new: keep generated builds away from local build outputs and vendored autotools files

src/new/debian.rs

@@ -107,9 +107,19 @@ fn source_format(opts: &NewOptions) -> OutputFile {
 
 /// `debian/source/local-options` with `single-debian-patch`, so later
 /// upstream-tree edits stay representable as one `debian/patches/debian-changes-*`
-/// patch instead of failing the build (quilt only).
+/// patch instead of failing the build (quilt only). Common build-output
+/// directories are excluded from the delta as well: compiling locally before
+/// a source build must not turn `target/`, `node_modules/` or `.venv/`
+/// binaries into unrepresentable changes (dpkg ignores `__pycache__` and
+/// friends by default, but not those).
 fn local_options() -> OutputFile {
-    OutputFile::new("debian/source/local-options", "single-debian-patch\n")
+    OutputFile::new(
+        "debian/source/local-options",
+        "single-debian-patch\n\
+         extend-diff-ignore = ^target/\n\
+         extend-diff-ignore = ^node_modules/\n\
+         extend-diff-ignore = ^\\.venv/\n",
+    )
 }
 
 /// `debian/changelog`: the single initial entry, distribution UNRELEASED by
@@ -558,7 +568,10 @@ mod tests {
         assert_eq!(find("debian/source/format").contents, "3.0 (quilt)\n");
         assert_eq!(
             find("debian/source/local-options").contents,
-            "single-debian-patch\n"
+            "single-debian-patch\n\
+             extend-diff-ignore = ^target/\n\
+             extend-diff-ignore = ^node_modules/\n\
+             extend-diff-ignore = ^\\.venv/\n"
         );
 
         let native = NewOptions {