appender: add fallback to file creation date

When using the linux-musl target for rust, the file creation time
cannot be retrieved, as the current version does not support it yet (
This will be fixed with [0]). In the meantime, we parse the datetime
from the filename and use that as a fallback.

Fixes: #2999

[0]: rust-lang/rust#125692

tracing-appender/src/rolling.rs

@@ -34,7 +34,7 @@ use std::{
     path::{Path, PathBuf},
     sync::atomic::{AtomicUsize, Ordering},
 };
-use time::{format_description, Date, Duration, OffsetDateTime, Time};
+use time::{format_description, Date, Duration, OffsetDateTime, PrimitiveDateTime, Time};
 
 mod builder;
 pub use builder::{Builder, InitError};
@@ -602,7 +602,24 @@ impl Inner {
                     return None;
                 }
 
-                let created = metadata.created().ok()?;
+                let created = metadata.created().ok().or_else(|| {
+                    let datetime = if self.log_filename_prefix.is_none() {
+                        PrimitiveDateTime::parse(
+                            filename.split('.').collect::<Vec<&str>>()[0],
+                            &self.date_format,
+                        )
+                        .ok()?
+                        .assume_utc()
+                    } else {
+                        PrimitiveDateTime::parse(
+                            filename.split('.').collect::<Vec<&str>>()[1],
+                            &self.date_format,
+                        )
+                        .ok()?
+                        .assume_utc()
+                    };
+                    Some(datetime.into())
+                })?;
                 Some((entry, created))
             })
             .collect::<Vec<_>>()