deb: cross-compilation, ephemeral contexts, local builds

Multiple changes:
- New contexts (schroot, unshare)
- Cross-building quirks, with ephemeral contexts and repositories management
- Contexts with parents, global context manager, better lifetime handling
- Local building of binary packages
- Pull: pulling dsc files by default
- Many small bugfixes and changes

Co-authored-by: Valentin Haudiquet <valentin.haudiquet@canonical.com>
Co-committed-by: Valentin Haudiquet <valentin.haudiquet@canonical.com>

src/pull.rs

@@ -262,22 +262,51 @@ async fn fetch_orig_tarball(
     Ok(())
 }
 
+async fn fetch_dsc_file(
+    info: &PackageInfo,
+    cwd: Option<&Path>,
+    progress: ProgressCallback<'_>,
+) -> Result<(), Box<dyn Error>> {
+    let target_dir = cwd.unwrap_or_else(|| Path::new("."));
+
+    // Find the dsc file in the file list
+    let dsc_file = info
+        .stanza
+        .files
+        .iter()
+        .find(|f| f.name.ends_with(".dsc"))
+        .ok_or("Could not find .dsc file in package info")?;
+    let filename = &dsc_file.name;
+
+    debug!("Fetching dsc file: {}", filename);
+
+    download_file_checksum(
+        format!("{}/{}", &info.archive_url, filename).as_str(),
+        &dsc_file.sha256,
+        target_dir,
+        progress,
+    )
+    .await?;
+
+    Ok(())
+}
+
 async fn fetch_archive_sources(
     info: &PackageInfo,
     cwd: Option<&Path>,
     progress: ProgressCallback<'_>,
 ) -> Result<(), Box<dyn Error>> {
     let package_dir = if let Some(path) = cwd {
-        path.join(&info.stanza.package)
+        path
     } else {
-        Path::new(&info.stanza.package).to_path_buf()
+        &Path::new(".").to_path_buf()
     };
 
-    std::fs::create_dir_all(&package_dir)?;
+    std::fs::create_dir_all(package_dir)?;
 
     for file in &info.stanza.files {
         let url = format!("{}/{}", info.archive_url, file.name);
-        download_file_checksum(&url, &file.sha256, &package_dir, progress).await?;
+        download_file_checksum(&url, &file.sha256, package_dir, progress).await?;
     }
 
     // Extract the debian tarball or diff
@@ -399,6 +428,7 @@ pub async fn pull(
                 0,
             );
         }
+
         clone_repo(
             url.as_str(),
             package,
@@ -406,6 +436,7 @@ pub async fn pull(
             Some(&package_dir),
             progress,
         )?;
+
         if !package_info.is_native() {
             if let Some(cb) = progress {
                 cb("Fetching orig tarball...", "", 0, 0);
@@ -414,12 +445,17 @@ pub async fn pull(
         } else {
             debug!("Native package, skipping orig tarball fetch.");
         }
+
+        if let Some(cb) = progress {
+            cb("Fetching dsc file...", "", 0, 0);
+        }
+        fetch_dsc_file(&package_info, Some(&package_dir), progress).await?;
     } else {
         // Fallback to archive fetching
         if let Some(cb) = progress {
             cb("Downloading from archive...", "", 0, 0);
         }
-        fetch_archive_sources(&package_info, Some(cwd.unwrap_or(Path::new("."))), progress).await?;
+        fetch_archive_sources(&package_info, Some(&package_dir), progress).await?;
     }
 
     Ok(package_info)
@@ -480,18 +516,25 @@ mod tests {
             }
         }
 
-        // Check for orig tarball in package dir
+        // Check for orig tarball in package dir (only for non-native packages)
         let mut found_tarball = false;
+        let mut found_dsc = false;
         for entry in std::fs::read_dir(package_dir).unwrap() {
             let entry = entry.unwrap();
             let name = entry.file_name().to_string_lossy().to_string();
             if name.contains(".orig.tar.") {
                 found_tarball = true;
-                break;
+            }
+            if name.ends_with(".dsc") {
+                found_dsc = true;
             }
         }
 
-        assert!(found_tarball, "Orig tarball not found in package dir");
+        // Only check for orig tarball if the package is not native
+        if !info.is_native() {
+            assert!(found_tarball, "Orig tarball not found in package dir");
+        }
+        assert!(found_dsc, "DSC file not found in package dir");
     }
 
     #[tokio::test]