pod: generate the po4a configuration, --po4a-cfg

A document's po4a configuration is derived rather than kept. Spine
already knows both halves without looking: the manifest says which
languages, and the markup says which files, through the << lines the
parser follows. Derived, it cannot disagree with the document, where a
hand-kept file eventually does: a language added to the manifest and
forgotten in the Makefile is a translation nobody updates.

It prints, rather than writing. Spine does not write into a source tree,
and the file belongs beside the catalogues in the pod it describes:

  spine --po4a-cfg <pod> > <pod>/tools/po4a/po4a.cfg

Three things the Makefile it replaces knew, which had to be found by
running po4a rather than by reading:

--keep 0 is the difference between regenerating a document and
destroying it. po4a will not write a translated file below a
completeness threshold, and that threshold defaults to 80%. A partly
translated document is the normal state of one being worked on, and sisu
covers it: an untranslated string falls back to the source text.
Measured at the default, 181 of live-manual's 189 translated files would
be discarded, and nine languages would collapse to eight surviving
files, reading as the document reverting to its source language rather
than as a failure.

index.html.in is not markup and no << line names it, so a configuration
built from the manifest and the insert list alone drops it, and with it
index.html.in.pot and its nine .po files at the next regeneration. It is
found by asking whether the source language has one.

neverwrap is not set, and the measurement is recorded beside the code:
setting it turns 889 of 1126 strings fuzzy in four languages, and po4a
does not use a fuzzy translation, so Catalan's coverage would fall from
about 46% to about 12%. Tidy formatting is not worth that.

The run-complete banner is suppressed for this action. The configuration
goes to stdout and the banner would otherwise be part of the file, which
is what the round trips already avoid by leaving early; this one prints
from inside output processing and cannot.

(assisted by Claude-Code)

1 files changed, 15 insertions, 0 deletions

diff --git a/src/sisudoc/outputs/io_out/hub.d b/src/sisudoc/outputs/io_out/hub.d
index 0973097..254eaa5 100644
--- a/src/sisudoc/outputs/io_out/hub.d
+++ b/src/sisudoc/outputs/io_out/hub.d
@@ -62,6 +62,21 @@ template outputHub() {
   @system void outputHub(D)(D doc) {
     mixin Msg;
     auto msg = Msg!()(doc.matters);
+    /+ ↓ the po4a configuration, printed rather than written.
+         Spine does not write into a source tree, and this belongs beside the
+         catalogues in the pod it describes, so it goes to stdout for the
+         caller to put where they want it:
+           spine --po4a-cfg <pod> > <pod>/tools/po4a/po4a.cfg
+         Once per document, not once per language: it is generated from the
+         source language's files and names every other language itself.
+    +/
+    if (doc.matters.opt.action.po4a_cfg
+      && doc.matters.src.language == doc.matters.pod.manifest_list_of_languages[0]
+    ) {
+      import sisudoc.outputs.io_out.po4a_cfg;
+      mixin spinePo4aConfig;
+      write(po4aConfig(doc.matters));
+    }
     enum outTask { source_or_pod, sqlite, sqlite_multi, latex, odt, epub, html_scroll, html_seg, html_stuff, text, skel }
     void Scheduled(D)(int sched, D doc) {
       auto msg = Msg!()(doc.matters);