submodule: reload HEAD/index after reading config
submodule: reload HEAD/index after reading config

Reload the HEAD and index data for a submodule after reading the
configuration.  The configuration may specify a `path`, so we must
update HEAD and index data with that path in mind.

saurabhsuniljain/libgit2,stewid/libgit2,leoyanggit/libgit2,KTXSoftware/libgit2,Corillian/libgit2,yongthecoder/libgit2,KTXSoftware/libgit2,joshtriplett/libgit2,joshtriplett/libgit2,jeffhostetler/public_libgit2,KTXSoftware/libgit2,Corillian/libgit2,saurabhsuniljain/libgit2,stewid/libgit2,stewid/libgit2,Tousiph/Demo1,leoyanggit/libgit2,jeffhostetler/public_libgit2,leoyanggit/libgit2,joshtriplett/libgit2,magnus98/TEST,joshtriplett/libgit2,Corillian/libgit2,Tousiph/Demo1,jeffhostetler/public_libgit2,Corillian/libgit2,Tousiph/Demo1,jeffhostetler/public_libgit2,saurabhsuniljain/libgit2,magnus98/TEST,KTXSoftware/libgit2,magnus98/TEST,KTXSoftware/libgit2,saurabhsuniljain/libgit2,yongthecoder/libgit2,magnus98/TEST,joshtriplett/libgit2,joshtriplett/libgit2,Tousiph/Demo1,saurabhsuniljain/libgit2,Corillian/libgit2,stewid/libgit2,magnus98/TEST,stewid/libgit2,jeffhostetler/public_libgit2,leoyanggit/libgit2,yongthecoder/libgit2,leoyanggit/libgit2,yongthecoder/libgit2,KTXSoftware/libgit2,jeffhostetler/public_libgit2,saurabhsuniljain/libgit2,leoyanggit/libgit2,magnus98/TEST,stewid/libgit2,yongthecoder/libgit2,Tousiph/Demo1,Corillian/libgit2,Tousiph/Demo1,yongthecoder/libgit2