Merge branch 'jl/submodule-fetch-on-demand'
* jl/submodule-fetch-on-demand:
fetch/pull: Describe --recurse-submodule restrictions in the BUGS section
submodule update: Don't fetch when the submodule commit is already present
fetch/pull: Don't recurse into a submodule when commits are already present
Submodules: Add 'on-demand' value for the 'fetchRecurseSubmodule' option
config: teach the fetch.recurseSubmodules option the 'on-demand' value
fetch/pull: Add the 'on-demand' value to the --recurse-submodules option
fetch/pull: recurse into submodules when necessary
Conflicts:
builtin/fetch.c
submodule.c