use comparison instead of assignment

Examples.md

@@ -349,9 +349,9 @@ fstash() {
     sha="${out[-1]}"
     sha="${sha%% *}"
     [[ -z "$sha" ]] && continue
-    if [[ "$k" = 'ctrl-d' ]]; then
+    if [[ "$k" == 'ctrl-d' ]]; then
       git diff $sha
-    elif [[ "$k" = 'ctrl-b' ]]; then
+    elif [[ "$k" == 'ctrl-b' ]]; then
       git stash branch "stash-$sha" $sha
       break;
     else