Fix long filenames when creating tar header from metadata and filename

rather than path

tar/src/header.rs

@@ -281,6 +281,21 @@ impl Header {
         owner: Option<Owner>,
     ) -> Result<Self, Error> {
         let mut header = Header::default();
+        let (filename, prefix) = if filename.len() < 100 {
+            (filename.to_string(), None)
+        } else {
+            // Deal with file names longer than 100 bytes
+            let path = PathBuf::from(&filename);
+            let name = match path.file_name().and_then(|n| n.to_str()) {
+                Some(n) => n.to_string(),
+                None => return Err(Error::Io(io::Error::new(io::ErrorKind::Other, "Cannot get file name"))),
+            };
+            let dir = match path.parent() {
+                Some(d) => d,
+                None => return Err(Error::Io(io::Error::new(io::ErrorKind::Other, "Cannot get path prefix"))),
+            };
+            (name, Some(format!("{}", dir.display())))
+        };
         header.fname[..filename.len()].copy_from_slice(filename.as_bytes());
         let mode = format!("{:07o}", meta.st_mode());
         header.mode[..mode.len()].copy_from_slice(mode.as_bytes());
@@ -301,6 +316,9 @@ impl Header {
         header.size[..size.len()].copy_from_slice(size.as_bytes());
         let mtime = format!("{:011o}", meta.st_mtime());
         header.mtime[..mtime.len()].copy_from_slice(mtime.as_bytes());
+        if let Some(prefix) = prefix {
+            header.file_prefix[..prefix.len()].copy_from_slice(prefix.as_bytes());
+        }
         header.link_indicator[0] = FileType::from(meta) as u8;
         if header.link_indicator[0] == FileType::Symlink as u8 {
             let link = fs::read_link(filename)?.to_str().unwrap().to_string();