new: scaffold new Debian source packages (non-interactive core)

src/changelog.rs

@@ -259,7 +259,13 @@ fn prepend_to_file(path: &Path, content: &str) -> Result<(), Box<dyn std::error:
     Ok(())
 }
 
-fn get_maintainer_info() -> Result<(String, String), Box<dyn std::error::Error>> {
+/// Discover the maintainer identity for changelog entries and package
+/// scaffolding: `$DEBFULLNAME`/`$DEBEMAIL` when both are set, else the git
+/// configuration (`user.name`/`user.email`).
+///
+/// Returns `(name, email)`, with a pointed error telling the user how to
+/// configure the missing piece.
+pub fn get_maintainer_info() -> Result<(String, String), Box<dyn std::error::Error>> {
     // From environment variables
     if let (Ok(name), Ok(email)) = (std::env::var("DEBFULLNAME"), std::env::var("DEBEMAIL")) {
         return Ok((name, email));