git-daemon: use LOG_PID, simplify logging code

Make git-daemon use LOG_PID like most daemons, instead of prepending the
pid to the message ourselves, when using syslog(3).

Simplify the logging code by setting stderr to line buffered, instead of
building a single string and writing it out with a single write(2).

Give an extra log message at the daemon start-up.
Signed-off-by: NStephen R. van den Berg <srb@cuci.nl>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

daemon.c

@@ -78,38 +78,19 @@ static struct interp interp_table[] = {
 
 static void logreport(int priority, const char *err, va_list params)
 {
-	/* We should do a single write so that it is atomic and output
-	 * of several processes do not get intermingled. */
-	char buf[1024];
-	int buflen;
-	int maxlen, msglen;
-
-	/* sizeof(buf) should be big enough for "[pid] \n" */
-	buflen = snprintf(buf, sizeof(buf), "[%ld] ", (long) getpid());
-
-	maxlen = sizeof(buf) - buflen - 1; /* -1 for our own LF */
-	msglen = vsnprintf(buf + buflen, maxlen, err, params);
-
 	if (log_syslog) {
+		char buf[1024];
+		vsnprintf(buf, sizeof(buf), err, params);
 		syslog(priority, "%s", buf);
-		return;
 	}
-
-	/* maxlen counted our own LF but also counts space given to
-	 * vsnprintf for the terminating NUL.  We want to make sure that
-	 * we have space for our own LF and NUL after the "meat" of the
-	 * message, so truncate it at maxlen - 1.
-	 */
-	if (msglen > maxlen - 1)
-		msglen = maxlen - 1;
-	else if (msglen < 0)
-		msglen = 0; /* Protect against weird return values. */
-	buflen += msglen;
-
-	buf[buflen++] = '\n';
-	buf[buflen] = '\0';
-
-	write_in_full(2, buf, buflen);
+	else {
+		/* Since stderr is set to linebuffered mode, the
+		 * logging of different processes will not overlap
+		 */
+		fprintf(stderr, "[%d] ", (int)getpid());
+		vfprintf(stderr, err, params);
+		fputc('\n', stderr);
+	}
 }
 
 static void logerror(const char *err, ...)
@@ -1178,9 +1159,11 @@ int main(int argc, char **argv)
 	}
 
 	if (log_syslog) {
-		openlog("git-daemon", 0, LOG_DAEMON);
+		openlog("git-daemon", LOG_PID, LOG_DAEMON);
 		set_die_routine(daemon_die);
 	}
+	else
+		setlinebuf(stderr); /* avoid splitting a message in the middle */
 
 	if (inetd_mode && (group_name || user_name))
 		die("--user and --group are incompatible with --inetd");
@@ -1233,8 +1216,10 @@ int main(int argc, char **argv)
 		return execute(peer);
 	}
 
-	if (detach)
+	if (detach) {
 		daemonize();
+		loginfo("Ready to rumble");
+	}
 	else
 		sanitize_stdfds();