deb: build the tree the caller pointed at before the name search

build_binary_package stages the parent of the requested cwd, then
re-derived the package directory inside the staging area from
package/version name patterns plus the calling process's working
directory. That only works by accident for interactive users sitting
in the package directory: an embedded caller whose tree lives at
<job>/tree matches no pattern, and the process cwd means nothing to
a library consumer — the bc build above failed here even though the
tree was staged correctly.

The pointed-at tree is authoritative anyway: its changelog defined
the package, version and series for this build. Resolve its staged
copy outright when it carries a debian/ tree, keep the pattern
search (with the quirks overrides) as a fallback, and hand the
resolved directory to local::build instead of searching again.

src/deb/local.rs

@@ -34,6 +34,7 @@ pub async fn build(
     series: &str,
     pocket: Option<&str>,
     build_root: &str,
+    package_dir: &Path,
     cross: bool,
     ppa: &[String],
     inject_packages: &[String],
@@ -231,10 +232,8 @@ pub async fn build(
         return Err("Could not install essential packages for the build".into());
     }
 
-    // Find the actual package directory
+    // The package directory was resolved by the caller (the staged copy of
-    // Find the actual package directory
+    // the tree the user pointed at, or the name-pattern search fallback)
-    let package_dir =
-        crate::deb::find_package_directory(Path::new(build_root), package, version, series, &ctx)?;
     let package_dir_str = package_dir
         .to_str()
         .ok_or("Invalid package directory path")?;

src/deb/mod.rs

@@ -269,6 +269,19 @@ async fn build_binary_package_impl(
             .ok_or("Cannot find parent directory name")?;
         let build_root = format!("{}/{}", build_root, parent_dir_name.to_str().unwrap());
 
+        // Resolve the package directory inside the staging area. The tree
+        // the caller pointed at is authoritative (its changelog defined the
+        // package/version/series above), so its staged copy wins; the
+        // name-pattern search only runs as a fallback.
+        let package_dir = resolve_package_directory(
+            Path::new(&build_root),
+            cwd,
+            &package,
+            &version,
+            series,
+            &build_ctx,
+        )?;
+
         // Run the build using target build mode. It returns the exact set of
         // artifacts produced by this build (binary packages registered in
         // debian/files plus the generated .buildinfo/.changes), as paths
@@ -282,6 +295,7 @@ async fn build_binary_package_impl(
                     series,
                     pocket.as_deref(),
                     &build_root,
+                    &package_dir,
                     cross,
                     ppa,
                     inject,
@@ -329,6 +343,38 @@ async fn build_binary_package_impl(
     result
 }
 
+/// Resolve the package directory for a build inside the staged build root.
+///
+/// The tree the caller pointed at is authoritative: `cwd`'s changelog
+/// already defined the package, version and series for this build, so its
+/// staged copy is used outright when it carries a `debian/` tree. The
+/// name-pattern search ([`find_package_directory`], including the quirks
+/// overrides) only runs when that copy cannot be resolved — a default `.`
+/// cwd has no basename, and the pointed-at tree may live outside the staged
+/// parent. Embedded callers are the motivation: their working directory
+/// names (`tree`, `checkout`, ...) match none of the search patterns.
+pub(crate) fn resolve_package_directory(
+    build_root: &Path,
+    cwd: &Path,
+    package: &str,
+    version: &str,
+    series: &str,
+    ctx: &context::Context,
+) -> Result<PathBuf, Box<dyn Error>> {
+    if let Some(tree_name) = cwd.file_name() {
+        let staged_tree = build_root.join(tree_name);
+        if ctx.is_dir(&staged_tree)? && ctx.exists(&staged_tree.join("debian"))? {
+            log::debug!(
+                "Using the staged copy of {} at {}",
+                cwd.display(),
+                staged_tree.display()
+            );
+            return Ok(staged_tree);
+        }
+    }
+    find_package_directory(build_root, package, version, series, ctx)
+}
+
 /// Find the current package directory by trying both patterns:
 /// - package/package
 /// - package/package-origversion
@@ -548,6 +594,56 @@ mod tests {
         );
     }
 
