import hudson.FilePath
import hudson.remoting.VirtualChannel
import jenkins.MasterToSlaveFileCallable

import java.nio.charset.StandardCharsets

FilePath workspaceFilePath = build.getWorkspace()
def patchTempFile = workspaceFilePath.createTempFile('foo', '.patch')
try {
    println('Writing patch to temp file')
    def conn = (HttpURLConnection) new URL(build.environment.patchDownloadUrl).openConnection()

    int responseCode = conn.getResponseCode()
    if (responseCode == HttpURLConnection.HTTP_OK) {
        def contentDisposition = conn.getHeaderField("Content-Disposition")
        int index = contentDisposition.indexOf('filename=')
        if (index > 0) {
            filename = contentDisposition.substring(index + 10)
        }
        copyStream(conn.getInputStream(), patchTempFile.write())
    } else {
        if (conn.getErrorStream() == null) {
            println "Failed to download patch file, response code: ${responseCode}"
        } else {
            def errorBaos = new ByteArrayOutputStream()
            copyStream(conn.getErrorStream(), errorBaos)
            def errorMessage = new String(errorBaos.toByteArray(), StandardCharsets.UTF_8)
            println "Failed to download patch file, response code: ${responseCode}, response body: ${errorMessage}"
        }
        return -1
    }

    if (applyPatch(build.getWorkspace(), patchTempFile) != 0) {
        println 'Applying git patch failed!'
        return -1
    }

    println('Applying patch using git')

} finally {
    patchTempFile.delete()
}

static def applyPatch(FilePath workspaceFilePath, FilePath patchTempFilePath) {
    String command = "git apply ${patchTempFilePath.getName()}"
    patchTempFilePath.act(new MasterToSlaveFileCallable<Integer>() {
        @Override
        Integer invoke(File patchTempFile, VirtualChannel patchTempFileChannel) throws IOException, InterruptedException {
            println "executing ${command}"
            return workspaceFilePath.act(new MasterToSlaveFileCallable<Integer>() {
                @Override
                Integer invoke(File workspaceDir, VirtualChannel workspaceDirChannel) throws IOException, InterruptedException {
                    def proc = command.execute(null, workspaceDir)
                    def output = new StringWriter()
                    def error = new StringWriter()
                    proc.waitForProcessOutput(output, error)
                    println("exit value: ${proc.exitValue()}")
                    println("output: ${output}")
                    println("err: ${error}")
                    return proc.exitValue()
                }
            })
        }
    })
}

static def copyStream(InputStream inputStream, OutputStream outputStream) throws IOException {
    try {
        def byteCount = 0
        byte[] buffer = new byte[4096]
        int bytesRead
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, bytesRead)
            byteCount += bytesRead
        }
        outputStream.flush()
        return byteCount
    } finally {
        outputStream.close()
        inputStream.close()
    }

