Allow ghcup to be sourced

ghcup

@@ -43,7 +43,9 @@ VERSION=0.0.6
 
 # @VARIABLE: SCRIPT
 # @DESCRIPTION:
-# Name of this script.
+# Name of this script. This will be the
+# shell name if this script is sourced, so
+# only rely on this for echos and trivial things.
 SCRIPT="$(basename "$0")"
 
 # @VARIABLE: VERBOSE
@@ -905,6 +907,34 @@ posix_realpath() {
     unset mysource mydir posix_realpath_error
 }
 
+# @FUNCTION: is_sourced
+# @DESCRIPTION:
+# Tries to figure out if we are being sourced. Based on
+#   https://stackoverflow.com/a/28776166
+# @RETURNS: 0 if we are being sourced, 1 otherwise
+is_sourced() {
+    if [ -n "$ZSH_EVAL_CONTEXT" ]; then
+        case $ZSH_EVAL_CONTEXT in
+           *:file)
+               return 0 ;;
+       esac
+    elif [ -n "$KSH_VERSION" ]; then
+        # shellcheck disable=SC2154
+        [ "$(cd "$(dirname -- "$0")" && pwd -P)/$(basename -- "$0")" != "$(cd "$(dirname -- "${.sh.file}")" && pwd -P)/$(basename -- "${.sh.file}")" ] && return 0
+    elif [ -n "$BASH_VERSION" ]; then
+        # shellcheck disable=SC2128
+        [ "$0" != "$BASH_SOURCE" ] && return 0
+    else # All other shells: examine $0 for known shell binary filenames
+        # Detects `sh` and `dash`; add additional shell filenames as needed.
+        case ${0##*/} in
+            sh|dash)
+               return 0 ;;
+       esac
+   fi
+
+   # assume we are not sourced, if our above checks didn't find it
+   return 1
+}
 
 
 
@@ -1428,9 +1458,11 @@ if [ -z "$HOME" ] ; then
     die "HOME env not set, cannot operate"
 fi
 
-edo mkdir -p "${INSTALL_BASE}"
-edo mkdir -p "${BIN_LOCATION}"
-edo mkdir -p "${CACHE_LOCATION}"
+if ! is_sourced ; then
+    edo mkdir -p "${INSTALL_BASE}"
+    edo mkdir -p "${BIN_LOCATION}"
+    edo mkdir -p "${CACHE_LOCATION}"
+fi
 
 
 
@@ -1439,10 +1471,11 @@ edo mkdir -p "${CACHE_LOCATION}"
     #--[ Command line parsing and entry point ]--#
     ##############################################
 
+if ! is_sourced ; then
 
-[ $# -lt 1 ] && usage
+    [ $# -lt 1 ] && usage
 
-while [ $# -gt 0 ] ; do
+    while [ $# -gt 0 ] ; do
         case $1 in
         -v|--verbose)
             VERBOSE=true
@@ -1477,7 +1510,6 @@ while [ $# -gt 0 ] ; do
                command_exists "${com}" || die "Command \"${com}\" is required, but does not exist! Please install."
            done
            unset com
-
            case $1 in
            install)
                shift 1
@@ -1625,6 +1657,7 @@ while [ $# -gt 0 ] ; do
            esac
            break;;
         esac
-done
+    done
+fi # is_sourced
 
 # vim: tabstop=4 shiftwidth=4 expandtab