Redesign gitignore plugin

- removed code that fetches completions frim gitignore.io each time fish
  is started -- makes logins slow!
- gi.load becomes gi.fish, only contains gi function
- add _update_gi_completions.fish: fetches list of completions from
  gitignore.io and places it into ~/.config/fish/completions
- modify gi function to accept update-completions argument

plugins/gi/_update_gi_completions.fish

+function _update_gi_completions -d "Update completions for gitignore.io"
+  set compl_dir ~/.config/fish/completions
+  set compl_file "$compl_dir/gi.fish"
+
+  # Download list of ignore types
+  set -l gi_list (gi list | tr ',' ' ')
+  if test -z $gi_list
+    echo "No result returned from gitignore.io" >&2
+    return 1
+  end
+
+  # Backup existing completions
+  if test -e $compl_file
+    mv -f $compl_file {$compl_file}.bak
+  else if not test -d $compl_dir
+    mkdir -p $compl_dir
+  end
+
+  # Output new completions
+  echo complete -c gi -a \"update-completions $gi_list\" >$compl_file
+end

plugins/gi/gi.fish

+function gi -d "gitignore.io cli for fish"
+  if test $argv[1] = 'update-completions'
+    _update_gi_completions
+    return $status
+  end
+
+  set -l params (echo $argv|tr ' ' ',')
+  curl -s http://www.gitignore.io/api/$params
+end

plugins/gi/gi.load

-# gitignore.io cli for fish
-
-function gi
-  set -l params (echo $argv|tr ' ' ',')
-  curl -s http://www.gitignore.io/api/$params
-end
-
-# enable the complation by invoking `gi list`
-if not set -q -g gi_list
-  ping -t 2 -c 1 -q gitignore.io >/dev/null
-  set gi_available $status
-
-  if test $gi_available
-    set -g gi_list (gi list| tr ',' ' ' ^/dev/null)
-  end
-end
-
-complete -c gi -a "$gi_list"