Problem: No way to have full control over how plugin is loaded.
Although `:packadd!` has small side effects (only adds plugin
directory to 'runtimepath'; and maybe its 'after/' subdirectory), it
still has side effects. For example, 'plugin/' directories are still
loaded during startup (as part of `:h load-plugins`).
Solution: Allow function `opts.load` that has full control over how
plugin is loaded.
Problem: the `load=true` in `vim.pack.add()` means that `:packadd` is
executed even during startup. This leads to force source of 'plugin/',
which breaks the intended loading order (`:h load-plugins`) and
results into sourcing them twice. This also makes it ignore
`--noplugin` argument.
Using `:packadd!` during startup is more appropriate, while `:packadd`
afterwards is still more favorable to actually force 'plugin/' source
(as there is no pre-defined mechanism that will load them later).
Solution: have `load=false` default during startup, `true` - afterwards.
Problem:
Error when adding a plugin will make all following plugins not
`:packadd`ed
Solution:
- add() should handle errors from :packadd with pcall()
Co-authored-by: Evgeni Chasnovski <evgeni.chasnovski@gmail.com>
Co-authored-by: Justin M. Keyes <justinkz@gmail.com>
