[RelEng] Fix determination of baseline drop and git diff in promotion

Fix the computation of the baseline tag by ignoring the just promoted
drop.
Compare against the git-tag of the input dropId since the tag of the
promoted build is not yet applied at the time when the git comparison is
performed.
Additionally unify the computation of the git-tag for the promoted drop.

Author: HannesWell

JenkinsJobs/Releng/promoteBuild.jenkinsfile

@@ -62,6 +62,7 @@ pipeline {
 					echo "SIGNOFF_ISSUE: ${SIGNOFF_ISSUE}"
 					def build = utilities.matchBuildIdentifier("${DROP_ID}", { iBuild ->
 						assignEnvVariable('BUILD_LABEL', "${DROP_ID}")
+						assignEnvVariable('DROP_GIT_TAG', "${DROP_ID}")
 					}, { sBuild ->
 						if (sBuild.type == 'R') {
 							error "Releases cannot be promoted further: ${DROP_ID}"
@@ -70,6 +71,7 @@ pipeline {
 						if ("${CHECKPOINT}") {
 							error "Stable build DROP_ID=${DROP_ID} may only be promoted to release CHECKPOINT, which therefore must be empty: ${CHECKPOINT}"
 						}
+						assignEnvVariable('DROP_GIT_TAG', utilities.stableBuildGitTag("${DROP_ID}"))
 					})
 					assignEnvVariable('REPO_ID', "I${build.date}-${build.time}")
 
@@ -95,6 +97,8 @@ pipeline {
 					assignEnvVariable('DL_DROP_ID', "${DL_TYPE}-${DL_LABEL}-${build.date}${build.time}")
 					assignEnvVariable('MAINTENANCE_BRANCH', "R${BUILD_MAJOR}_${BUILD_MINOR}_maintenance")
 
+					assignEnvVariable('GIT_TAG', utilities.stableBuildGitTag("${DL_DROP_ID}"))
+					
 					if ("${SIGNOFF_ISSUE}".isEmpty()) {
 						echo '[WARNING] SIGNOFF_ISSUE was not defined. That is valid if no Unit Tests failures but otherwise should be defined.'
 					} else if ("${SIGNOFF_ISSUE}" ==~ '\\d+') {
@@ -149,11 +153,12 @@ pipeline {
 								if (baselineBuilds.isEmpty() && "${DL_TYPE}" == 'S') { // For M1 usually no previous stable build exists
 									baselineBuilds = utilities.listBuildDropDirectoriesOnRemote("${EP_ROOT}/eclipse/downloads/drops4", 'R*')
 								}
-								buildProperties.gitTag = utilities.stableBuildGitTag("${DL_DROP_ID}")
+								baselineBuilds.remove(env.DL_DROP_ID) // ignore the just promoted drop when determining the latest
+								buildProperties.gitTag = env.GIT_TAG
 								buildProperties.gitBaselineTag = utilities.stableBuildGitTag("${baselineBuilds.last()}")
 								echo "gitTag: ${buildProperties.gitTag}, gitBaselineTag: ${buildProperties.gitBaselineTag}"
 								dir("${WORKSPACE}/repository") {
-									def changedRepositories = utilities.listChangedGitRepositoryURLs(buildProperties.gitBaselineTag, buildProperties.gitTag)
+									def changedRepositories = utilities.listChangedGitRepositoryURLs(buildProperties.gitBaselineTag, "${DROP_GIT_TAG}") // git tag of promoted build not yet created
 									echo "Changed repositories: ${changedRepositories}"
 									buildProperties.gitReposChanged = changedRepositories
 								}
@@ -164,16 +169,13 @@ pipeline {
 			}
 		}
 		stage('Tag Build') {
-			environment {
-				TAG = "${utilities.stableBuildGitTag(DL_DROP_ID)}"
-			}
 			steps {
 				dir("${WORKSPACE}/repository") {
 					script {
 						utilities.runHereAndForEachGitSubmodule{
 							// Enforce the (re-)creation of the tag in case of a very late respin
-							sh 'git tag --force --annotate --message="${SIGNOFF_ISSUE}" ${TAG} HEAD'
-							utilities.gitPushTag("${TAG}", /*force*/ true)
+							sh 'git tag --force --annotate --message="${SIGNOFF_ISSUE}" ${GIT_TAG} HEAD'
+							utilities.gitPushTag("${GIT_TAG}", /*force*/ true)
 						}
 					}
 				}