meson: generate user manual

Our documentation contains a user manual that gives people a short
introduction to Git. Our Makefile knows to generate the manual into
three different formats: an HTML page, a PDF and an info page. The Meson
build instructions don't yet generate any of these.

While wiring up all these formats I hit a couple of road blocks with how
we generate our info pages. Even though I eventually resolved these, it
made me question whether anybody actually uses info pages in the first
place. Checking through a couple of downstream consumers I couldn't find
a single user of either the info pages nor of our PDF manual in Arch
Linux, Debian, Fedora, Ubuntu, FreeBSD or OpenBSDFedora. So it's rather
safe to assume that there aren't really any users out there, and thus
the added complexity does not seem worth it.

Wire up support for building the user manual in HTML format and
conciously skip over the other two formats. This is basically a form of
silent deprecation: if people out there use the other two formats they
will eventually complain about them missing in Meson, which means we can
wire them up at a later point. If they don't we can phase out these
formats eventually.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

Documentation/meson.build

@@ -382,3 +382,35 @@ foreach manpage, category : manpages
     )
   endif
 endforeach
+
+if get_option('docs').contains('html')
+  xsltproc = find_program('xsltproc')
+
+  user_manual_xml = custom_target(
+    command: asciidoc_common_options + [
+      '--backend=' + asciidoc_docbook,
+      '--doctype=book',
+      '--out-file=@OUTPUT@',
+      '@INPUT@',
+    ],
+    input: 'user-manual.txt',
+    output: 'user-manual.xml',
+    depends: documentation_deps,
+  )
+
+  custom_target(
+    command: [
+      xsltproc,
+      '--xinclude',
+      '--stringparam', 'html.stylesheet', 'docbook-xsl.css',
+      '--param', 'generate.consistent.ids', '1',
+      '--output', '@OUTPUT@',
+      '@INPUT@',
+      user_manual_xml,
+    ],
+    input: 'docbook.xsl',
+    output: 'user-manual.html',
+    install: true,
+    install_dir: get_option('datadir') / 'doc/git-doc',
+  )
+endif