$ git clone -n https://src.fedoraproject.org/rpms/btrfs-progs.git /var/lib/mock/f42-build-882148-184165/root/chroot_tmpdir/scmroot/btrfs-progs
Cloning into '/var/lib/mock/f42-build-882148-184165/root/chroot_tmpdir/scmroot/btrfs-progs'...
$ git fetch origin abd09d0c5a3302007e82deb23f3c08c09a93a832:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/btrfs-progs
 * [new ref]         abd09d0c5a3302007e82deb23f3c08c09a93a832 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at abd09d0 Update to 6.13 upstream release