send-pack: factor out capability string generation

A run of 'var ? " var" : ""' fed to a long printf string in a deeply
nested block was hard to read.  Move it outside the loop and format
it into a strbuf.

As an added bonus, the trick to add "agent=<agent-name>" by using
two conditionals is replaced by a more readable version.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

send-pack.c

@@ -218,6 +218,7 @@ int send_pack(struct send_pack_args *args,
 	int in = fd[0];
 	int out = fd[1];
 	struct strbuf req_buf = STRBUF_INIT;
+	struct strbuf cap_buf = STRBUF_INIT;
 	struct ref *ref;
 	int new_refs;
 	int allow_deleting_refs = 0;
@@ -251,6 +252,15 @@ int send_pack(struct send_pack_args *args,
 		return 0;
 	}
 
+	if (status_report)
+		strbuf_addstr(&cap_buf, " report-status");
+	if (use_sideband)
+		strbuf_addstr(&cap_buf, " side-band-64k");
+	if (quiet_supported && (args->quiet || !args->progress))
+		strbuf_addstr(&cap_buf, " quiet");
+	if (agent_supported)
+		strbuf_addf(&cap_buf, " agent=%s", git_user_agent_sanitized());
+
 	/*
 	 * NEEDSWORK: why does delete-refs have to be so specific to
 	 * send-pack machinery that set_ref_status_for_push() cannot
@@ -279,18 +289,12 @@ int send_pack(struct send_pack_args *args,
 		} else {
 			char *old_hex = sha1_to_hex(ref->old_sha1);
 			char *new_hex = sha1_to_hex(ref->new_sha1);
-			int quiet = quiet_supported && (args->quiet || !args->progress);
 
 			if (!cmds_sent)
 				packet_buf_write(&req_buf,
-						 "%s %s %s%c%s%s%s%s%s",
+						 "%s %s %s%c%s",
 						 old_hex, new_hex, ref->name, 0,
-						 status_report ? " report-status" : "",
-						 use_sideband ? " side-band-64k" : "",
-						 quiet ? " quiet" : "",
-						 agent_supported ? " agent=" : "",
-						 agent_supported ? git_user_agent_sanitized() : ""
-						);
+						 cap_buf.buf);
 			else
 				packet_buf_write(&req_buf, "%s %s %s",
 						 old_hex, new_hex, ref->name);
@@ -311,6 +315,7 @@ int send_pack(struct send_pack_args *args,
 		packet_flush(out);
 	}
 	strbuf_release(&req_buf);
+	strbuf_release(&cap_buf);
 
 	if (use_sideband && cmds_sent) {
 		memset(&demux, 0, sizeof(demux));