Plugin Commit Check: Verify License Declarations

[Ipstenu]

I know we do some pre-flight checks on plugins before commit (like if the code 'complies' etc). Can we add in a check for readme.txt to verify that there's a line that starts License: and it's _not_ just that?

Like enforce people to actually darn well declare their license or no SVN. That would be a nice way to enforce the CYA :)

[dd32]

In [3897] I've started to ingest the license headers into the new plugin directory so we can run some stats to see what kind of impact this change would have.

Early indications are that probably about 50% of popular plugins list it, although they're haphazard in how they list the license (GPLv2 or later vs GPLv2+ vs GNU General Public License v2.0 or later vs GPL V2 or latest vs even GPLv2 or later (of-course) :) )

[Ipstenu]

Stage 1: Declare a license.

Stage 2: "As of Date X, your license must be on this list of GPLv2 (or later) compatible terms."?

We could probably get away with "License: GPLv[2|3]*" for much of it. Having to curate a list of acceptable terms would be a pain to start, but once it's done then it's just a mild annoyance.

[Ipstenu]

Use ​https://spdx.org/licenses/ to validate license format. If we could somehow automate checking "These are GPLv2+ compatible" that would be brilliant.

[Ipstenu]

Uploaded patch 1944.diff - This just checks that new plugins declared a license at all.

[dd32]

In 9648:

Plugin Directory: Require a license be specified in the readme.txt.

Props Ipstenu.
Fixes #4719.
See #1944.

[casiepa]

See also #5126

[dd32]

In 12526:

Plugin Directory: Ingest the License and License URI readme fields on plugin upload.

See #1944, [3897].