All other error messages in cmd_update are reporting the submodule based
on its path, so let's do that for invalid update modes, too.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

The 'mode' variable is not used in cmd_update for its original purpose,
rename it to 'dummy' as it only serves the purpose to abort quickly
documenting this knowledge.

The variable 'stage' is also not used any more in cmd_update, so remove it.

This went unnoticed as first each function used the commonly used
submodule listing, which was converted in 74703a1 (submodule: rewrite
`module_list` shell function in C, 2015-09-02). When cmd_update was
using its own function starting in 4830868 (git submodule update:
have a dedicated helper for cloning, 2016-02-29), its removal was missed.

A later patch in this series also touches the communication between
the submodule helper and git-submodule.sh, but let's have this as
a preparatory patch, as it eases the next patch, which stores the
raw data instead of the line printed for this communication.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Separate the command line parsing from the actual execution of the command
within the repository. For now there is not a lot of execution as
most of it is still in git-submodule.sh.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

The information that is printed for update_submodules in
'submodule--helper update-clone' and consumed by 'git submodule update'
is stored as a string per submodule. This made sense at the time of
4830868 (git submodule update: have a dedicated helper for cloning,
2016-02-29), but as we want to migrate the rest of the submodule update
into C, we're better off having access to the raw information in a helper
struct.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

…dule

In a later patch we'll find this method handy.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

…worktree

e983175 (submodule: ensure core.worktree is set after update,
2018-06-18) was overly aggressive in calling connect_work_tree_and_git_dir
as that ensures both the 'core.worktree' configuration is set as well as
setting up correct gitlink file pointing at the git directory.

We do not need to check for the gitlink in this part of the cmd_update
in git-submodule.sh, as the initial call to update-clone will have ensured
that. So we can reduce the work to only (check and potentially) set the
'core.worktree' setting.

While at it move the check from shell to C as that proves to be useful in
a follow up patch, as we do not need the 'name' in shell now.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

This chews off a bit of the shell part of the update command in
git-submodule.sh. When writing the C code, keep in mind that the
submodule--helper part will go away eventually and we want to have
a C function that is able to determine the submodule update strategy,
it as a nicety, make determine_submodule_update_strategy accessible
for arbitrary repositories.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>