git: add alias that allows cd to the git-root

modules/git/README.md

@@ -208,6 +208,10 @@ Aliases
   - `gwX` removes files from the working tree and from the index recursively and
     forcefully.
 
+### Miscellaneous
+
+  - `g..` change to the top-level directory of the current repository.
+
 ### Shadows
 
 The following aliases may shadow system commands:

modules/git/alias.zsh

@@ -179,3 +179,6 @@ alias gwc='git clean -n'
 alias gwC='git clean -f'
 alias gwx='git rm -r'
 alias gwX='git rm -rf'
+
+# Miscellaneous
+alias g..='cd $(git-root || echo ".")'