diff --git a/creation_repo.sh b/creation_repo.sh
index d7cdec3..346a792 100755
--- a/creation_repo.sh
+++ b/creation_repo.sh
@@ -19,10 +19,10 @@ create_random_file(){
     dd if=/dev/urandom of=$1 bs=$2 count=1 &> /dev/null
 }
 
-REPO_NAME=performance_testing
+REPO_NAME=git_update_testing
 REPO_PATH=./remote
 WITH_SUBMODULE="false"
-SUB_NAME="submodule_for_performance_testing"
+SUB_NAME="submodule"
 WITH_LINK="false"
 while getopts ":hn:sl:" option; do
    case $option in
@@ -84,7 +84,7 @@ if [ ! -d $REPO_NAME ]; then
         git add .
         git commit -m"first 1M sample created"
         cd ../$REPO_NAME
-        git submodule add ../submodule_for_performance_testing
+        git submodule add ../$SUB_NAME
         git commit -am "adding $SUB_NAME module"
     fi
     cd ..
@@ -99,7 +99,7 @@ else # $REPO_NAME exists
         git add .
         git commit -m"first 1M sample created"
         cd ../$REPO_NAME
-        git submodule add ../submodule_for_performance_testing
+        git submodule add ../$SUB_NAME
         git commit -am "adding $SUB_NAME module"
     elif [[ "$WITH_SUBMODULE" != "true" && -d $SUB_NAME ]]; then
         cd $REPO_NAME
diff --git a/git_update.sh b/git_update.sh
index c60834c..2056059 100755
--- a/git_update.sh
+++ b/git_update.sh
@@ -1,46 +1,43 @@
 #!/bin/bash
-summary="$0 [options] <repo>"
-ref=main
-dst='.'
-nonempty_target=false
-use_home=false
-be_aggressive=false
-
 Help(){
 	echo "
 NAME
     git_update.sh
 SYNOPSIS
-    git_update.sh [-h] [-r ref] [-d dest] [-H] [-N] [-a] repository
+    git_update.sh [-h] [-r ref] [-d dest] [-H] [-a] repository
 OPTIONS
-    -h prints the help. 
+	-h prints the help. 
 	-r specifies the reference to the commit to be synchronized. It can be a tag or a branch. By default, it is the last commit of branch main.
-	-d specifies the destination of the clone or update. If non-empty, -N must be specified. 
-	-H 
-	-N indicates that the destination is non-empty. The files that do not conflict and if it is an update, are not committed, will be kept. 
-	-a specifies that the aggressive option of git clean must be used. git clean is called wen -N is not specified. 
+	-d specifies the destination of the clone or update. Directory must be empty if a new clone is to be made.
 	If the repository to be cloned is local, and its path is passed as a relative path, the path should start from the destination. 
-	To avoid mistakes, absolute paths are advised.
-
+	To avoid mistakes, absolute paths are advised. 
+	-H allows the $HOME directory to be used by git_update.sh. By default, git_update.sh cannot access $HOME to prevent default behavior. 
+	If you need the global .gitconfig located in your $HOME to be used, you should supply the -H option. 	
+	-a specifies that the aggressive option of the git garbage collection must be used. Only advised when changes happen in many different objects. Will slow down the execution.   
 DESCRIPTION
-	This script will replace the destination with the wanted commit of a git repository. The history is not preserved but tags are.
+	This script will replace the destination with the wanted commit of a git repository. The history is not preserved but tags are. Untracked files remain.
 	The git commands have been chosen so as to minimize the memory and bandwidth usages."
 }
 
-while getopts ":hr:d:NHa" option; do
+#variables
+summary="$0 [options] <repo>"
+ref=main
+dst='.'
+use_home=false
+be_aggressive="false"
+
+while getopts ":hr:d:H" option; do
    case $option in
       h) # display Help
          Help
          exit;;
-      r) # branch or tag wanted
+      r) # desired branch or tag 
             ref="$OPTARG";;
       d) # destination of clone
             dst="$OPTARG";; 
-	  N) # clone to a Non-empty target. Existing files will be overwritten
-	  		nonempty_target="true";;
 	  H) # use real home dir
-	  		use_home="false";;
-	  a) # use git clean with the aggressive option
+	  		use_home="true";;
+	  a) #use -a in git gc call 
 	  		be_aggressive="true";;
      \?) # invalid option
          echo "Error: Invalid option here"
@@ -49,7 +46,6 @@ while getopts ":hr:d:NHa" option; do
 done
 shift $((OPTIND-1))
 
