From: Koji Nakamaru <koji.nakamaru@gree.net>

Resolves "failed to store: -25299" when "fetch.parallel 0" is configured
and there are many submodules.

The error code -25299 (errSecDuplicateItem) may be returned by
SecItemUpdate() in add_internet_password() if multiple instances of
git-credential-osxkeychain run in parallel. This patch introduces an
exclusive lock to serialize execution for avoiding this and other
potential issues.

Signed-off-by: Koji Nakamaru <koji.nakamaru@gree.net>

Submitted-As: https://lore.kernel.org/git/pull.1729.git.1715328467099.gitgitgadget@gmail.com