Store the previous release as a property in the parent

Currently we only have the information about the current release name
but at some places the version of the previous one would be useful.

This adds a new property 'previousReleaseVersion' to contain the
necessary information and is updated by the prepare-release workflow.

.github/workflows/prepareRelease.yml

@@ -31,10 +31,17 @@ jobs:
         java-version: '17'
         distribution: 'temurin'
         cache: maven
+    - name: Store Current Version
+      id: get-current-release
+      run: |
+           mvn help:evaluate -Dexpression=releaseNumberSDK --quiet '-Doutput=releaseNumberSDK-value.txt'
+           streamVersion=$(<releaseNumberSDK-value.txt)
+           rm -f releaseNumberSDK-value.txt
+           echo "version=$(streamVersion)" >> $GITHUB_OUTPUT
     - name: Update Main Versions
       run: mvn -U -ntp -f eclipse-platform-parent org.eclipse.tycho:tycho-versions-plugin:set-version -DnewVersion=${{ github.event.milestone.title }}.0-SNAPSHOT -Dmodules=../eclipse.platform.releng.prereqs.sdk
     - name: Update Release Versions
-      run: mvn -ntp -f eclipse-platform-parent/pom.xml --non-recursive org.eclipse.tycho:tycho-versions-plugin:set-property -Dproperties=releaseVersion,releaseName -DnewReleaseName=${{ steps.get-release-name.outputs.name }} -DnewreleaseVersion=${{ github.event.milestone.title }}
+      run: mvn -ntp -f eclipse-platform-parent/pom.xml --non-recursive org.eclipse.tycho:tycho-versions-plugin:set-property -Dproperties=releaseVersion,releaseName,previousReleaseVersion -DnewPreviousReleaseVersion=${{ steps.get-current-release.outputs.version }} -DnewReleaseName=${{ steps.get-release-name.outputs.name }} -DnewreleaseVersion=${{ github.event.milestone.title }}
     - name: Create Pull Request for Release ${{ github.event.milestone.title }}
       uses: peter-evans/create-pull-request@5e914681df9dc83aa4e4905692ca88beb2f9e91f # v7.0.5
       with:

eclipse-platform-parent/pom.xml

@@ -51,6 +51,7 @@
     -->
     <releaseName>2025-03</releaseName>
     <releaseVersion>4.35</releaseVersion>
+    <previousReleaseVersion>4.34</previousReleaseVersion>
     <!--
       The releaseNumbers below, for SDK and Platform, might be
       thought of as the "marketing number" or "branding number",

eclipse.platform.releng.tychoeclipsebuilder/eclipse-junit-tests/src/main/resources/label.properties

@@ -5,4 +5,4 @@ buildId=${buildId}
 # such as "4.5" instead of "4.5.0".
 eclipseStream=${releaseNumberSDK}
 # similar for previous release version
-previousReleaseVersion=4.34RC2
+previousReleaseVersion=${previousReleaseVersion}RC2