-
 repo="$1"
 if [ -z "$repo" ] ; then
 	exit "$0: Empty repo given\n$summary"
@@ -64,36 +60,21 @@ fi
 mkdir -p "$dst"
 cd "$dst"
 
-
 if [ -d .git ] ; then
-
-	git submodule update --init --recursive --force --depth=1 --remote 
+	echo "updating..."
 	git fetch --tags --depth=1 --prune --prune-tags --force origin $ref 
-	git reset --hard FETCH_HEAD 
+	git reset --hard --recurse-submodules FETCH_HEAD 
+	git submodule update --init --recursive --force --depth=1 --remote 
+	#garbage collection of anything unreachable at the moment
 	git reflog expire --expire=now --all 
 	if "$be_aggressive" ; then
 		git gc --prune=now --aggressive
-	else
+	elsels
 		git gc --prune=now 
 	fi
-	# Preserve existing files in some cases
-	if ! "$nonempty_target" ; then #we keep uncommitted files when in -N mode
-		git clean -qfdx
-	fi
-
 else
+echo "cloning..."
 	clone_dst='.'
-
-	# To override an existing dir, we need to clone elsewhere first
-	if "$nonempty_target" ; then
-		clone_dst="$(mktemp -d)"
-	fi
     git clone -b "$ref" --recurse-submodules --shallow-submodules --depth 1 "$repo" "$clone_dst" 
-
-	# To override an existing dir, we then move everything to that dir
-	if "$nonempty_target" ; then
-		mv "$clone_dst/"{*,.*} .
-		rmdir "$clone_dst"
-	fi
 fi
 
diff --git a/test_git_update.sh b/test_git_update.sh
index eab0f60..eccedbc 100755
--- a/test_git_update.sh
+++ b/test_git_update.sh
@@ -24,15 +24,17 @@ DESCRIPTION
     TEST6: git updated, switching to another branch, deleting and adding files in the process
     TEST7: git updated, switching to a tag, deleting and adding files in the process
     TEST8: git updated, before and after changing a tag, deleting and adding files in the process
+    TEST9: git updated fast-forward on submodule on main 
 "
 }
 
 #Variables definitions
 WORKING_DIRECTORY=$(pwd)
-REMOTE="file://${WORKING_DIRECTORY}/remote/git_update_testing" #we must trick git_update.sh into thinking we are not working in local, otherwise depth=1 is not respected
-LOCAL_REMOTE="/${WORKING_DIRECTORY}/remote/git_update_testing" #cd does not understand file://
 REPO_NAME="git_update_testing"
-WITH_SUBMODULE="true"
+SUBMODULE_NAME="submodule"
+REMOTE="file://${WORKING_DIRECTORY}/remote/$REPO_NAME" #we must trick git_update.sh into thinking we are not working in local, otherwise depth=1 is not respected
+LOCAL_REMOTE="/${WORKING_DIRECTORY}/remote/$REPO_NAME" #cd does not understand file://
+LOCAL_REMOTE_SUBMODULE="/${WORKING_DIRECTORY}/remote/$SUBMODULE_NAME"
 FILENAMES=("sample0" "sample1 sample3") 
 FILENAMES_TAG=("sample0 sample1 sample4")
 FILENAMES_BRANCH=("sample0 sample1 sample2") 
@@ -40,6 +42,7 @@ FILE_ON_BRANCH_ONLY="sample2"
 FILE_ON_TAG_ONLY="sample4"
 FILE_ON_MAIN_ONLY="sample3"
 FILE_TO_BE_DELETED="sample0" 
+FILE_TO_BE_DELETED_SUBMODULE="sub_sample0"
 FILE_TO_BE_CREATED="new_file"
 FILE_TO_BE_MODIFIED=$FILE_TO_BE_CREATED
 UNTRACKED_FILE="untracked_file"
@@ -47,12 +50,13 @@ TAG_NAME="tagging_point"
 TAG_FLAG="tag_flag"
 BRANCH_NAME="secondary"
 
