As a new plugin developer, like many I learned a lot about WordPress plugin development by reviewing the Codex, diving in, and reading numerous 3rd party tutorials and blog posts online, written by generous WP veterans. From one place or another, I pieced together the big picture and got most everything answered for myself. However, a number of questions about plugin development and the directory submission process lingered in my mind (and some still do), undocumented as far as I could tell, and took a little while to figure out.
So I thought I'd "fill in the blanks" here about several of those loose ends that I figured out for myself, in case other newbie plugin developers are having the same question marks appear in their heads. If you're currently in the plugin learning or launching process, you may want to look over this tips list alongside all the other helpful information out there about WP plugins.
Uploading Your Plugin
The plugin uploading system for the WP Plugin Directory doesn't work via FTP. Instead, server-side software called Subversion ("SVN") houses both WordPress and all plugins in the WP Plugin Directory. You'd obtain a Subversion client, such as TortoiseSVN, and use it to access the repository. You then "Checkout" your files (even your empty repository area the first time), add your updates to your local folder, then "Checkin/Commit" your updates to the repository. Within ~15 minutes, your updates will be live.
First though, you'll need to gain access to the repository by being granted so by WP.
WP Plugin Directory Submission
After you've finished creating and testing your new plugin, you'll probably want to submit it to the central WP Plugin Directory (if appropriate). The process is this: You'll submit your request, which creates a placeholder repository download page (not publicly searchable). Within a few days someone at WP will (hopefully) approve your request, granting you permission to upload your plugin into the Subversion repository using your current WordPress.org username and password. The ball's now in your court, and your directory page is live, capturing (and updating every ~15 minutes) your plugin files, as uploaded into SVN.
Tip: Before applying for a SVN repository account, be sure to create a "homebase" for your plugin on your own website. Evident on such a page would be the reason the plugin exists, what it does, a general overview, and perhaps detailed documentation. Make the plugin downloadable already from your own website. You want the plugin to be able to stand on its own 2 feet before it can be hosted in the WP Plugin Directory.
On the application form, the "Plugin URL" field, while optional, is where you'd put a link to your plugin's information/home page on your site. Also, give some thought to how you name your plugin on that form (more info on that down below).
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