Do not log to stderr by default

Jolly no longer logs to stderr to default. This cleans up the default
text that appears when running Jolly from the terminal.

docs/config.md

@@ -277,22 +277,21 @@ As a general rule, the jolly build script will warn if the
 # <a name="log"></a> [config.log]
 
 The `[config.log]` table contains settings that control error logging
-and debugging of Jolly. By default, Jolly will display error messages
-in the UI and print them to `stderr`, but this behavior can be
-customized.
+and debugging of Jolly. By default, Jolly does not perform any
+logging, but this behavior can be customized.
 
 **Important Note** *When you are trying to troubleshoot a bug in
-Jolly, you may be asked to supply logfiles from operating
-Jolly. Please be aware that at higher log levels, Jolly will include
-the Jolly entry targets, and whichever text was entered in the search
-window. This may be considered sensitive information and you should
-always review logs before sharing them.*
+Jolly, you may be asked to supply logfiles. Please be aware that at
+higher log levels, Jolly will include the Jolly entry targets, and
+whichever text was entered in the search window. This may be
+considered sensitive information and you should always review logs
+before sharing them.*
 
 To customize behavior, use the following fields:
 
 | field name | data type                  | description                                                                                                                              |
 |------------|----------------------------|------------------------------------------------------------------------------------------------------------------------------------------|
-| `file`     | *string*                   | Additional filename to write logs to. Always appends.                                                                                    |
+| `file`     | *string*                   | Filename to write logs to. Always appends. Can be `'stdout'` or `'stderr'` to write to that stream                                       |
 | `filters`  | *string* OR *string array* | [env_logger](https://docs.rs/env_logger/latest/env_logger/index.html#enabling-logging) filters for logging, by default, only log `error` |
 
 
@@ -314,8 +313,11 @@ filters = ["jolly=debug", "cosmic_text=trace"]
 
 Specify a filename for Jolly to write logs to. If the file cannot be
 accessed then an error is returned. Jolly will always append to this
-file if it already exists. Jolly will also continue to write trace
-messages to `stderr`.
+file if it already exists.
+
+Jolly treats a file named `'stderr'` `'stdout'` as special: If file is
+set to one of these values, it will write to the corresponding stream.
+
 
 ## `filters`        &mdash; *string* OR *string array*
 

src/log.rs

@@ -14,26 +14,38 @@ pub struct LogSettings {
 
 impl LogSettings {
     pub fn init_logger(&self) -> Result<(), error::Error> {
-        self.build_logger().map(|mut b| b.init())
+        self.build_logger().map(|b| {
+            if let Some(mut b) = b {
+                b.init()
+            }
+        })
     }
 
-    fn build_logger(&self) -> Result<Builder, error::Error> {
+    fn build_logger(&self) -> Result<Option<Builder>, error::Error> {
+        use env_logger::fmt::Target;
+
         let mut builder = Builder::new();
         builder
             .parse_filters(&self.filters.join(","))
-            .format_timestamp_micros()
-            .target(env_logger::fmt::Target::Stderr);
+            .format_timestamp_micros();
 
-        if let Some(fname) = &self.file {
-            let f = std::fs::OpenOptions::new()
-                .append(true)
-                .create(true)
-                .open(fname)
-                .map_err(|e| error::Error::IoError(self.file.clone(), e))?;
-            builder.target(env_logger::fmt::Target::Pipe(Box::new(f)));
+        if let Some(filename) = &self.file {
+            if filename == "stdout" {
+                builder.target(Target::Stdout);
+            } else if filename == "stderr" {
+                builder.target(Target::Stderr);
+            } else {
+                let f = std::fs::OpenOptions::new()
+                    .append(true)
+                    .create(true)
+                    .open(filename)
+                    .map_err(|e| error::Error::IoError(self.file.clone(), e))?;
+                builder.target(env_logger::fmt::Target::Pipe(Box::new(f)));
+            }
+            Ok(Some(builder))
+        } else {
+            Ok(None)
         }
-
-        Ok(builder)
     }
 }
 
@@ -52,6 +64,7 @@ mod tests {
             filters: vec!["trace".into()],
         }
         .build_logger()
+        .map(Option::unwrap)
     }
 
     #[test]