config: teach "git -c" to recognize an empty string

In a config file, you can do:

  [foo]
  bar

to turn the "foo.bar" boolean flag on, and you can do:

  [foo]
  bar=

to set "foo.bar" to the empty string. However, git's "-c"
parameter treats both:

  git -c foo.bar

and

  git -c foo.bar=

as the boolean flag, and there is no way to set a variable
to the empty string. This patch enables the latter form to
do that.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/t/t1300-repo-config.sh b/t/t1300-repo-config.sh
index 967359344..38917da0e 100755
--- a/t/t1300-repo-config.sh
+++ b/t/t1300-repo-config.sh
@@ -1006,6 +1006,17 @@ test_expect_success 'git -c "key=value" support' '
 	test_must_fail git -c name=value config core.name
 '
 
+# We just need a type-specifier here that cares about the
+# distinction internally between a NULL boolean and a real
+# string (because most of git's internal parsers do care).
+# Using "--path" works, but we do not otherwise care about
+# its semantics.
+test_expect_success 'git -c can represent empty string' '
+	echo >expect &&
+	git -c foo.empty= config --path foo.empty >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'key sanity-checking' '
 	test_must_fail git config foo=bar &&
 	test_must_fail git config foo=.bar &&