new: template manifests and registry infrastructure

Split the Template trait into a data half and a logic half. Every
template is now declared by a manifest under data/templates/<id>/
(CLI id, wizard label, detection markers, Build-Depends, architecture,
rules dh line, rules-extra body, control source fields, gitignore
entries and static file bodies with {placeholder} substitution),
embedded through the TEMPLATE_SOURCES index and parsed once into the
registry; the order of the index is the wizard menu order and the
detection priority at once. The logic half is the slim TemplateHooks
trait (probe, post_write, file-body overrides merged over the manifest
bodies by path shadowing, Build-Depends/architecture amendments and
extra context values), registered per template as a HOOKS static: a
template without hooks needs zero Rust.

- TemplateId becomes a Copy wrapper of the stable CLI string; the
  enum, its all/as_str/display_name/from_label matches and the old
  statics array collapse into the registry accessors.
- rust's rules overrides move to data/templates/rust/rules.extra.tpl
  with {locked}/{artifact} hook context; python's backend table,
  meson/cmake's pkg-config opt-in, autotools' gettext and python's
  C-extension hints become hook amendments over the manifest baseline.
- detect.rs drops its hardcoded marker cascade: the manifests'
  detect.files drive detection in registry order, with the shell
  single-script heuristic and the never-detected empty template kept
  as the code special cases they are. License sniffing is untouched.
- The template tests port to manifest validation: registry coverage
  and stable order, placeholder presence in the rendering context,
  rules composition, the Build-Depends/architecture/dh-line table now
  asserted against the manifest data, and the hook shadowing merge.

The static skeleton bodies of the shell/empty/makefile/go templates
stay in their Rust hooks for now; the next commit moves them into
their manifests.

src/new/debian.rs

@@ -51,7 +51,7 @@ pub fn orig_tarball_path(
 }
 
 /// Render every common `debian/` file of the package.
-pub fn files(opts: &NewOptions, template: &dyn Template) -> Vec<OutputFile> {
+pub fn files(opts: &NewOptions, template: &Template) -> Vec<OutputFile> {
     let mut files = vec![
         source_format(opts),
         changelog(opts),
@@ -195,7 +195,7 @@ fn render_continuation_text(text: &str) -> String {
 /// comes from the template (`all` for shell/empty), and a non-empty
 /// `opts.depends` (the empty/metapackage flavor) lands in the binary
 /// stanza's `Depends` field.
-fn control(opts: &NewOptions, template: &dyn Template) -> OutputFile {
+fn control(opts: &NewOptions, template: &Template) -> OutputFile {
     let mut control = String::new();
 
     // Source stanza.
@@ -238,7 +238,7 @@ fn control(opts: &NewOptions, template: &dyn Template) -> OutputFile {
 /// `debian/rules`: the shebang and `%:` target whose recipe is the
 /// template's dh line (plus the template's extra overrides, when any),
 /// written with the executable bit.
-fn rules(opts: &NewOptions, template: &dyn Template) -> OutputFile {
+fn rules(opts: &NewOptions, template: &Template) -> OutputFile {
     let mut contents = format!("#!/usr/bin/make -f\n%:\n\t{}\n", template.rules_dh_line());
     let extra = template.rules_extra(opts);
     if !extra.is_empty() {
@@ -533,7 +533,7 @@ mod tests {
     fn opts() -> NewOptions {
         NewOptions {
             name: "mytool".into(),
-            template: TemplateId::Shell,
+            template: TemplateId::SHELL,
             source_dir: SourceDir::Skeleton,
             upstream_version: "0.1.0".into(),
             revision: 1,
@@ -559,7 +559,7 @@ mod tests {
     #[test]
     fn source_format_and_local_options() {
         let o = opts();
-        let files = super::files(&o, crate::new::templates::get(TemplateId::Shell).unwrap());
+        let files = super::files(&o, crate::new::templates::get(TemplateId::SHELL).unwrap());
         let find = |path: &str| {
             files
                 .iter()
@@ -582,7 +582,7 @@ mod tests {
         };
         let files = super::files(
             &native,
-            crate::new::templates::get(TemplateId::Shell).unwrap(),
+            crate::new::templates::get(TemplateId::SHELL).unwrap(),
         );
         assert!(
             files
@@ -642,7 +642,7 @@ mod tests {
     #[test]
     fn control_rendering_and_parse() {
         let o = opts();
-        let control = super::control(&o, crate::new::templates::get(TemplateId::Shell).unwrap());
+        let control = super::control(&o, crate::new::templates::get(TemplateId::SHELL).unwrap());
 
         // RFC822 continuation: first dep on the field line, the rest indented.
         assert!(
@@ -679,7 +679,7 @@ mod tests {
             homepage: None,
             ..opts()
         };
-        let control = super::control(&o, crate::new::templates::get(TemplateId::Shell).unwrap());
+        let control = super::control(&o, crate::new::templates::get(TemplateId::SHELL).unwrap());
         assert!(!control.contents.contains("Homepage:"));
         let parsed = crate::debian::ControlInfo::parse_content(&control.contents).unwrap();
         assert!(parsed.source.get("Homepage").is_none());
@@ -688,7 +688,7 @@ mod tests {
     #[test]
     fn rules_is_executable_minimal_makefile() {
         let o = opts();
-        let rules = super::rules(&o, crate::new::templates::get(TemplateId::Shell).unwrap());
+        let rules = super::rules(&o, crate::new::templates::get(TemplateId::SHELL).unwrap());
         assert!(rules.executable);
         assert_eq!(rules.contents, "#!/usr/bin/make -f\n%:\n\tdh $@\n");
     }
@@ -701,7 +701,7 @@ mod tests {
             "version=4\nhttps://github.com/example/mytool/releases .*/v?@ANY_VERSION@\\.tar\\.gz\n"
                 .to_string(),
         );
-        let files = super::files(&o, crate::new::templates::get(TemplateId::Shell).unwrap());
+        let files = super::files(&o, crate::new::templates::get(TemplateId::SHELL).unwrap());
         let find = |path: &str| {
             files
                 .iter()
@@ -731,7 +731,7 @@ mod tests {
         // Without the extras none of the files are rendered.
         let plain = super::files(
             &opts(),
-            crate::new::templates::get(TemplateId::Shell).unwrap(),
+            crate::new::templates::get(TemplateId::SHELL).unwrap(),
         );
         assert!(!plain.iter().any(|f| f.path.starts_with("debian/tests")));
         assert!(!plain.iter().any(|f| f.path == "debian/watch"));