-bash creation_repo.sh -s &> /dev/null
+bash creation_repo.sh -s #&> /dev/null
 
 #output function
 section(){
     echo "------------------------------ $1 ------------------------------"
 }
+
 #check functions
 cloning_check(){
     local input=("$@")
@@ -156,6 +160,26 @@ modification_check(){
     cd ..
 }
 
+modification_submodule_check(){
+    local repo_name=$1
+    cd $repo_name/$SUBMODULE_NAME
+    if [ -f $FILE_TO_BE_CREATED ]; then
+        echo "The new file has been imported."
+        modification_submodule_result=0
+        
+    else
+        echo "The new file has not been imported."
+        modification_submodule_result="1"
+    fi
+    if [ -f "$FILE_TO_BE_DELETED_SUBMODULE" ]; then
+        echo "$FILE_TO_BE_DELETED_SUBMODULE has not been deleted."
+        modification_submodule_result="1"
+    else    
+        echo "$FILE_TO_BE_DELETED_SUBMODULE has been deleted."
+    fi
+    cd ..
+}
+
 switching_branch_check(){
     local repo_name=$1
     cd $repo_name
@@ -210,23 +234,39 @@ conflict_check(){
 
 #intermediate functions
 modification_remote(){
-    echo "remote : $LOCAL_REMOTE"
-    echo "pwd : $(pwd)"
     cd $LOCAL_REMOTE
     touch $FILE_TO_BE_CREATED
     echo "new text" > $FILE_TO_BE_CREATED
     rm $FILE_TO_BE_DELETED
     git add $FILE_TO_BE_CREATED $FILE_TO_BE_DELETED &> /dev/null
-    git commit -m "$FILE_TO_BE_CREATED created and $FILE_TO_BE_DELETED deleted" #&> /dev/null
+    git commit -m "$FILE_TO_BE_CREATED created and $FILE_TO_BE_DELETED deleted" &> /dev/null
     cd ../..
 }
 
+
 undo_modification_remote(){
     cd $LOCAL_REMOTE
     git revert --no-edit HEAD &> /dev/null
     cd ../..
 }
 
+modification_submodule(){
+    cd $LOCAL_REMOTE_SUBMODULE
+    pwd
+    touch $FILE_TO_BE_CREATED
+    echo "new text" > $FILE_TO_BE_CREATED
+    rm $FILE_TO_BE_DELETED_SUBMODULE
+    git add $FILE_TO_BE_CREATED $FILE_TO_BE_DELETED_SUBMODULE &> /dev/null
+    git commit -m "$FILE_TO_BE_CREATED created and $FILE_TO_BE_DELETED_SUBMODULE deleted" #&> /dev/null
+    cd ../..
+}
+
+undo_modification_submodule(){
+    cd $LOCAL_REMOTE_SUBMODULE
+    git revert --no-edit HEAD &> /dev/null
+    cd ../..
+}
+
 add_untracked_file(){
     local repo_name=$1
     cd $repo_name
@@ -265,7 +305,8 @@ undo_changing_tag(){
     git checkout $TAG_FLAG &> /dev/null
     git tag -f $TAG_NAME &> /dev/null #move locally
     git tag --delete $TAG_FLAG &> /dev/null #delete locally
-    cd ..
+    git checkout main &> /dev/null
+    cd ../..
 }
 
 
@@ -276,7 +317,7 @@ test0 (){
     if [ -d $REPO_NAME ]; then
         rm -rf $REPO_NAME
     fi
-    ./git_update.sh -d $REPO_NAME $REMOTE #&> /dev/null
+    ./git_update.sh -d $REPO_NAME $REMOTE &> /dev/null
     #checks
     cloning_check $REPO_NAME ${FILENAMES[@]}
     history_check $REPO_NAME
@@ -318,7 +359,7 @@ test2(){
     fi
     ./git_update.sh -d $REPO_NAME -r $BRANCH_NAME $REMOTE &> /dev/null
     #checks
-    cloning_check $REPO_NAME ${FILENAMES_BRANCH[@]} #we do not check for all files, especially not those specific to the branch.
+    cloning_check $REPO_NAME ${FILENAMES_BRANCH[@]}
     history_check $REPO_NAME
     branch_check $REPO_NAME
 
