Function add_lore_fetch_refspec 

pub fn add_lore_fetch_refspec(
    repo: &Path,
    remote: &str,
) -> Result<(), SyncError>

Adds a tracking-namespace lore fetch refspec to a remote’s config (opt-in).

Configures +refs/lore/*:refs/lore/remotes/<remote>/* so a plain git pull safely pre-populates the remote-tracking refs without force-moving the live local refs/lore/*. The real merge into the local ref still happens through lore sync; fetching into the live ref directly would bypass the merge model and could make an unpushed local lore commit unreachable.

The operation is idempotent: if the tracking-namespace refspec is already configured, nothing changes. An older +refs/lore/*:refs/lore/* entry written by a previous build is migrated in place (removed, not duplicated) so plain fetches stop clobbering the local ref.