feat(manager/gradle): add support for apply from statements

[Churro]

Changes

• Adds support for apply from: 'somefile.gradle' statements
  • Enables dynamic inclusion of further, arbitrary files during the parsing operation of a gradle file. vars, deps and urls of included files are then evaluated in the context of the file that is currently parsed.
  • Implements parts of the corresponding Groovy DSL and Kotlin DSL.

No existing tests were changed/rewritten, therefore I don't expect any breaking changes.

Test repository: https://github.com/Churro/renovate-applyfrom/pulls

Implementation Notes

• extract.ts:

  • Files included via apply from do not necessarily have to be *.gradle, so they may not exist in packageFiles and are dynamically added, if missing.
  • If files are of type *.gradle, it may happen that they are parsed twice. It's ensured that extracted deps are still considered only once.

• parser.ts:

  • It's anachronistic to introduce readLocalFileSync() but I really don't see a reasonable way how to do this async.
    • The currently parsed file needs the included file the moment when apply from happens, not afterwards.
    • Parsing one or multiple included files ahead would probably incur a lot more complexity since you would need to go over all packageFiles at least twice and then selectively merge parsed infos. This step would need to be done in any case, also if no apply from is used in any file.
  • Files could, in theory, include themselves, which would lead to an endless loop. A recursionDepth check ensures this cannot happen, as it prevents "nested apply from" statements. If there is good reason, this could be increased to 1, 2, etc. and would still do no harm, but in any case the check remains a threshold to prevent cyclic includes.

Known Limitations

• No remote code loading, e.g. https://github.com/Netflix/glisten/blob/master/gradle/netflix-oss.gradle
• No support for project variables like $rootDir, e.g. apply(from = "${rootDir.path}/gradle/publish/publishJvm.gradle")

Context

• apply from is very commonly used (1, 2, 3, ...) with gradle and should therefore be supported
• Related to Resolve dynamic deps versions in gradle #15359 but not (yet) solving it

Documentation (please check one with an [x])

• I have updated the documentation, or
• No documentation update is required

How I've tested my work (please tick one)

I have verified these changes via:

• Code inspection only, or
• Newly added/modified unit tests, or
• No unit tests but ran on a real repository, or
• Both unit tests + ran on a real repository

[viceice]

See comment, i've prepared a commit to use async io (5min of work)

bdbc7c8

[zharinov]

I'm convinced by your reasoning and the implementation, looks good to me 👍

[viceice]

see @zharinov comments

[renovate-release]

🎉 This PR is included in version 32.104.0 🎉

The release is available on:

• GitHub release
• 32.104.0

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