[Build] Update submodules to remote tip only on non-maintenance branches

[HannesWell]

This prevents maintenance branches from fetching the latest changes on the master branches of all submodules and therefore failing all builds early (because the sub-module expect a newer parent-pom version).

The multi-branch pipeline of this repo must then be configured to not have Update tracking submodules to tip of branch enabled.

Follow-up on:

• [Build] Use latest commit of branch specified in .gitmodules file #3000

[HannesWell]

Another alternative might be to update the .gitmodules file on the maintenance branch and set that maintenance branch as submodule-branch, instead of master, similar to how it's done with the
cje-production/streams/repositories_master.txt (which is renamed) or cje-production/streams/repositories_java25.txt file, e.g. in

• Move 4.37-I builds to R4_37_maintenance branch #3272

The repositories_master.txt wouldn't then be necessary anymore and repositories_java25.txt could only contain the branches that are different from .gitmodules (which would also reduce the RelEng changes). This might also allow us to simplify

eclipse.platform.releng.aggregator/cje-production/mbscripts/mb100_cloneRepos.sh

Line 30 in 9eda991

git submodule foreach 'git fetch; SUBMODULE_BRANCH=$(grep $name: ../../../streams/repositories_$PATCH_OR_BRANCH_LABEL.txt | cut -f2 -d\ ); SUBMODULE_BRANCH=${SUBMODULE_BRANCH:-$BRANCH}; echo Checking out $SUBMODULE_BRANCH; git checkout $SUBMODULE_BRANCH; git pull'

and

eclipse.platform.releng.aggregator/cje-production/mbscripts/mb110_tagBuildInputs.sh

Line 78 in 9eda991

git submodule foreach 'if grep "^${name}:" ../../../streams/repositories_$PATCH_OR_BRANCH_LABEL.txt > /dev/null; then git tag $BUILD_ID; PUSH_URL="$(toPushRepo $(git config --get remote.origin.url))"; git push --verbose $PUSH_URL $BUILD_ID; else echo Skipping $name; fi || :'

But as this is more work to implement, I would leave that for later.

[HannesWell]

The multi-branch pipeline of this repo must then be configured to not have Update tracking submodules to tip of branch enabled.

I have already disabled that option in the configuration of this repos Jenkins multi-branch pipeline project and it seems to work as desired. A PR to the 4.37_maintenance branch can have a successful build:

• [Build] Use Tycho 5 release on R4_37_maintenance #3309