Summary:
Split out the register backend function from being a private function. A
backend is a table that will define all of the attributes for a run function.
The attributes are as follows:
- **command** The name of the command that will be registered as a vim user command.
- **items** The callback function that will be passed to the run function that will gather the items for selection
- **callback** The callback function run when an item is selected
The following are optional:
- **keymap** The string passed to `nvim_set_keymap`, this will always be registered in normal mode
- **description** The text description that will be used in the user command
- **name** The name of the backend, this will fallback to the command if its not set
It will also allow to register a backend in a couple of different ways:
- With a backend module table
- With a backend module name
- With a backend module name and override options
This will look for for a lua module `ivy.backends.files`. The module will be
required and registered as a backend.
```lua
register_backend "ivy.backends.files"
```
This will do the same with the module string however, before the backend is
registered the keymap will be overridden
```lua
register_backend({ "ivy.backends.file", { keymap = "<C-p>" } })
```
Test Plan:
CI / Manual testing locally
Ade Attwood
91b6db9d76