Adding jj information to the shell prompt

[!TIP] Fish shell users or Starship prompt users should review those pages instead as they have more specific advice. Note that Starship is a tool that supports multiple shell engines, including Bash and ZSH.

ZSH users can also use rkh/zsh-jj for vcs_info integration.

Some users like to have information about the current repository status printed out with every shell prompt. The following is example code that defines a shell function to check for the presence of a jj or Git repository, prints useful information about the repository, and adds the function to the PS1 prompt in bash or zsh.

# Dedicated to the Public Domain under the Unlicense: https://unlicense.org/UNLICENSE

# Print Git or jj repository information
jjgit_prompt()
{
  pwd_in_jjgit() # echo "jj" or "git" if either is found in $PWD or its parent directories
  { # using the shell is much faster than `git rev-parse --git-dir` or `jj root`
    local D="/$PWD"
    while test -n "$D" ; do
      test -e "$D/.jj" && { echo jj ; return; }
      test -e "$D/.git" && { echo git ; return; }
      D="${D%/*}"
    done
  }
  local jjgit="`pwd_in_jjgit`"  # results in "jj", "git" or ""
  if test "$jjgit" = jj ; then
    # --ignore-working-copy: avoid inspecting $PWD and concurrent snapshotting which could create divergent commits
    jj --ignore-working-copy --no-pager log --no-graph --color=always -r @ -T \
       ' "jj:[@ " ++ concat( separate(" ", format_short_change_id_with_hidden_and_divergent_info(self), format_short_commit_id(commit_id),
       				   bookmarks, if(conflict, label("conflict", "conflict")) ) ) ++ "]\n" ' 2>/dev/null
  elif test "$jjgit" = git ; then
    # --no-pager: never use a pager for the prompt, regardless of user config
    local gitprompt=$(git --no-pager log -1 --color=always
		      --pretty='%C(auto)%h ꜓%C(auto)%(decorate:prefix=,suffix=,tag=,pointer=→,separator= )' 2>/dev/null)
    echo "git:[${gitprompt/HEAD/}]"
  fi
}

# Add jjgit_prompt to PS1
test -n "$precmd_functions" && { # zsh
  ps1_jjgit_prompt() { PS1="`jjgit_prompt`"$'\n'"$PS1"; }
  precmd_functions=("${precmd_functions[@]/jjgit_prompt}") # remove old version
  precmd_functions+=(ps1_jjgit_prompt) # add new prompt function
} || { # bash
  [ $PS1 == *'$(jjgit_prompt)'* ](/jj-vcs/jj/wiki/-$PS1-==-*'$(jjgit_prompt)'*-) ||
    PS1='$(jjgit_prompt)\n'"$PS1"
}

To convert a Git repository into a jj repository, use jj git init --colocate.