As we all know, if a plugin (by a given name) already exists in the wp-content/plugins directory, then WordPress won't overwrite it. Instead it shows the "Destination folder already exists." error (and plugin install failed).
I'm just asking, if anyone can point me out what to deal (or telling me if it's not possible) to let my WordPress site automatically upgrade/overwrite an existing plugin through the upload-plugin page.
Update (Sept, 10th):
Is there any specific function/action that I should implement in my private plugin so when I try to upload (let say) a newer version of that plugin, my WordPress site would handle the deactivation-deletion steps and later install the newly uploaded plugin package?