Add support for venvs

If you're in a venv, it shows the name in the prompt. Once I saw a cool
plugin that shows the python version, but that's got a heavy performance
overhead and I'd get annoyed looking at the same number every day.

For the new style to take effect, it expects you to have disabled your
normal venv PS1 by flag (`VIRTUAL_ENV_DISABLE_PROMPT`).

llama.zsh-theme

@@ -1,3 +1,5 @@
+#!/usr/bin/env zsh
+
 function llama_git_status {
   local unstaged_changes="$(git ls-files --others --modified --exclude-standard)"
   local staged_changes="$(git diff --name-only --cached)"
@@ -11,23 +13,60 @@ function llama_git_status {
   fi
 }
 
-function llama_branch_name {
-  local branch=$(git_current_branch)
-  local prompt=""
+function llama_venv_status {
+  if [[ -z "$VIRTUAL_ENV_DISABLE_PROMPT" ]]; then
+    return
+  fi
+
+  if [[ -z "$VIRTUAL_ENV" ]]; then
+    return
+  fi
+
+  title="%{$fg[cyan]%}$(basename "$VIRTUAL_ENV")"
+
+  if [[ ! -z "$1" ]]; then
+    title="%{$fg[yellow]%}($title%{$fg[yellow]%})"
+  fi
+
+  echo "$title"
+}
+
+function llama_branch_status {
+  local branch="$(git_current_branch)"
+
+  # It's a git repo.
+  if [[ ! -z "$branch" ]]; then
+    local prompt
+
+    prompt+=$(llama_git_status)
+    prompt+="%{$fg[cyan]%}$branch"
 
-  # Not a git repo.
-  if [[ -z "$branch" ]]; then
+    echo "$prompt"
+  fi
+}
+
+function llama_tool_summary {
+  local branch="$(llama_branch_status)"
+  local venv="$(llama_venv_status "$branch")"
+
+  if [[ -z "$branch" ]] && [[ -z "$venv" ]]; then
     echo " "
-    return 0
+    return
   fi
 
-  # Prettify the branch name.
-  prompt+="%{$fg[yellow]%}["
-  prompt+=$(llama_git_status)
-  prompt+="%{$fg[cyan]%}$branch"
-  prompt+="%{$fg[yellow]%}]"
+  local prompt
+  local delimiter=('[' ']')
+
+  if [[ -z "$branch" ]] && [[ ! -z "$venv" ]]; then
+    delimiter=('(' ')')
+  fi
 
-  echo $prompt
+  prompt+="%{$fg[yellow]%}${delimiter[1]}"
+  prompt+="$branch"
+  prompt+="$venv"
+  prompt+="%{$fg[yellow]%}${delimiter[2]}"
+
+  echo "$prompt"
 }
 
 function llama_return_status {
@@ -39,4 +78,13 @@ function llama_return_status {
   echo "${color}❯ %{$reset_color%}"
 }
 
-PROMPT='%{$fg[blue]%}%c$(llama_branch_name)$(llama_return_status)'
+function llama_prompt {
+  local prompt
+
+  prompt+="$(llama_tool_summary)"
+  prompt+="$(llama_return_status)"
+
+  echo "$prompt"
+}
+
+export PS1='%{$fg[blue]%}%c$(llama_prompt)'