[PATCH 4/4] ident: do not ignore empty config name/email

[Jeff King <peff@peff.net>]

When we read user.name and user.email from a config file,
they go into strbufs. When a caller asks ident_default_name()
for the value, we fallback to auto-detecting if the strbuf
is empty.

That means that explicitly setting an empty string in the
config is identical to not setting it at all. This is
potentially confusing, as we usually accept a configured
value as the final value.

Signed-off-by: Jeff King <peff@peff.net>
---
This one is perhaps questionable. Maybe somebody is relying on setting a
per-repo user.name to override a ~/.gitconfig value and enforce
auto-detection?

 ident.c                       |  4 ++--
 t/t7518-ident-corner-cases.sh | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/ident.c b/ident.c
index ead09ff7f..c0364fe3a 100644
--- a/ident.c
+++ b/ident.c
@@ -153,7 +153,7 @@ static void copy_email(const struct passwd *pw, struct strbuf *email,
 
 const char *ident_default_name(void)
 {
-	if (!git_default_name.len) {
+	if (!(ident_config_given & IDENT_NAME_GIVEN) && !git_default_name.len) {
 		copy_gecos(xgetpwuid_self(&default_name_is_bogus), &git_default_name);
 		strbuf_trim(&git_default_name);
 	}
@@ -162,7 +162,7 @@ const char *ident_default_name(void)
 
 const char *ident_default_email(void)
 {
-	if (!git_default_email.len) {
+	if (!(ident_config_given & IDENT_MAIL_GIVEN) && !git_default_email.len) {
 		const char *email = getenv("EMAIL");
 
 		if (email && email[0]) {
diff --git a/t/t7518-ident-corner-cases.sh b/t/t7518-ident-corner-cases.sh
index 3d2560c3c..ef570ac62 100755
--- a/t/t7518-ident-corner-cases.sh
+++ b/t/t7518-ident-corner-cases.sh
@@ -22,4 +22,15 @@ test_expect_success 'commit rejects all-crud name' '
 		git commit --allow-empty -m foo
 '
 
+# We must test the actual error message here, as an unwanted
+# auto-detection could fail for other reasons.
+test_expect_success 'empty configured name does not auto-detect' '
+	(
+		sane_unset GIT_AUTHOR_NAME &&
+		test_must_fail \
+			git -c user.name= commit --allow-empty -m foo 2>err &&
+		test_i18ngrep "empty ident name" err
+	)
+'
+
 test_done
-- 
2.12.0.rc2.597.g959f68882