Unify console and file logback patterns

Update the file log pattern to write the thread name after the `---`
separator. The allows both file and console logs to be parsed in the
same way.

Fixes gh-2136

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -734,6 +734,7 @@ The following items are output:
 * Log Level -- `ERROR`, `WARN`, `INFO`, `DEBUG` or `TRACE`.
 * Process ID.
 * A `---` separator to distinguish the start of actual log messages.
+* Thread name -- Enclosed in square brackets (may be truncated for console output).
 * Logger name -- This is usually the source class name (often abbreviated).
 * The log message.
 

spring-boot/src/main/java/org/springframework/boot/logging/logback/DefaultLogbackConfiguration.java

@@ -46,7 +46,7 @@ class DefaultLogbackConfiguration {
 			+ "%clr(:){faint} %m%n%wex";
 
 	private static final String FILE_LOG_PATTERN = "%d{yyyy-MM-dd HH:mm:ss.SSS} %5p "
-			+ "${PID:- } [%t] --- %-40.40logger{39} : %m%n%wex";
+			+ "${PID:- } --- [%t] %-40.40logger{39} : %m%n%wex";
 
 	private static final Charset UTF8 = Charset.forName("UTF-8");
 

spring-boot/src/main/resources/org/springframework/boot/logging/logback/defaults.xml

@@ -10,7 +10,7 @@ initialization performed by Boot
 	<conversionRule conversionWord="wex" converterClass="org.springframework.boot.logging.logback.WhitespaceThrowableProxyConverter" />
 
 	<property name="CONSOLE_LOG_PATTERN" value="%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %clr(%5p) %clr(${PID:- }){magenta} %clr(---){faint} %clr([%15.15t{14}]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n%wex"/>
-	<property name="FILE_LOG_PATTERN" value="%d{yyyy-MM-dd HH:mm:ss.SSS} %5p ${PID:- } [%t] --- %-40.40logger{39} : %m%n%wex"/>
+	<property name="FILE_LOG_PATTERN" value="%d{yyyy-MM-dd HH:mm:ss.SSS} %5p ${PID:- } --- [%t] %-40.40logger{39} : %m%n%wex"/>
 
 	<appender name="DEBUG_LEVEL_REMAPPER" class="org.springframework.boot.logging.logback.LevelRemappingAppender">
 		<destinationLogger>org.springframework.boot</destinationLogger>