submodule: use absolute path for computing relative path connecting
The current caller of connect_work_tree_and_git_dir passes
an absolute path for the `git_dir` parameter. In the future patch
we will also pass in relative path for `git_dir`. Extend the functionality
of connect_work_tree_and_git_dir to take relative paths for parameters.
We could work around this in the future patch by computing the absolute
path for the git_dir in the calling site, however accepting relative
paths for either parameter makes the API for this function much harder
to misuse.
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>