I tried running Maven install using Java 10 on the latest version of the repository 3.0.0-beta6-SNAPSHOT but got a NullPointerException.  I found that version 2.20.1 is reported to have an issue  with 
org.apache.maven.surefire.shade.org.apache.commons.lang3.SystemUtils.isJavaVersionAtLeast(SystemUtils.java:1626)
I think git-client-plugin just needs to be upgraded to the fixed version of Surefire: 2.21.0

maven install -e

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.20.1:test (default-test) on project git-client: Execution default-test of goal org.apache.maven.plugins:maven-surefire-plugin:2.20.1:test failed.: NullPointerException -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.20.1:test (default-test) on project git-client: Execution default-test of goal org.apache.maven.plugins:maven-surefire-plugin:2.20.1:test failed.
{{ at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:213)}}
{{ at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:154)}}
{{ at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:146)}}
{{ at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)}}
{{ at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)}}
{{ at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)}}
{{ at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)}}
{{ at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)}}
{{ at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)}}
{{ at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)}}
{{ at org.apache.maven.cli.MavenCli.execute (MavenCli.java:954)}}
{{ at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)}}
{{ at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)}}
{{ at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)}}
{{ at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)}}
{{ at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)}}
{{ at java.lang.reflect.Method.invoke (Method.java:564)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)}}
{{ at org.codehaus.classworlds.Launcher.main (Launcher.java:47)}}
Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default-test of goal org.apache.maven.plugins:maven-surefire-plugin:2.20.1:test failed.
{{ at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:148)}}
{{ at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:208)}}
{{ at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:154)}}
{{ at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:146)}}
{{ at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)}}
{{ at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)}}
{{ at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)}}
{{ at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)}}
{{ at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)}}
{{ at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)}}
{{ at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)}}
{{ at org.apache.maven.cli.MavenCli.execute (MavenCli.java:954)}}
{{ at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)}}
{{ at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)}}
{{ at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)}}
{{ at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)}}
{{ at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)}}
{{ at java.lang.reflect.Method.invoke (Method.java:564)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)}}
{{ at org.codehaus.classworlds.Launcher.main (Launcher.java:47)}}
Caused by: java.lang.NullPointerException
{{ at org.apache.maven.surefire.shade.org.apache.commons.lang3.SystemUtils.isJavaVersionAtLeast (SystemUtils.java:1626)}}
{{ at org.apache.maven.plugin.surefire.AbstractSurefireMojo.getEffectiveJvm (AbstractSurefireMojo.java:2107)}}
{{ at org.apache.maven.plugin.surefire.AbstractSurefireMojo.getForkConfiguration (AbstractSurefireMojo.java:1976)}}
{{ at org.apache.maven.plugin.surefire.AbstractSurefireMojo.executeProvider (AbstractSurefireMojo.java:1111)}}
{{ at org.apache.maven.plugin.surefire.AbstractSurefireMojo.executeAfterPreconditionsChecked (AbstractSurefireMojo.java:954)}}
{{ at org.apache.maven.plugin.surefire.AbstractSurefireMojo.execute (AbstractSurefireMojo.java:832)}}
{{ at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)}}
{{ at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:208)}}
{{ at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:154)}}
{{ at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:146)}}
{{ at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)}}
{{ at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)}}
{{ at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)}}
{{ at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)}}
{{ at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)}}
{{ at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)}}
{{ at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)}}
{{ at org.apache.maven.cli.MavenCli.execute (MavenCli.java:954)}}
{{ at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)}}
{{ at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)}}
{{ at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)}}
{{ at jdk.internal.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)}}
{{ at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)}}
{{ at java.lang.reflect.Method.invoke (Method.java:564)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:289)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:229)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:415)}}
{{ at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:356)}}
{{ at org.codehaus.classworlds.Launcher.main (Launcher.java:47)}}