Add a 'force' option

Abort patching a project if there's uncommited changes. Give the user an
option to 'force' overwritten their uncommited changes

Change-Id: Ie6952e8cdb432b94fcc96f64962544f7fb7e977e

vendorsetup.sh

@@ -148,6 +148,14 @@ __patch_tree()
             (
                set -e
                if branch ${PRJ} ; then
+                  if [[ -n $(git status --porcelain) ]]; then
+                     if [[ $1 != "force" ]]; then
+                        echo "ERROR: You have uncommited changes in ${PRJ}"
+                        echo "You may force overwriting these changes"
+                        echo "with |source build/envsetup.sh force|"
+                        exit 1
+                     fi
+                  fi
                   # Ensure the project is clean before applying patches to it
                   git reset --hard HEAD > /dev/null
                   git clean -dfx
@@ -222,6 +230,7 @@ if [[ -z $1 ]]; then
 else
    case $1 in
    clean) __abandon_tree ;;
+   force) __patch_tree force ;;
    np) echo "Skipping patch tree step...";;
    *) [[ -z "$PS1" ]] && __patch_tree || echo Error: Unknown command: $1
    esac