Merge pull request #64 from Mellbourn/fix-negative-comp-words

Including tweaks to conditional statements

I think the original conditionals would always be false. That prevents
using completions which rely on identifying the penultimate and
antepenultimate portions of typed commandline.

completion/yadm.bash_completion

@@ -9,8 +9,14 @@ if declare -F _git > /dev/null; then
   _yadm() {
 
     local current=${COMP_WORDS[COMP_CWORD]}
-    local penultimate=${COMP_WORDS[COMP_CWORD-1]}
-    local antepenultimate=${COMP_WORDS[COMP_CWORD-2]}
+    local penultimate
+    if [ "$((COMP_CWORD-1))" -ge "0" ]; then
+      penultimate=${COMP_WORDS[COMP_CWORD-1]}
+    fi
+    local antepenultimate
+    if [ "$((COMP_CWORD-2))" -ge "0" ]; then
+      antepenultimate=${COMP_WORDS[COMP_CWORD-2]}
+    fi
 
     local GIT_DIR
     # shellcheck disable=SC2034