[PATCH] setup: Only allow extenions.objectFormat to be specified once

["Eric W. Biederman" <ebiederm@gmail.com>]

Today there is no sanity checking of what happens when
extensions.objectFormat is specified multiple times.  Catch confused git
configurations by only allowing this option to be specified once.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 setup.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/setup.c b/setup.c
index 18927a847b86..ef9f79b8885e 100644
--- a/setup.c
+++ b/setup.c
@@ -580,6 +580,7 @@ static enum extension_result handle_extension(const char *var,
 	if (!strcmp(ext, "noop-v1")) {
 		return EXTENSION_OK;
 	} else if (!strcmp(ext, "objectformat")) {
+		struct string_list_item *item;
 		int format;
 
 		if (!value)
@@ -588,6 +589,13 @@ static enum extension_result handle_extension(const char *var,
 		if (format == GIT_HASH_UNKNOWN)
 			return error(_("invalid value for '%s': '%s'"),
 				     "extensions.objectformat", value);
+		/* Only support objectFormat being specified once. */
+		for_each_string_list_item(item, &data->v1_only_extensions) {
+			if (!strcmp(item->string, "objectformat"))
+				return error(_("'%s' already specified as '%s'"),
+					"extensions.objectformat",
+					hash_algos[data->hash_algo].name);
+		}
 		data->hash_algo = format;
 		return EXTENSION_OK;
 	}
-- 
2.41.0