Some of the Go tests actually cloned remote repos, which meant slow tests, and tests failures if I was working offline. These changes allow all Go tests to run offline. The test code now clones local Git repos instead of remotes ones.
* Add otiai10/copy as a dependency
* Create repotest package for test code that needs to work with Git repos
* Add back missing test script for execute package
* Update git, pluginindex, and plugins package tests so they work offline
* Implement info command
* Remove duplicate and unneeded BATS tests from `main_test.go`
* remove download dir for plugin when removing plugin
* update plugins.Add function so downloads directory is created
* Create `plugins.New` function, updating existing code to use it
* Add another test for `hook.Run` function
* Enable `plugin_add_command.bats` tests for Go implementation of asdf
* Add `RunCallback` method to `Plugin` struct
* Update `plugins.Add` function to run `post-plugin-add` plugin callback script
* Handle Bash expression and scripts properly in `execute` package so `$@` is always set
* Create `pluginindex.Build` function
* Use `pluginindex` when no plugin URL provided for plugin add command
* Get more `plugin_add_command` BATS tests passing against Golang version
* Only use `pluginindex` when it is not disabled
* Update error message so it matches legacy format
* Add staticcheck.conf