+    /// An explicit cwd must resolve to its staged copy even when its name
+    /// matches none of the search patterns: the pointed-at tree is what the
+    /// parsed changelog came from.
+    #[test]
+    fn resolve_package_directory_prefers_the_pointed_tree() {
+        let chroot = tempfile::tempdir().unwrap();
+        let staged_parent = chroot.path().join("tmp/pkh-build-1/j-42");
+        std::fs::create_dir_all(staged_parent.join("tree/debian/source")).unwrap();
+
+        let ctx = unshare_test_context(chroot.path());
+        let resolved = resolve_package_directory(
+            Path::new("/tmp/pkh-build-1/j-42"),
+            Path::new("/work/jobs/j-42/tree"),
+            "bc",
+            "1.07.1-1ubuntu1",
+            "questing",
+            &ctx,
+        )
+        .expect("the staged copy of the pointed-at tree must resolve");
+
+        assert_eq!(resolved, PathBuf::from("/tmp/pkh-build-1/j-42/tree"));
+    }
+
+    /// When the pointed-at tree is not in the staging area under its own
+    /// name, resolution falls back to the name-pattern search.
+    #[test]
+    fn resolve_package_directory_falls_back_to_the_name_search() {
+        let chroot = tempfile::tempdir().unwrap();
+        let staged_parent = chroot.path().join("tmp/pkh-build-1/j-42");
+        // Staged copy of a pulled tree: <pkg>/<pkg>-<origversion>
+        std::fs::create_dir_all(staged_parent.join("bc/bc-1.07.1/debian")).unwrap();
+
+        let ctx = unshare_test_context(chroot.path());
+        let resolved = resolve_package_directory(
+            Path::new("/tmp/pkh-build-1/j-42"),
+            // A tree never staged under that name
+            Path::new("/work/other/checkout"),
+            "bc",
+            "1.07.1-1ubuntu1",
+            "questing",
+            &ctx,
+        )
+        .expect("the pulled-tree layout must resolve via the name search");
+
+        assert_eq!(
+            resolved,
+            PathBuf::from("/tmp/pkh-build-1/j-42/bc/bc-1.07.1")
+        );
+    }
+
     async fn test_build_end_to_end(
         package: &str,
         series: &str,
@@ -884,4 +980,80 @@ mod tests {
             "error should name the unsatisfied dependency: {err}"
         );
     }
+
+    /// An embedded-caller layout — the tree checked out at <job>/tree, a
+    /// name matching none of the search patterns — must build: the staged
+    /// copy of the tree the caller pointed at is resolved directly instead
+    /// of being re-derived from package/version names (which used to fail
+    /// with 'Could not find package directory').
+    #[tokio::test]
+    #[test_log::test]
+    async fn test_deb_builds_a_tree_named_directory_end_to_end() {
+        let temp_dir = tempfile::tempdir().unwrap();
+        let pkg_dir = temp_dir.path().join("j-42/tree");
+        std::fs::create_dir_all(pkg_dir.join("debian/source")).unwrap();
+
+        std::fs::write(
+            pkg_dir.join("debian/changelog"),
+            "pkh-treetest (1.0) noble; urgency=medium\n\n  \
+             * Synthetic package built from a directory named 'tree'.\n\n \
+             -- pkh tests <pkh@example.com>  Tue, 15 Sep 2026 08:00:00 +0000\n",
+        )
+        .unwrap();
+
+        std::fs::write(
+            pkg_dir.join("debian/control"),
+            "Source: pkh-treetest\n\
+             Section: devel\n\
+             Priority: optional\n\
+             Maintainer: pkh tests <pkh@example.com>\n\
+             Standards-Version: 4.7.4\n\
+             Build-Depends: debhelper-compat (= 13)\n\
+             Architecture: any\n\
+             \n\
+             Package: pkh-treetest\n\
+             Architecture: any\n\
+             Depends: ${misc:Depends}, ${shlibs:Depends}\n\
+             Description: Package-directory resolution regression package\n \
+              Its tree lives in a directory whose name matches none of the\n \
+              package-directory search patterns.\n",
+        )
+        .unwrap();
+
+        std::fs::write(
+            pkg_dir.join("debian/rules"),
+            "#!/usr/bin/make -f\n%:\n\tdh $@\n",
+        )
+        .unwrap();
+        use std::os::unix::fs::PermissionsExt;
+        let rules = pkg_dir.join("debian/rules");
+        let mut perms = std::fs::metadata(&rules).unwrap().permissions();
+        perms.set_mode(0o755);
+        std::fs::set_permissions(&rules, perms).unwrap();
+
+        std::fs::write(pkg_dir.join("debian/source/format"), "3.0 (native)\n").unwrap();
+
+        let ctx = Arc::new(Context::new(crate::context::ContextConfig::Local).unwrap());
+
+        crate::deb::build_binary_package(DebBuildOptions {
+            series: Some("noble".to_string()),
+            cwd: Some(pkg_dir),
+            ctx: Some(ctx),
+            ..Default::default()
+        })
+        .await
+        .expect("a tree named 'tree' must build");
+
+        let deb_files: Vec<String> = std::fs::read_dir(temp_dir.path().join("j-42"))
+            .unwrap()
+            .filter_map(|e| e.ok())
+            .map(|e| e.file_name().to_string_lossy().to_string())
+            .collect();
+        assert!(
+            deb_files
+                .iter()
+                .any(|f| f.starts_with("pkh-treetest_1.0_") && f.ends_with(".deb")),
+            ".deb not produced for the 'tree'-named directory, got: {deb_files:?}"
+        );
+    }
 }