git: Alias and function cleanup and formatting for clarity

Changes:
- Prefer longer form of git switch for better clarity.
- Move `-S` (`--gpg-sign`) in all the alias definitions to  the end to
  allow custom keyid.
- Simplify operations in helper functions git native calls.
- Apply minor reformatting and rearranging.

modules/git/functions/git-stash-dropped

@@ -16,7 +16,7 @@ command git fsck --unreachable 2> /dev/null \
   | grep 'commit' \
   | awk '{print $3}' \
   | command git log \
-      --pretty=format:${_git_log_oneline_format} \
+      --pretty=format:$_git_log_oneline_format \
       --extended-regexp \
       --grep="${1:-(WIP )?[Oo]n [^:]+:}" \
       --merges \