Fix error if user cds into a .git directory

In this case is was previously not possible to get the untracked
status. Now we temporarily change the directory to the repo root
folder and then get the list of untracked files.

functions/vcs.zsh

@@ -8,17 +8,35 @@
 
 set_default POWERLEVEL9K_VCS_SHOW_SUBMODULE_DIRTY false
 function +vi-git-untracked() {
-    [[ -z "${vcs_comm[gitdir]}" || "${vcs_comm[gitdir]}" == "." ]] && return
-
-    if [[ "$POWERLEVEL9K_VCS_SHOW_SUBMODULE_DIRTY" == "true" && "$(command git submodule foreach --quiet --recursive 'command git ls-files --others --exclude-standard')" != "" ]]; then
+    [[ -z "${vcs_comm[gitdir]}" ]] && return
+
+    # If we are in a repos root folder, vcs_comm[gitdir] yields ".git".
+    # Inside the .git dir itself (and not a subdir of it) the variable
+    # yields ".". In any other case (either a subdirectory of .git or
+    # the repo itself), the value of vcs_comm[gitdir] is the absolute
+    # path to the .git directory.
+    # Therefore we can step up a directory, if we are inside the .git
+    # folder. And in any other case, use the parent directory of the
+    # gitdir.
+    local repoDir="."
+    # Getting the parent dir of the current dir "." is still ".", so
+    # is is safe to do this always.
+    [[ "${vcs_comm[gitdir]}" != ".git" ]] && repoDir="${vcs_comm[gitdir]:h}"
+    [[ "${vcs_comm[gitdir]}" == "." ]] && repoDir=".."
+
+    if [[ "$POWERLEVEL9K_VCS_SHOW_SUBMODULE_DIRTY" == "true" && "$(cd ${repoDir} && command git submodule foreach --quiet --recursive 'command git ls-files --others --exclude-standard')" != "" ]]; then
         hook_com[unstaged]+=" $(print_icon 'VCS_UNTRACKED_ICON')"
         VCS_WORKDIR_HALF_DIRTY=true
-    elif [[ "$(command git ls-files --others --exclude-standard)" != "" ]]; then
+    elif [[ "$(cd ${repoDir} && command git ls-files --others --exclude-standard)" != "" ]]; then
         hook_com[unstaged]+=" $(print_icon 'VCS_UNTRACKED_ICON')"
         VCS_WORKDIR_HALF_DIRTY=true
     else
         VCS_WORKDIR_HALF_DIRTY=false
     fi
+
+    # If we are in any other directory than the repo root, we want
+    # to go back a directory.
+    [[ "${vcs_comm[gitdir]}" != ".git" ]] && cd - >/dev/null
 }
 
 function +vi-git-aheadbehind() {