Create `omf.update` function

Update and install were one thing before.

pkg/omf/cli/omf.update.fish

+function omf.update -a name
+  function __omf.update.success
+    echo (omf::em)"✔ $argv successfully updated."(omf::off)
+  end
+
+  function __omf.update.error
+    echo (omf::err)"Could not update $argv."(omf::off) 1^&2
+  end
+
+  if test \( -e $OMF_PATH/themes/$name \) -o \( -e $OMF_CONFIG/themes/$name \)
+    set install_type "theme"
+    set parent_path "themes"
+  else
+    set install_type "package"
+    set parent_path "pkg"
+  end
+
+  for path in {$OMF_PATH,$OMF_CONFIG}/pkg/$name
+    not test -e "$path/.git"; and continue
+
+    omf.repo.pull $path; and set return_success
+  end
+
+  set -q return_success; and __omf.update.success "$name"
+end

pkg/omf/omf.fish

@@ -139,10 +139,12 @@ function omf -d "Oh My Fish"
         echo (omf::err)"Oh My Fish failed to update."(omf::off)
         echo "Please open a new issue here → "(omf::em)"github.com/oh-my-fish/oh-my-fish/issues"(omf::off)
       end
-      omf.theme (cat $OMF_CONFIG/theme)
-      omf.install_package (omf.packages.list --installed --plugin)
-      refresh
 
+      for package in (omf.packages.list --installed)
+        omf.update $package
+      end
+
+      refresh
     case "*"
       echo (omf::err)"$argv[1] option not recognized"(omf::off) 1^&2
       return $OMF_UNKNOWN_OPT