Better support for Gradle dependency version matching.

[thorntonrp]

Gradle's innate flexibility with how dependencies and versions can be managed, especially when using custom plugins, causes conflicts with the rigid expectations of Renovate's pattern matching. It would be extremely helpful if Renovate would allow us to provide a custom regular expression to assist renovate in finding and replacing versions.

For example, I use a Gradle plugin that allows me to define dependency versions in my gradle.properties file as shown below.

version/org.apache.commons/commons-text = 1.12.0, !1.2.*, !2.*
version/org.junit.jupiter/junit-jupiter = 5.10.0

I would like to be able to give renovate a custom regular expression on how to handle this scenario as shown in the following hypothetical renovate.json config:

{
    "packageRules": [
        {
            "matchManagers": "gradle",
            "matchDatasources": "maven",
            "description": "Match dependencies in gradle.properties with custom pattern",
            "matchFileNames": ["**/gradle.properties"],
            "customPattern": "^version/(?<groupId>[^/]+)/(?<artifactId>[^\\s=]*)\\s*=\\s*(?<version>[^\\s,]+)"
        }
    ]
}

As shown in the above example, the custom pattern would allow Renovate to extract the groupId, artifactId, and version in a manner that is flexible and generic. It can then determine if there are updates to the dependency and use the same regular expression pattern to replace the version.

This especially becomes important in multimodule Gradle projects which may be using third-party or custom gradle plugins defined within the project to avoid repetition and keep build scripts clean and easily maintainable. Such uses cases are currently not well supported by Renovate and force projects to use conventions that limit the usability of custom or third-party Gradle plugins.