From 17d93758be67d6dcf7ff019347780bd665bd960b Mon Sep 17 00:00:00 2001
From: RichardG867 <richardg867@gmail.com>
Date: Wed, 24 Nov 2021 20:24:06 -0300
Subject: [PATCH] Jenkins: Switch strategy for polled commit detection

---
 .ci/Jenkinsfile | 83 ++++++++++++++++++++++---------------------------
 1 file changed, 37 insertions(+), 46 deletions(-)

diff --git a/.ci/Jenkinsfile b/.ci/Jenkinsfile
index a53c461c7..53504ef50 100644
--- a/.ci/Jenkinsfile
+++ b/.ci/Jenkinsfile
@@ -81,24 +81,29 @@ def presetFlags = [
 def anyFailure = false
 
 def gitClone(repository, branch) {
-	/* Read git tag from environment or set the default one. */
-	if (env.GIT_COMMIT == null)
-		env.GIT_COMMIT = "*/$branch"
-	println "[-] Using git tag [${env.GIT_COMMIT}]"
-
 	/* Clean workspace. */
 	cleanWs()
 
 	/* Use stashes to avoid performing multiple clones. */
 	if (env.GIT_STASHED != 'true') {
 		/* Perform clone/checkout. */
-		def scmVars = checkout poll: false,
+		def scmVars = checkout poll: true,
 				       changelog: true,
 				       scm: [$class: 'GitSCM',
-					     branches: [[name: env.GIT_COMMIT]],
-					     extensions: [[$class: 'LocalBranch', localBranch: branch]],
+					     branches: [[name: branch]],
 					     userRemoteConfigs: [[url: repository]]]
-		env.GIT_COMMIT = scmVars.GIT_COMMIT
+
+		if (env.GIT_COMMIT == null) {
+			/* Save the current HEAD commit. */
+			env.GIT_COMMIT = scmVars.GIT_COMMIT
+		} else {
+			/* Checkout the commit read from the polling log. */
+			if (isUnix())
+				sh "git checkout ${env.GIT_COMMIT} || exit 0"
+			else
+				bat "git checkout ${env.GIT_COMMIT} || exit /b 0"
+		}
+		println "[-] Using git commit [${env.GIT_COMMIT}]"
 
 		/* Stash data and mark it as stashed. */
 		stash name: 'git'
@@ -147,46 +152,32 @@ pipeline {
 
 			steps {
 				script {
-					/* Hack to extract the current HEAD commit from this build's git polling
-					   log. This avoids a race condition where HEAD changes in the time period
-					   between Jenkins polling the git repository and the first build node
-					   performing the first git clone once ready. (See issue JENKINS-20518) */
-					if (env.GIT_COMMIT == null) {
-						/* This must run on the master node to read the polling log. */
-						node('master') {
-							/* Ignore exceptions as this is not really critical. */
-							try {
-								/* Switch to this build's directory. */
-								dir("${env.JENKINS_HOME}/jobs/${env.JOB_NAME}/builds/${env.BUILD_NUMBER}") {
-									/* Parse polling log. */
-									def pollingLog = readFile file: 'polling.log'
-									def match = pollingLog =~ /Latest remote head revision on [^ ]+ is: ([a-zA-Z0-9]+)/
-									if (match && match[0]) {
-										env.GIT_COMMIT = match[0][1]
-										println "[-] Read git tag [${env.GIT_COMMIT}] from polling log"
-									}
+					/* Extract the polled commit from the polling log, so that git checkout can be used
+					   to avoid JENKINS-20518 race conditions caused by two pushes too close together. */
+					node('master') { /* must run on master node to read polling log */
+						/* Ignore exceptions as this is not really critical. */
+						try {
+							/* Switch to this build's directory. */
+							dir("${env.JENKINS_HOME}/jobs/${env.JOB_NAME}/builds/${env.BUILD_NUMBER}") {
+								/* Parse polling log. */
+								def pollingLog = readFile file: 'polling.log'
+								def match = pollingLog =~ /Latest remote head revision on [^ ]+ is: ([a-zA-Z0-9]+)/
+								if (match && match[0]) {
+									env.GIT_COMMIT = match[0][1]
+									println "[-] Read git commit [${env.GIT_COMMIT}] from polling log"
 								}
-							} catch (e) {}
-						}
+							}
+						} catch (e) {}
+					}
 
-						/* Perform a git clone on any node to save polling data and,
-						   if polling log parsing failed, get the current HEAD commit. */
-						node {
-							/* Clean workspace. */
-							cleanWs()
+					/* Adding to the above, run a git clone as soon as possible on any node
+					   to further avoid race conditions caused by busy node executor delays. */
+					node {
+						/* Run git clone. */
+						gitClone(repository, branch)
 
-							/* Perform clone/checkout. */
-							def scmVars = checkout poll: true,
-									       changelog: false,
-									       scm: [$class: 'GitSCM',
-										     branches: [[name: branch]],
-										     userRemoteConfigs: [[url: repository]]]
-							if (env.GIT_COMMIT == null)
-								env.GIT_COMMIT = scmVars.GIT_COMMIT
-
-							/* Clean workspace again. */
-							cleanWs()
-						}
+						/* Clean workspace, in case this is running in a non-build node. */
+						cleanWs()
 					}
 
 					/* Create source tarball. */