to have a short description pointing back to a known place. for example, if I’m 3 commits ahead of the (local) main branch, my shell status could say something like main~3. I’m trying to reproduce something similar via jj log, and I’m running up against the way that -T runs once per change in the revset, rather than running against a list of changes.

Is this really the easiest, shortest way to find out that I have three non-empty changes between@ and the local bookmark named main?

jj log --no-graph -r "main..@ & (~empty() | merges())" -T '"n"' 2> /dev/null | wc -c | tr -d ' '

[yuja]

Yes, I think it is the simplest way. There's no aggregate function/flag or template keyword to count distance from the latest bookmark/tag.

[shanesveller]

This might be a little similar in purpose/goal to #2563 as well, so you might find inspiration in the couple answers to that thread.