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/deb/local.rs

@@ -0,0 +1,171 @@
+/// Local binary package building
+/// Directly calling 'debian/rules' in current context
+use crate::context;
+use crate::deb::find_dsc_file;
+use std::collections::HashMap;
+use std::error::Error;
+use std::path::Path;
+
+use crate::deb::cross;
+
+pub fn build(
+    package: &str,
+    version: &str,
+    arch: &str,
+    series: &str,
+    build_root: &str,
+    cross: bool,
+) -> Result<(), Box<dyn Error>> {
+    // Environment
+    let mut env = HashMap::<String, String>::new();
+    env.insert("LANG".to_string(), "C".to_string());
+    env.insert("DEBIAN_FRONTEND".to_string(), "noninteractive".to_string());
+
+    let ctx = context::current();
+
+    if cross {
+        log::debug!("Setting up environment for local cross build...");
+        cross::setup_environment(&mut env, arch)?;
+        cross::ensure_repositories(arch, series)?;
+    }
+
+    // Update package lists
+    log::debug!("Updating package lists for local build...");
+    let status = ctx
+        .command("apt-get")
+        .envs(env.clone())
+        .arg("update")
+        .status()?;
+    if !status.success() {
+        return Err(
+            "Could not execute apt-get update. If this is a local build, try executing with sudo."
+                .into(),
+        );
+    }
+
+    // Install essential packages
+    log::debug!("Installing essential packages for local build...");
+    let mut cmd = ctx.command("apt-get");
+
+    cmd.envs(env.clone())
+        .arg("-y")
+        .arg("install")
+        .arg("build-essential")
+        .arg("dose-builddebcheck")
+        .arg("fakeroot");
+    if cross {
+        cmd.arg(format!("crossbuild-essential-{arch}"));
+        cmd.arg(format!("libc6-{arch}-cross"));
+        cmd.arg(format!("libc6-dev-{arch}-cross"));
+        cmd.arg("dpkg-cross");
+        cmd.arg(format!("libc6:{arch}"));
+        cmd.arg(format!("libc6-dev:{arch}"));
+    }
+    let status = cmd.status()?;
+    if !status.success() {
+        return Err("Could not install essential packages for the build".into());
+    }
+
+    // Install build dependencies
+    log::debug!("Installing build dependencies...");
+    let mut cmd = ctx.command("apt-get");
+    cmd.current_dir(format!("{build_root}/{package}"))
+        .envs(env.clone())
+        .arg("-y")
+        .arg("build-dep");
+    if cross {
+        cmd.arg(format!("--host-architecture={arch}"));
+    }
+    let status = cmd.arg("./").status()?;
+
+    // If build-dep fails, we try to explain the failure using dose-debcheck
+    if !status.success() {
+        dose3_explain_dependencies(package, version, arch, build_root, cross)?;
+        return Err("Could not install build-dependencies for the build".into());
+    }
+
+    // Run the build step
+    log::debug!("Building (debian/rules build) package...");
+    let status = ctx
+        .command("debian/rules")
+        .current_dir(format!("{build_root}/{package}"))
+        .envs(env.clone())
+        .arg("build")
+        .status()?;
+    if !status.success() {
+        return Err("Error while building the package".into());
+    }
+
+    // Run the 'binary' step to produce deb
+    let status = ctx
+        .command("fakeroot")
+        .current_dir(format!("{build_root}/{package}"))
+        .envs(env.clone())
+        .arg("debian/rules")
+        .arg("binary")
+        .status()?;
+    if !status.success() {
+        return Err(
+            "Error while building the binary artifacts (.deb) from the built package".into(),
+        );
+    }
+
+    Ok(())
+}
+
+fn dose3_explain_dependencies(
+    package: &str,
+    version: &str,
+    arch: &str,
+    build_root: &str,
+    cross: bool,
+) -> Result<(), Box<dyn Error>> {
+    let ctx = context::current();
+
+    // Construct the list of Packages files
+    let mut bg_args = Vec::new();
+    let mut cmd = ctx.command("apt-get");
+    cmd.arg("indextargets")
+        .arg("--format")
+        .arg("$(FILENAME)")
+        .arg("Created-By: Packages");
+
+    let output = cmd.output()?;
+    if output.status.success() {
+        let filenames = String::from_utf8_lossy(&output.stdout);
+        for file in filenames.lines() {
+            let file = file.trim();
+            if !file.is_empty() {
+                bg_args.push(file.to_string());
+            }
+        }
+    }
+
+    // Transform the dsc file into a 'Source' stanza (replacing 'Source' with 'Package')
+    let dsc_path = find_dsc_file(build_root, package, version)?;
+    let mut dsc_content = ctx.read_file(&dsc_path)?;
+    dsc_content = dsc_content.replace("Source", "Package");
+    ctx.write_file(
+        Path::new(&format!("{build_root}/dsc-processed")),
+        &dsc_content,
+    )?;
+
+    // Call dose-builddebcheck
+    let local_arch = crate::get_current_arch();
+    let mut cmd = ctx.command("dose-builddebcheck");
+    cmd.arg("--verbose")
+        .arg("--failures")
+        .arg("--explain")
+        .arg("--summary")
+        .arg(format!("--deb-native-arch={}", local_arch));
+
+    if cross {
+        cmd.arg(format!("--deb-host-arch={}", arch))
+            .arg("--deb-profiles=cross")
+            .arg(format!("--deb-foreign-archs={}", arch));
+    }
+
+    cmd.args(bg_args).arg(format!("{build_root}/dsc-processed"));
+    cmd.status()?;
+    Ok(())
+}