Add --saturnin-get-* for printing Saturnin internal info

src/shellfu/saturnin.sh

@@ -4,6 +4,31 @@ shellfu import exit
 shellfu import inigrep
 shellfu import pretty
 
+saturnin__get() {
+    #
+    # Show Saturnin Internal info by key $1 and exit
+    #
+    # Key $1 can be whole `--saturnin-get-stuff` argument or just
+    # the part after `--saturnin-get-`.
+    #
+    # This is aimed to help debugging and testing the app (or
+    # Saturnin itself) by showing packaging and deployment related
+    # info.
+    #
+    local key=${1#--saturnin-get-}
+    case "$key" in
+        shellfu-path)   echo "$SHELLFU_PATH"                ;;
+        inigrep-path)   echo "$SHELLFU_INIGREP_PATH"        ;;
+        app-version)    echo "$SATURNIN_APP_VERSION"        ;;
+        cache-home)     echo "$SATURNIN_CACHE_HOME"         ;;
+        libexec)        echo "$SATURNIN_LIBEXEC"            ;;
+        libexec-prefix) echo "$SATURNIN_LIBEXEC_PREFIX"     ;;
+        *)              warn "unknown devel key: $key"
+                        exit "$SHELLFU_EXIT_USAGE" ;;
+    esac
+    exit "$SHELLFU_EXIT_OK"
+}
+
 saturnin__help() {
     #
     # Print simple help message (basically just list of commands)
@@ -39,6 +64,7 @@ saturnin__main() {
         -v|--verbose)   export SHELLFU_VERBOSE=true; shift ;;
         --version)      saturnin__version; exit            ;;
         --version-semver) echo "$SATURNIN_APP_VERSION"; exit ;;
+        --saturnin-get-*) saturnin__get "$1" ;;
         -*)             saturnin__usage;                ;;
         --*)            saturnin__usage;                ;;
         --)             shift; break                    ;;