Allow toggling parts of the default format (#66)

* allow toggling parts of the default format

* add a from_default_env method and docs

Author: KodrAus

examples/custom_default_format.rs

@@ -0,0 +1,44 @@
+/*!
+Disabling parts of the default format.
+
+Before running this example, try setting the `MY_LOG_LEVEL` environment variable to `info`:
+
+```no_run,shell
+$ export MY_LOG_LEVEL='info'
+```
+
+Also try setting the `MY_LOG_STYLE` environment variable to `never` to disable colors
+or `auto` to enable them:
+
+```no_run,shell
+$ export MY_LOG_STYLE=never
+```
+
+If you want to control the logging output completely, see the `custom_logger` example.
+*/
+
+#[macro_use]
+extern crate log;
+extern crate env_logger;
+
+use env_logger::{Env, Builder};
+
+fn init_logger() {
+    let env = Env::default()
+        .filter("MY_LOG_LEVEL")
+        .write_style("MY_LOG_STYLE");
+
+    let mut builder = Builder::from_env(env);
+
+    builder
+        .default_format_level(false)
+        .default_format_timestamp(false);
+
+    builder.init();
+}
+
+fn main() {
+    init_logger();
+
+    info!("a log from `MyLogger`");
+}

examples/custom_logger.rs

@@ -7,13 +7,6 @@ Before running this example, try setting the `MY_LOG_LEVEL` environment variable
 $ export MY_LOG_LEVEL='info'
 ```
 
-Also try setting the `MY_LOG_STYLE` environment variable to `never` to disable colors
-or `auto` to enable them:
-
-```no_run,shell
-$ export MY_LOG_STYLE=never
-```
-
 If you only want to change the way logs are formatted, look at the `custom_format` example.
 */
 

examples/default.rs

@@ -19,8 +19,14 @@ $ export MY_LOG_STYLE=never
 extern crate log;
 extern crate env_logger;
 
+use env_logger::Env;
+
 fn main() {
-    env_logger::init_from_env("MY_LOG_LEVEL");
+    let env = Env::default()
+        .filter("MY_LOG_LEVEL")
+        .write_style("MY_LOG_STYLE");
+
+    env_logger::init_from_env(env);
 
     trace!("some trace log");
     debug!("some debug log");