Try not to duplicate license file metadata

#187

src/data.rs

@@ -35,20 +35,29 @@ pub(crate) fn generate_changelog_asset(options: &Config) -> CDResult<Option<Vec<
     }
 }
 
-/// Generates the copyright file from the license file and adds that to the tar archive.
-pub(crate) fn generate_copyright_asset(options: &Config) -> CDResult<Vec<u8>> {
-    let mut copyright: Vec<u8> = Vec::new();
-    writeln!(&mut copyright, "Upstream Name: {}", options.name)?;
+fn append_copyright_metadata(copyright: &mut Vec<u8>, options: &Config) -> Result<(), CargoDebError> {
+    writeln!(copyright, "Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/")?;
+    writeln!(copyright, "Upstream-Name: {}", options.name)?;
     if let Some(source) = options.repository.as_ref().or(options.homepage.as_ref()) {
-        writeln!(&mut copyright, "Source: {}", source)?;
+        writeln!(copyright, "Source: {}", source)?;
     }
-    writeln!(&mut copyright, "Copyright: {}", options.copyright)?;
+    writeln!(copyright, "Copyright: {}", options.copyright)?;
     if let Some(ref license) = options.license {
-        writeln!(&mut copyright, "License: {}", license)?;
+        writeln!(copyright, "License: {}", license)?;
     }
+    Ok(())
+}
+
+/// Generates the copyright file from the license file and adds that to the tar archive.
+pub(crate) fn generate_copyright_asset(options: &Config) -> CDResult<Vec<u8>> {
+    let mut copyright: Vec<u8> = Vec::new();
     if let Some(ref path) = options.license_file {
         let license_string = fs::read_to_string(options.path_in_workspace(path))
             .map_err(|e| CargoDebError::IoFile("unable to read license file", e, path.to_owned()))?;
+        if !has_copyright_metadata(&license_string) {
+            append_copyright_metadata(&mut copyright, options)?;
+        }
+
         // Skip the first `A` number of lines and then iterate each line after that.
         for line in license_string.lines().skip(options.license_file_skip_lines) {
             // If the line is a space, add a dot, else write the line.
@@ -59,12 +68,19 @@ pub(crate) fn generate_copyright_asset(options: &Config) -> CDResult<Vec<u8>> {
                 copyright.write_all(b"\n")?;
             }
         }
+    } else {
+        append_copyright_metadata(&mut copyright, options)?;
     }
 
     // Write a copy to the disk for the sake of obtaining a md5sum for the control archive.
     Ok(copyright)
 }
 
+fn has_copyright_metadata(file: &str) -> bool {
+    file.lines().take(10)
+        .any(|l| l.starts_with("License: ") || l.starts_with("Source: ") || l.starts_with("Upstream-Name: ") || l.starts_with("Format: "))
+}
+
 /// Compress man page assets per Debian Policy.
 ///
 /// # References

tests/command.rs

@@ -137,7 +137,7 @@ fn run_cargo_deb_command_on_example_dir_with_variant() {
     assert!(md5sums.contains("b1946ac92492d2347c6235b4d2611184  var/lib/example/1.txt\n"));
     assert!(md5sums.contains("591785b794601e212b260e25925636fd  var/lib/example/2.txt\n"));
     assert!(md5sums.contains("835a3c46f2330925774ebf780aa74241  var/lib/example/4.txt\n"));
-    assert!(md5sums.contains("f4b165c5ea1f9ec1b87abd72845627fd  usr/share/doc/example-debug/copyright\n"));
+    assert!(md5sums.contains("2455967cef930e647146a8c762199ed3  usr/share/doc/example-debug/copyright\n"));
 
     let ddir = TempDir::new("cargo-data-test").unwrap();
     assert!(Command::new("tar")
@@ -210,7 +210,7 @@ fn run_cargo_deb_command_on_example_dir_with_version() {
     assert!(md5sums.contains("b1946ac92492d2347c6235b4d2611184  var/lib/example/1.txt\n"));
     assert!(md5sums.contains("591785b794601e212b260e25925636fd  var/lib/example/2.txt\n"));
     assert!(md5sums.contains("1537684900f6b12358c88a612adf1049  var/lib/example/3.txt\n"));
-    assert!(md5sums.contains("4176f128e63dbe2f7ba37490bd0368db  usr/share/doc/example/copyright\n"));
+    assert!(md5sums.contains("4176f128e63dbe2f7ba37490bd0368db  usr/share/doc/example/copyright\n"), "has:\n{}", md5sums);
 
     let ddir = TempDir::new("cargo-data-test").unwrap();
     assert!(Command::new("tar")