Show update prompt when running bash-it update

This utilizes the body of the merged PR requests to show the commits
that are included in this update. It gives the user a chance to
decline the upgrades by pressing n or N.

lib/helpers.bash

@@ -181,6 +181,11 @@ _bash-it_update() {
   status="$(git rev-list master..${BASH_IT_REMOTE}/master 2> /dev/null)"
 
   if [[ -n "${status}" ]]; then
+    git log --merges --format="%h: %b (%an)" master..${BASH_IT_REMOTE}/master
+    echo ""
+    read -e -n 1 -p "Would you like to update to $(git log -1 --format=%h origin/master)? [Y/n] " RESP
+    case $RESP in
+      [yY]|"")
         git pull --rebase &> /dev/null
         if [[ $? -eq 0 ]]; then
           echo "Bash-it successfully updated."
@@ -193,6 +198,14 @@ _bash-it_update() {
         else
           echo "Error updating Bash-it, please, check if your Bash-it installation folder (${BASH_IT}) is clean."
         fi
+        ;;
+      [nN])
+        echo "Not upgrading…"
+        ;;
+      *)
+        echo -e "\033[91mPlease choose y or n.\033[m"
+        ;;
+      esac
   else
     echo "Bash-it is up to date, nothing to do!"
   fi