submodule update: add --remote for submodule's upstream changes

From: "W. Trevor King" <[email protected]>

Comments on v7 seem to have petered out, so here's v8. Changes since v7:

* Series based on gitster/master instead of v1.8.0.
* In Documentation/config.txt, restored trailing line of submodule.<name>.update documentation, which I had accidentally removed in v7.
* In Documentation/git-submodule.txt, make --no-fetch example in the --remote description more general, following Phil's suggestion.
* In git-submodule.sh:
* Remove accidental "ges" line.
* Use the submodule's default remote to determine which tracking branch to fetch. In v7 I'd been using the superproject's default remote.
* In cmd_add(), use sm_name instead of sm_path to store the --branch

    option (catching up with 73b0898).

W. Trevor King (3):
submodule: add get_submodule_config helper funtion submodule update: add --remote for submodule's upstream changes submodule add: If --branch is given, record it in .gitmodules

 Documentation/config.txt        |  6 +++++
 Documentation/git-submodule.txt | 25 +++++++++++++++++++-
 Documentation/gitmodules.txt    |  5 ++++
 git-submodule.sh                | 51 ++++++++++++++++++++++++++++++++++++++++-
 t/t7400-submodule-basic.sh      |  1 +
 t/t7406-submodule-update.sh     | 31 +++++++++++++++++++++++++
 6 files changed, 117 insertions(+), 2 deletions(-)

1.8.0