Add in_toolbox prompt to powerline themes

[Toolbox](https://github.com/containers/toolbox) is an containerized
development environment. This commit adds a promot to powerline when it
is running inside a toolbox.

themes/powerline/README.md

@@ -58,6 +58,7 @@ The contents of the prompt can be "reordered", all the "segments" (every piece o
 * `clock` - Current time in `HH:MM:SS` format
 * `cwd` - Current working directory including full folder hierarchy (c.f. `wd`)
 * `hostname` - Host name of machine
+* `in_toolbox` - Show identifier if running inside a toolbox
 * `in_vim` - Show identifier if running in `:terminal` from vim
 * `k8s_context` - Show current kubernetes context
 * `last_status` - Exit status of last run command

themes/powerline/powerline.base.bash

@@ -169,6 +169,12 @@ function __powerline_aws_profile_prompt() {
 	fi
 }
 
+function __powerline_in_toolbox_prompt() {
+	if [[ -e /run/.toolboxenv ]]; then
+		echo "${IN_TOOLBOX_THEME_PROMPT_TEXT}|${IN_TOOLBOX_THEME_PROMPT_COLOR}"
+	fi
+}
+
 function __powerline_shlvl_prompt() {
 	if [[ "${SHLVL}" -gt 1 ]]; then
 		local prompt="${SHLVL_THEME_PROMPT_CHAR}"

themes/powerline/powerline.theme.bash

@@ -71,6 +71,9 @@ THEME_CLOCK_FORMAT=${THEME_CLOCK_FORMAT:="%H:%M:%S"}
 IN_VIM_THEME_PROMPT_COLOR=${POWERLINE_IN_VIM_COLOR:=245}
 IN_VIM_THEME_PROMPT_TEXT=${POWERLINE_IN_VIM_TEXT:="vim"}
 
+IN_TOOLBOX_THEME_PROMPT_COLOR=${POWERLINE_IN_TOOLBOX_COLOR:=125}
+IN_TOOLBOX_THEME_PROMPT_TEXT=${POWERLINE_IN_TOOLBOX_TEXT:="❲T❳ "}
+
 HOST_THEME_PROMPT_COLOR=${POWERLINE_HOST_COLOR:=0}
 
 SHLVL_THEME_PROMPT_COLOR=${POWERLINE_SHLVL_COLOR:=${HOST_THEME_PROMPT_COLOR}}