That branch is not based on anything in the Sage history, it is a separate root. I think Andrew's plugin doesn't take care of that case:
$ git checkout 72c453830846583dbfdf2cae224df776ef38ea26
HEAD is now at 72c4538... add more autotools executables
$ git ls-files
build/pkgs/autotools/Makefile.build
build/pkgs/autotools/SPKG.txt
build/pkgs/autotools/autofoo
build/pkgs/autotools/checksums.ini
build/pkgs/autotools/install-info.exe.manifest
build/pkgs/autotools/latest_version
build/pkgs/autotools/package-version.txt
build/pkgs/autotools/patches/m4-no-gets.patch
build/pkgs/autotools/spkg-install
build/pkgs/autotools/spkg-write-makefile
build/pkgs/autotools/version-list
$ git log --oneline
72c4538 add more autotools executables
7cc6067 autotools: spkg (#15123)
b1f08de Trac #13557: update the autotools spkg, add Texinfo
7332219 Trac #13357: initial version