[MBUILDCACHE-103] Allow incremental restore in case of plugin parameter mismatch

**[Réda Housni Alaoui](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=ralaoui)** opened **[MBUILDCACHE-103](https://issues.apache.org/jira/browse/MBUILDCACHE-103?redirect=false)** and commented

Property `groups` of `maven-surefire-plugin` allows to run a subset of tests matching the property value. E.g. `groups=foo` will only execute tests tagged with 'foo'.

If I run a build with `groups=foo`, and if a cache entry exists for `groups=null` (i.e. no test filter), I want the cache entry to be reused as much as possible and the `maven-surefire-plugin` to be run on top of that.

I think I need to specify that every non null value for groups should be considered as a skip value.
Following this, what I need is the ability to declare a reconcile entry in xml config file looking like this:

```xml

```

Could we introduce this `skipValueRegex` that would allow to match multiple skip values and fix my issue?

---

**Remote Links:**
- [GitHub Pull Request #177
](https://github.com/apache/maven-build-cache-extension/pull/177)

Start by reviewing the issue's proposed XML configuration and GitHub pull request #177, then trace how reconcile entries and maven-surefire-plugin parameters are processed. Done means a non-null groups value can reuse the groups=null cache entry while still running the requested Surefire tests, with coverage for the skipValueRegex behavior.

Written by the indexing model from the issue text.