[bobthefish] allow git untracked files override

Showing untracked files can be (very) slow on large NFS mounts. Allow the user to disable the '...' output when there are untracked files, either globally via fish config:

    set -g theme_display_git_untracked no

 or locally via git repo config:

    git config bash.showUntrackedFiles false

Fixes #434

fish_prompt.fish

@@ -13,6 +13,7 @@
 # You can override some default options in your config.fish:
 #
 #     set -g theme_display_git no
+#     set -g theme_display_git_untracked no
 #     set -g theme_display_hg yes
 #     set -g theme_display_virtualenv no
 #     set -g theme_display_ruby no
@@ -286,8 +287,12 @@ function __bobthefish_prompt_git -d 'Display the actual git state'
   set -l stashed (command git rev-parse --verify --quiet refs/stash >/dev/null; and echo -n '$')
   set -l ahead   (command git rev-list --left-right '@{upstream}...HEAD' ^/dev/null | awk '/>/ {a += 1} /</ {b += 1} {if (a > 0) nextfile} END {if (a > 0 && b > 0) print "±"; else if (a > 0) print "+"; else if (b > 0) print "-"}')
 
-  set -l new (command git ls-files --other --exclude-standard);
-  [ "$new" ]; and set new '…'
+  set -l new ''
+  set -l show_untracked (git config --bool bash.showUntrackedFiles)
+  if [ "$theme_display_git_untracked" != 'no' -a "$show_untracked" != 'false' ]
+    set new (command git ls-files --other --exclude-standard)
+    [ "$new" ]; and set new '…'
+  end
 
   set -l flags   "$dirty$staged$stashed$ahead$new"
   [ "$flags" ]; and set flags " $flags"