sid-isnt-done 0.2.0

#!/bin/sh
set -eu

# git_diff — show git diffs.
#
# Read-only wrapper around `git diff`.

lookup() {
    printenv "$1"
}

PREFIX=${RCVAR_ARGV0:?missing RCVAR_ARGV0}

case "${1:-}" in
rcvar)
    printf '%s\n' \
        "${PREFIX}_REQUEST_FILE" \
        "${PREFIX}_RESULT_FILE" \
        "${PREFIX}_SCRATCH_DIR" \
        "${PREFIX}_TEMP_DIR" \
        "${PREFIX}_TMPDIR" \
        "${PREFIX}_WORKSPACE_ROOT" \
        "${PREFIX}_SESSION_ID" \
        "${PREFIX}_SESSION_DIR" \
        "${PREFIX}_AGENT_ID" \
        "${PREFIX}_TOOL_ID" \
        "${PREFIX}_TOOL_NAME" \
        "${PREFIX}_TOOL_PROTOCOL" \
        "${PREFIX}_RC_CONF_PATH" \
        "${PREFIX}_RC_D_PATH"
    ;;
confirm)
    REQUEST_FILE="$(lookup "${PREFIX}_REQUEST_FILE")"
    staged=$(jq -r '.invocation.input.staged // false' "$REQUEST_FILE")
    ref=$(jq -r '.invocation.input.ref // empty' "$REQUEST_FILE")
    path=$(jq -r '.invocation.input.path // empty' "$REQUEST_FILE")
    desc="git diff"
    if [ "x$staged" = "xtrue" ]; then desc="${desc} --cached"; fi
    if [ -n "$ref" ]; then desc="${desc} ${ref}"; fi
    if [ -n "$path" ]; then desc="${desc} -- ${path}"; fi
    printf '%s\n' "$desc"
    ;;
run)
    REQUEST_FILE="$(lookup "${PREFIX}_REQUEST_FILE")"
    RESULT_FILE="$(lookup "${PREFIX}_RESULT_FILE")"
    WORKSPACE_ROOT="$(lookup "${PREFIX}_WORKSPACE_ROOT")"

    request_id=$(jq -r '.request_id' "$REQUEST_FILE")
    staged=$(jq -r '.invocation.input.staged // false' "$REQUEST_FILE")
    ref=$(jq -r '.invocation.input.ref // empty' "$REQUEST_FILE")
    path=$(jq -r '.invocation.input.path // empty' "$REQUEST_FILE")

    write_success() {
        text="$1"
        jq -n --arg rid "$request_id" --arg txt "$text" \
            '{"protocol_version":1,"request_id":$rid,"ok":true,"output":{"kind":"text","text":$txt},"error":null}' \
            > "$RESULT_FILE"
    }

    write_error() {
        code="$1"; msg="$2"
        jq -n --arg rid "$request_id" --arg c "$code" --arg m "$msg" \
            '{"protocol_version":1,"request_id":$rid,"ok":false,"output":null,"error":{"code":$c,"message":$m}}' \
            > "$RESULT_FILE"
    }

    cd "$WORKSPACE_ROOT"

    if ! git rev-parse --is-inside-work-tree >/dev/null 2>&1; then
        write_error "not_a_repo" "not a git repository: ${WORKSPACE_ROOT}"
        exit 0
    fi

    # Build git diff command
    git_args="diff"
    if [ "$staged" = "true" ]; then
        git_args="${git_args} --cached"
    fi
    if [ -n "$ref" ]; then
        git_args="${git_args} ${ref}"
    fi
    if [ -n "$path" ]; then
        git_args="${git_args} -- ${path}"
    fi

    output=$(git $git_args 2>&1) || true

    if [ -z "$output" ]; then
        write_success "No differences found."
    else
        write_success "$output"
    fi
    ;;
*)
    echo "usage: $0 [rcvar|confirm|run]" >&2
    exit 129
    ;;
esac