[Agnoster theme] Add the prompt view customization ability

[apodkutin]

By default prompt has these segments: prompt_status, prompt_context, prompt_virtualenv, prompt_dir, prompt_git, prompt_end in that particular order.

If you want to add, change the order or remove some segments of the prompt, you can use array environment variable named AGNOSTER_PROMPT.

Examples:

• Show all segments of the prompt with indices:

echo "${(F)AGNOSTER_PROMPT[@]}" | cat -n

• Add the new segment of the prompt to the beginning:

AGNOSTER_PROMPT=("prompt_git" "${AGNOSTER_PROMPT[@]}")

• Add the new segment of the prompt to the end:

AGNOSTER_PROMPT+="prompt_end"

• Insert the new segment of the prompt = PROMPT_SEGMENT_NAME on the particular position = PROMPT_SEGMENT_POSITION:

PROMPT_SEGMENT_POSITION=5 PROMPT_SEGMENT_NAME="prompt_end";\
AGNOSTER_PROMPT=("${AGNOSTER_PROMPT[@]:0:$PROMPT_SEGMENT_POSITION-1}" "$PROMPT_SEGMENT_NAME" "${AGNOSTER_PROMPT[@]:$PROMPT_SEGMENT_POSITION-1}");\
unset PROMPT_SEGMENT_POSITION PROMPT_SEGMENT_NAME

• Swap segments 4th and 5th:

SWAP_SEGMENTS=(4 5);\
TMP_VAR="$AGNOSTER_PROMPT[$SWAP_SEGMENTS[1]]"; AGNOSTER_PROMPT[$SWAP_SEGMENTS[1]]="$AGNOSTER_PROMPT[$SWAP_SEGMENTS[2]]"; AGNOSTER_PROMPT[$SWAP_SEGMENTS[2]]="$TMP_VAR"
unset SWAP_SEGMENTS TMP_VAR

• Remove the 5th segment:

AGNOSTER_PROMPT[5]=

A small demo of the dummy custom prompt segment, which has been created with help of the built-in prompt_segment() function from Agnoster theme:

# prompt_segment() - Takes two arguments, background and foreground.
# Both can be omitted, rendering default background/foreground.

customize_agnoster() {
  prompt_segment 'red' '' ' ⚙ ⚡⚡⚡ ⚙  '
}