micro-revision and source sha1sums do not work when not building in the source tree.
configure allows you to build your binaries in a dedicated build tree instead of polluting the source tree with binary droppings.
i.e. mkdir build-tree && cd $_ && /configure && make
Tor's Makefiles create src/common/common_sha1.i, src/or/micro-revision.i and src/or/or_sha1.i from source files, however the makefiles do not handle the build-tree != source-tree case correctly.