Unable to build: fatal: transport 'file' not allowed

[obilodeau]

Following the instructions in the README, I arrive at:

flatpak-builder --user  --ccache --keep-build-dirs  --force-clean -v  --repo=/tmp/fb.repo fpbuilder net.syncthing.syncthing.yaml
[...]
FB: Running: git config submodule.test-data.url file:///home/obilodeau/Documents/src/me.kozec.syncthingtk/.flatpak-builder/git/https_github.com_maxmind_MaxMind-DB.git
FB: Running: git submodule update --init test-data
Cloning into '/home/obilodeau/Sync/src/me.kozec.syncthingtk/.flatpak-builder/build/syncthing-2/vendor/github.com/oschwald/geoip2-golang/test-data'...
fatal: transport 'file' not allowed
fatal: clone of 'file:///home/obilodeau/Documents/src/me.kozec.syncthingtk/.flatpak-builder/git/https_github.com_maxmind_MaxMind-DB.git' into submodule path '/home/obilodeau/Sync/src/me.kozec.syncthingtk/.flatpak-builder/build/syncthing-2/vendor/github.com/oschwald/geoip2-golang/test-data' failed
Failed to clone 'test-data'. Retry scheduled
Cloning into '/home/obilodeau/Sync/src/me.kozec.syncthingtk/.flatpak-builder/build/syncthing-2/vendor/github.com/oschwald/geoip2-golang/test-data'...
fatal: transport 'file' not allowed
fatal: clone of 'file:///home/obilodeau/Documents/src/me.kozec.syncthingtk/.flatpak-builder/git/https_github.com_maxmind_MaxMind-DB.git' into submodule path '/home/obilodeau/Sync/src/me.kozec.syncthingtk/.flatpak-builder/build/syncthing-2/vendor/github.com/oschwald/geoip2-golang/test-data' failed
Failed to clone 'test-data' a second time, aborting
Error: module syncthing: Child process exited with code 1
FB: Unmounting read-only fs: fusermount -uz /home/obilodeau/Documents/src/me.kozec.syncthingtk/.flatpak-builder/rofiles/rofiles-oZhrfS

oschwald/geoip2-golang 1.9.0 is trying to pull in that test-data submodule.

Any idea how can I fix this?

[obilodeau]

This looks like it is this bug: https://github.com/flatpak/flatpak-builder/issues/495