} 

FATAL: Remote call on agent failed
Also: hudson.remoting.Channel$CallSiteStackTrace: Remote call to channel
at hudson.remoting.Channel.attachCallSiteStackTrace(Channel.java:1784)
at hudson.remoting.Request.call(Request.java:199)
at hudson.remoting.RemoteInvocationHandler.invoke(RemoteInvocationHandler.java:288)
at com.sun.proxy.$Proxy6.fetch3(Unknown Source)
at hudson.remoting.RemoteClassLoader.prefetchClassReference(RemoteClassLoader.java:353)
at hudson.remoting.RemoteClassLoader.loadWithMultiClassLoader(RemoteClassLoader.java:258)
at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:228)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:589)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522)
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Class.java:398)
at hudson.remoting.MultiClassLoaderSerializer$Input.resolveClass(MultiClassLoaderSerializer.java:132)
at java.base/java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1995)
at java.base/java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1862)
at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2169)
at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1679)
at java.base/java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2464)
at java.base/java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:2358)
at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2196)
at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1679)
at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:493)
at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:451)
at hudson.remoting.UserRequest.deserialize(UserRequest.java:289)
at hudson.remoting.UserRequest.perform(UserRequest.java:189)
at hudson.remoting.UserRequest.perform(UserRequest.java:54)
at hudson.remoting.Request$2.run(Request.java:376)
at hudson.remoting.InterceptingExecutorService.lambda$wrap$0(InterceptingExecutorService.java:78)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)
java.lang.IllegalArgumentException: Unable to locate class file for class Script1$1
at hudson.remoting.Which.classFileUrl(Which.java:68)
at hudson.remoting.RemoteClassLoader$ClassLoaderProxy.fetch4(RemoteClassLoader.java:1014)
at hudson.remoting.RemoteClassLoader$ClassLoaderProxy.fetch3(RemoteClassLoader.java:1045)
at jdk.internal.reflect.GeneratedMethodAccessor6.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at hudson.remoting.RemoteInvocationHandler$RPCRequest.perform(RemoteInvocationHandler.java:924)
at hudson.remoting.Request$2.run(Request.java:376)
at hudson.remoting.InterceptingExecutorService.lambda$wrap$0(InterceptingExecutorService.java:78)
at org.jenkinsci.remoting.CallableDecorator.call(CallableDecorator.java:18)
at hudson.remoting.CallableDecoratorList.lambda$applyDecorator$0(CallableDecoratorList.java:19)
at jenkins.util.ContextResettingExecutorService$2.call(ContextResettingExecutorService.java:48)
at jenkins.security.ImpersonatingExecutorService$2.call(ImpersonatingExecutorService.java:82)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:833)
Also: hudson.remoting.Channel$CallSiteStackTrace: Remote call to agent
at hudson.remoting.Channel.attachCallSiteStackTrace(Channel.java:1784)
at hudson.remoting.UserRequest$ExceptionResponse.retrieve(UserRequest.java:356)
at hudson.remoting.Channel.call(Channel.java:1000)
at hudson.FilePath.act(FilePath.java:1186)
at hudson.FilePath.act(FilePath.java:1175)
at hudson.FilePath$act$1.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:128)
at Script1.applyPatch(Script1.groovy:46)
at Script1$applyPatch$0.callStatic(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallStatic(CallSiteArray.java:55)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callStatic(AbstractCallSite.java:197)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callStatic(AbstractCallSite.java:217)
at Script1.run(Script1.groovy:33)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:574)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:612)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:583)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript.evaluate(SecureGroovyScript.java:440)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript.evaluate(SecureGroovyScript.java:377)
at hudson.plugins.groovy.SystemGroovy.run(SystemGroovy.java:95)
at hudson.plugins.groovy.SystemGroovy.perform(SystemGroovy.java:59)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:816)
at hudson.model.Build$BuildExecution.build(Build.java:199)
at hudson.model.Build$BuildExecution.doRun(Build.java:164)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:524)
at hudson.model.Run.execute(Run.java:1899)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:44)
at hudson.model.ResourceController.execute(ResourceController.java:107)
at hudson.model.Executor.run(Executor.java:449)
Caused: java.lang.Error: Failed to deserialize the Callable object.
at hudson.remoting.UserRequest.perform(UserRequest.java:195)
at hudson.remoting.UserRequest.perform(UserRequest.java:54)
at hudson.remoting.Request$2.run(Request.java:376)
at hudson.remoting.InterceptingExecutorService.lambda$wrap$0(InterceptingExecutorService.java:78)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)
Caused: java.io.IOException: Remote call on agent failed
at hudson.remoting.Channel.call(Channel.java:1004)
at hudson.FilePath.act(FilePath.java:1186)
at hudson.FilePath.act(FilePath.java:1175)
at hudson.FilePath$act$1.call(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:47)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:128)
at Script1.applyPatch(Script1.groovy:46)
at Script1$applyPatch$0.callStatic(Unknown Source)
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallStatic(CallSiteArray.java:55)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callStatic(AbstractCallSite.java:197)
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callStatic(AbstractCallSite.java:217)
at Script1.run(Script1.groovy:33)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:574)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:612)
at groovy.lang.GroovyShell.evaluate(GroovyShell.java:583)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript.evaluate(SecureGroovyScript.java:440)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript.evaluate(SecureGroovyScript.java:377)
at hudson.plugins.groovy.SystemGroovy.run(SystemGroovy.java:95)
at hudson.plugins.groovy.SystemGroovy.perform(SystemGroovy.java:59)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:816)
at hudson.model.Build$BuildExecution.build(Build.java:199)
at hudson.model.Build$BuildExecution.doRun(Build.java:164)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:524)
at hudson.model.Run.execute(Run.java:1899)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:44)
at hudson.model.ResourceController.execute(ResourceController.java:107)
at hudson.model.Executor.run(Executor.java:449)