travis: add PR license check for missing/not-valid license files

[0xc0170]

Summary of changes

The goal: check license offenders in pull requests

This is similar to what astyle does in Travis. We get list of files being changed. Because scancode does not support list of files being scanned but rather a file or directory, we copy files to SCANCODE folder. Execute scancode license check in this folder and check for offenders.

The rules there are: code files must have a license and SDPX identifier. If they don't, we print these files with their licenses and request review (Travis fails).

There is currently no ignore list as we have for astyle. I believe all code files in our codebase should have valid license (even if they are 3rd party).

Impact of changes

Migration actions required

Documentation

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Pull request type

[x] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results

[] No Tests required for this change (E.g docs only update)
[x] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers

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[ciarmcom]

@0xc0170, thank you for your changes.
@ARMmbed/mbed-os-tools @ARMmbed/mbed-os-hal @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

scancode is functional now ! We got 2 offenders in this branch and it found them. One is without license and one with non-permissive license 🎉 More testing ongoing

[0xc0170]

What it reports if there is no license or non permissive:

Found files with missing license details, please review and fix
File:  /hal/analogin_api.h : licenses found:  []
File:  /hal/buffer.h : licenses found:  [{'key': 'gpl-3.0', 'score': 95.74, 'name': 'GNU General Public License 3.0', 'short_name': 'GPL 3.0', 'category': 'Copyleft', 'is_exception': False, 'owner': 'Free Software Foundation (FSF)', 'homepage_url': 'http://www.gnu.org/licenses/gpl-3.0.html', 'text_url': 'http://www.gnu.org/licenses/gpl-3.0-standalone.html', 'reference_url': 'https://enterprise.dejacode.com/urn/urn:dje:license:gpl-3.0', 'spdx_license_key': 'GPL-3.0-only', 'spdx_url': 'https://spdx.org/licenses/GPL-3.0-only', 'start_line': 6, 'end_line': 10, 'matched_rule': {'identifier': 'gpl-3.0_96.RULE', 'license_expression': 'gpl-3.0', 'licenses': ['gpl-3.0'], 'is_license_text': False, 'is_license_notice': True, 'is_license_reference': False, 'is_license_tag': False, 'matcher': '3-seq', 'rule_length': 94, 'matched_length': 90, 'match_coverage': 95.74, 'rule_relevance': 100}}]

[0xc0170]

I cleaned up the branch (removed testing files), this is ready for review.

@SeppoTakalo this one replaces gnu license check we had, we can now find out more non permissive licences in the codebase.

[0xc0170]

I'll do one more test for changing file without SPDX identifier

[0xc0170]

I add a reason for offenders, see:

Found files with missing license details, please review and fix
File:  /hal/analogin_api.h : reason:  Missing SPDX identifier

[0xc0170]

OK, ready for review and I can squash the long history of nothing-but-fixes. It reports now the number of offenders:

"Needs review, 2 license issues found". We will be monitoring this and reporting meanwhile the codebase gets cleaned up.

Please review again (just the diff, not each commits, will be squashed into one)

[0xc0170]

• I will remove 2 offenders for testing (you can review what it reports in license check now)

[0xc0170]

@adbridge Please review, I've just fixed printing the offenders (was skipped). I can squash this once approved and 2 files for testing removed.

[adbridge]

Where has the license header gone here ?

[adbridge]

Why has SPDX line gone ?

[0xc0170]

testing purpose (to see what travis reportS) as stated earlier. I'l lrevert this with rebase

[0xc0170]

Rebased, the test files removed, history cleaned up.

Pull request has been modified.

[0xc0170]

CI started

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 6
Build artifacts