eprintln init_logger failure (may need redir if it's flushed away)

and add a description on logging

docs/config_file.md

@@ -0,0 +1,37 @@
+## Config file
+
+- [Example](#example)
+- [Location](#location)
+- [Creating the file](#creating-the-file)
+
+### Example
+
+An example config can be found by running:
+
+```sh
+navi info config-example
+```
+
+You can also read it online by clicking [here](./config_file_example.yaml).
+
+### Location
+
+Run the following command to check where the config file is/should be located:
+
+```sh
+navi info config-path
+```
+
+### Creating the file
+
+Run the following command to generate a config file with the default parameters:
+
+```sh
+navi info config-example > "$(navi info config-path)"
+```
+
+### Logging
+
+The log file will be created under the same directory where the config locates.
+
+And you can use the `RUST_LOG` env to set the log level, e.g. `RUST_LOG=debug navi`.

src/bin/main.rs

@@ -24,8 +24,11 @@ impl FileAnIssue {
     }
 }
 
-fn main() -> Result<(), anyhow::Error> {
+fn main() -> anyhow::Result<()> {
-    init_logger()?;
+    if let Err(err) = init_logger() {
+        // may need redir stderr to a file to show this log initialization error
+        eprintln!("failed to initialize logging: {err:?}");
+    }
     navi::handle().map_err(|e| {
         error!("{e:?}");
         FileAnIssue::new(e).into()