contrib/credential: fix compiling "libsecret" helper
The "libsecret" credential helper does not compile when developer warnings are enabled due to three warnings: - contrib/credential/libsecret/git-credential-libsecret.c:78:1: missing initializer for field ‘reserved’ of ‘SecretSchema’ [-Werror=missing-field-initializers]. This issue is fixed by using designated initializers. - contrib/credential/libsecret/git-credential-libsecret.c:171:43: comparison of integer expressions of different signedness: ‘int’ and ‘guint’ {aka ‘unsigned int’} [-Werror=sign-compare]. This issue is fixed by using an unsigned variable to iterate through the string vector. - contrib/credential/libsecret/git-credential-libsecret.c:420:14: unused parameter ‘argc’ [-Werror=unused-parameter]. This issue is fixed by checking the number of arguments, but in the least restrictive way possible. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>