From: =?UTF-8?q?Daniel=20Mart=C3=AD?= <mvdan@mvdan.cc>

secret_service_search_sync() can return an item whose secret is not
loaded, despite SECRET_SEARCH_LOAD_SECRETS being set: the search
silently discards secret-loading failures, and the GNOME keyring
daemon silently omits from its GetSecrets reply any item that is
locked or that was deleted after the search matched it, e.g. by a
concurrent "credential erase" from another git process.

secret_item_get_secret() then returns NULL, which we pass unchecked
to secret_value_get_text() and secret_value_unref(), producing

    secret_value_get_text: assertion 'value' failed
    secret_value_unref: assertion 'value != NULL' failed

and losing the password even when the secret is still retrievable.

Drop SECRET_SEARCH_LOAD_SECRETS and instead load the secret of the
one item we use with secret_item_load_secret_sync(), which does
report errors. A secret the search would have silently dropped is
now retrieved normally, and a genuinely inaccessible item produces
a useful message instead of assertion spew, with git falling back
to prompting either way. Merely guarding against NULL would avoid
the assertions, but would forfeit a secret that is still available.
The cost is unchanged: the search no longer batch-fetches the
secrets of all matching items, and the explicit load fetches the
one we use.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>

Submitted-As: https://lore.kernel.org/git/pull.2372.git.git.1785883217733.gitgitgadget@gmail.com