@@ -339,7 +380,7 @@ test3(){
     fi
     #clone the repo in its last state
     git clone --recurse-submodules --shallow-submodules --depth 1 $REMOTE &> /dev/null
-    #modify the remote from elsewhere
+    #modify the remote
     modification_remote
     #make git_update.sh update the repository
     cd $REPO_NAME
@@ -368,7 +409,7 @@ test4(){
     fi
     #clone the repo in its last state
     git clone --recurse-submodules --shallow-submodules --depth 1 $REMOTE &> /dev/null
-    #modify the remote from elsewhere
+    #modify the remote
     modification_remote
     #add an untracked file
     add_untracked_file $REPO_NAME
@@ -384,11 +425,11 @@ test4(){
     undo_modification_remote 
     remove_untracked_file $REPO_NAME
 
-    case3=$((modification_result+history_result+untracked_result))
-    if [ "$case3" = "0" ]; then
-        echo "case 3, fast-forward update on main: OK"
+    case4=$((modification_result+history_result+untracked_result))
+    if [ "$case4" = "0" ]; then
+        echo "case 4, fast-forward update on main with untracked file: OK"
     else
-        echo "case 3, fast-forward update on main: FAIL"
+        echo "case 4, fast-forward update on main with untracked file: FAIL"
     fi
 }
 
@@ -403,7 +444,7 @@ test5(){
     git clone --recurse-submodules --shallow-submodules --depth 1 $REMOTE &> /dev/null
     #modify the local repo
     modification_local $REPO_NAME
-    #modify the remote from elsewhere
+    #modify the remote
     modification_remote
     #make git_update.sh update the local repository
     cd $REPO_NAME
@@ -481,21 +522,18 @@ test8(){
     git clone --recurse-submodules --shallow-submodules --depth 1 $REMOTE &> /dev/null
     #call git_update.sh with a tag
     cd $REPO_NAME
-    ../git_update.sh -r $TAG_NAME $REMOTE #&> /dev/null
+    ../git_update.sh -r $TAG_NAME $REMOTE &> /dev/null
     cd ..
     #intermediate check to make sure that we are starting on the initial position of the tag
-    echo "first position of the tag"
-    pwd
     switching_tag_check $REPO_NAME
-    #change the position of the tag from elsewhere
+    #change the position of the tag
     changing_tag
     #call git_update.sh again to go to the new position of the tag
     cd $REPO_NAME
-    pwd
-    ../git_update.sh -r $TAG_NAME $REMOTE #&> /dev/null
+    ../git_update.sh -r $TAG_NAME $REMOTE &> /dev/null
     cd ..
     #put back the remote in its initial state
-    #undo_changing_tag
+    undo_changing_tag
 
     #checks
     echo "second position of the tag"
@@ -507,9 +545,38 @@ test8(){
     else
         echo "case 8, tag-changing update: FAIL"
     fi
-
 }
 
+test9(){
+#CASE 9: git updated fast-forward on submodule on main
+    section TEST9
+    #if it exists, delete the directory
+    if [ -d $REPO_NAME ]; then
+        rm -rf $REPO_NAME
+    fi
+    #clone the repo in its last state
+    git clone --recurse-submodules --shallow-submodules --depth 1 $REMOTE &> /dev/null
+    #modify the remote
+    modification_submodule
+    #make git_update.sh update the repository
+    cd $REPO_NAME
+    echo "moment fatidique"
+    ../git_update.sh $REMOTE #&> /dev/null
+    cd ..
+    #checks
+    modification_submodule_check $REPO_NAME
+    history_check $REPO_NAME
+    #cleaning
+    undo_modification_submodule
+
+    case9=$((modification_submodule_result+history_result))
+    if [ "$case9" = "0" ]; then
+        echo "case 9, fast-forward update on submodule on main: OK"
+    else
+        echo "case 9, fast-forward update on submodule on main: FAIL"
+    fi
+} 
+
 while getopts ":hn:a" option; do
    case $option in
       h) # display Help
@@ -535,6 +602,7 @@ if [ "$ALL_TESTS" = "true" ]; then
     test6 
     test7 
     test8 
+    test9
 elif [ -n "$TEST_NUM" ]; then
     #in order to only create the temporary clone once if we execute all tests
     case $TEST_NUM in
@@ -556,6 +624,8 @@ elif [ -n "$TEST_NUM" ]; then
             test7;;
         8) 
             test8;;
+        9)
+            test9;;
         *)
             echo "Error: Invalid test number"
             exit;;