more robust self-update by using exec-spawned process

Author: holgerbrandl

kscript

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 ## note: always use a patch release even if it's 0
-KSCRIPT_VERSION=1.5.0
+KSCRIPT_VERSION=1.5.1
 
 ## make sure that all requirements (java, kotlinc, maven) to run kscript are met
 assertInPath(){ if [ -z "$(which $1)" ]; then echo "[ERROR] Could not locate '$1'" 1>&2; exit 1; fi }
@@ -94,12 +94,19 @@ if [[ "$1" == "--self-update" ]]; then
     ## choose update strategy depending on installation type
     if  [[ -z "$(which kscript | grep .sdkman)" ]]; then
         echo "Installing latest version of kscript..."
-        kurl https://git.io/v9R73 > $(which kscript) && chmod u+x $(which kscript)
+        kurl https://git.io/v9R73 > $(which kscript).tmp && chmod u+x $(which kscript).tmp
+        
+        # Create and spawn update script (see this may not work https://stackoverflow.com/questions/8595751/is-this-a-valid-self-update-approach-for-a-bash-script)
+cat > ${KSCRIPT_CACHE_DIR}/self_update.sh <<EOF
+mv "$(which kscript).tmp" "$(which kscript)"
+echo "You're now running kscript "$(kscript --help 2>&1| grep Version | cut -f2- | tr -d ':')
+EOF
+    exec /bin/bash ${KSCRIPT_CACHE_DIR}/self_update.sh
+
     else
         sdkman_auto_answer=true && sdk install kscript
     fi
 
-    echo "You're now running kscript "$(kscript --help 2>&1| grep Version | cut -f2- | tr -d ':')
     exit 0
 fi