server_supports_v2(): use a separate function for die_on_error

The server_supports_v2() helper lets a caller find out if the server
supports a feature, and will optionally die if it's not supported. This
makes the return value confusing, as it's only meaningful when the
function is not asked to die.

Coverity flagged a new call like:

  /* check that we support "foo" */
  server_supports_v2("foo", 1);

complaining that we usually checked the return value, but this time we
didn't. But this call is correct, and other ones that did:

  if (server_supports_v2("foo", 1))
          do_something_with_foo();

are "wrong", in the sense that we know the conditional will always be
true (but there's no bug; the code is simply misleading).

Let's split the "die" behavior into its own function which returns void,
and modify each caller to use the correct one.

Signed-off-by: Jeff King <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: peff

connect.c

@@ -66,7 +66,7 @@ static NORETURN void die_initial_contact(int unexpected)
 }
 
 /* Checks if the server supports the capability 'c' */
-int server_supports_v2(const char *c, int die_on_error)
+int server_supports_v2(const char *c)
 {
 	int i;
 
@@ -76,11 +76,13 @@ int server_supports_v2(const char *c, int die_on_error)
 		    (!*out || *out == '='))
 			return 1;
 	}
+	return 0;
+}
 
-	if (die_on_error)
+void ensure_server_supports_v2(const char *c)
+{
+	if (!server_supports_v2(c))
 		die(_("server doesn't support '%s'"), c);
-
-	return 0;
 }
 
 int server_feature_v2(const char *c, const char **v)
@@ -477,7 +479,7 @@ static void send_capabilities(int fd_out, struct packet_reader *reader)
 {
 	const char *hash_name;
 
-	if (server_supports_v2("agent", 0))
+	if (server_supports_v2("agent"))
 		packet_write_fmt(fd_out, "agent=%s", git_user_agent_sanitized());
 
 	if (server_feature_v2("object-format", &hash_name)) {
@@ -504,17 +506,18 @@ struct ref **get_remote_refs(int fd_out, struct packet_reader *reader,
 		&transport_options->unborn_head_target : NULL;
 	*list = NULL;
 
-	if (server_supports_v2("ls-refs", 1))
-		packet_write_fmt(fd_out, "command=ls-refs\n");
+	ensure_server_supports_v2("ls-refs");
+	packet_write_fmt(fd_out, "command=ls-refs\n");
 
 	/* Send capabilities */
 	send_capabilities(fd_out, reader);
 
-	if (server_options && server_options->nr &&
-	    server_supports_v2("server-option", 1))
+	if (server_options && server_options->nr) {
+		ensure_server_supports_v2("server-option");
 		for (i = 0; i < server_options->nr; i++)
 			packet_write_fmt(fd_out, "server-option=%s",
 					 server_options->items[i].string);
+	}
 
 	packet_delim(fd_out);
 	/* When pushing we don't want to request the peeled tags */

connect.h

@@ -20,7 +20,8 @@ enum protocol_version discover_version(struct packet_reader *reader);
 
 int server_supports_hash(const char *desired, int *feature_supported);
 const char *parse_feature_value(const char *feature_list, const char *feature, int *lenp, int *offset);
-int server_supports_v2(const char *c, int die_on_error);
+int server_supports_v2(const char *c);
+void ensure_server_supports_v2(const char *c);
 int server_feature_v2(const char *c, const char **v);
 int server_supports_feature(const char *c, const char *feature,
 			    int die_on_error);

fetch-pack.c

@@ -1317,15 +1317,15 @@ static void write_fetch_command_and_capabilities(struct strbuf *req_buf,
 {
 	const char *hash_name;
 
-	if (server_supports_v2("fetch", 1))
-		packet_buf_write(req_buf, "command=fetch");
-	if (server_supports_v2("agent", 0))
+	ensure_server_supports_v2("fetch");
+	packet_buf_write(req_buf, "command=fetch");
+	if (server_supports_v2("agent"))
 		packet_buf_write(req_buf, "agent=%s", git_user_agent_sanitized());
-	if (advertise_sid && server_supports_v2("session-id", 0))
+	if (advertise_sid && server_supports_v2("session-id"))
 		packet_buf_write(req_buf, "session-id=%s", trace2_session_id());
-	if (server_options && server_options->nr &&
-	    server_supports_v2("server-option", 1)) {
+	if (server_options && server_options->nr) {
 		int i;
+		ensure_server_supports_v2("server-option");
 		for (i = 0; i < server_options->nr; i++)
 			packet_buf_write(req_buf, "server-option=%s",
 					 server_options->items[i].string);