[PATCH 01/10] meson: wire up support for AsciiDoctor

[Patrick Steinhardt <ps@xxxxxx>]

While our Makefile supports both Asciidoc and AsciiDoctor, our Meson
build instructions only support the former. Wire up support for the
latter, as well.

Our Makefile always favors Asciidoc, but Meson will automatically figure
out which of both to use based on whether they are installed or not. To
keep compatibility with our Makefile it favors Asciidoc over Asciidoctor
in case both are available.

Signed-off-by: Patrick Steinhardt <ps@xxxxxx>
---
 Documentation/meson.build | 107 ++++++++++++++++++++++++++++++++++------------
 meson_options.txt         |   2 +
 2 files changed, 82 insertions(+), 27 deletions(-)

diff --git a/Documentation/meson.build b/Documentation/meson.build
index f2426ccaa30c29bd60b850eb0a9a4ab77c66a629..d62b0846d3f8ebc412f5fa9f775f037a3656093a 100644
--- a/Documentation/meson.build
+++ b/Documentation/meson.build
@@ -204,28 +204,85 @@ manpages = {
   'gitworkflows.txt' : 7,
 }
 
-asciidoc = find_program('asciidoc')
-git = find_program('git', required: false)
-xmlto = find_program('xmlto')
+docs_backend = get_option('docs_backend')
+if docs_backend == 'auto'
+  if find_program('asciidoc', required: false).found()
+    docs_backend = 'asciidoc'
+  elif find_program('asciidoctor', required: false).found()
+    docs_backend = 'asciidoctor'
+  else
+    error('Neither asciidoc nor asciidoctor were found.')
+  endif
+endif
 
-asciidoc_conf = custom_target(
-  command: [
-    shell,
-    meson.project_source_root() / 'GIT-VERSION-GEN',
-    meson.project_source_root(),
-    '@INPUT@',
-    '@OUTPUT@',
-  ],
-  input: meson.current_source_dir() / 'asciidoc.conf.in',
-  output: 'asciidoc.conf',
-  depends: [git_version_file],
-)
+if docs_backend == 'asciidoc'
+  asciidoc = find_program('asciidoc', required: true)
+  asciidoc_html = 'xhtml11'
+  asciidoc_docbook = 'docbook'
+  xmlto_extra = [ ]
 
-asciidoc_common_options = [
-  asciidoc,
-  '--conf-file=' + asciidoc_conf.full_path(),
-  '--attribute=build_dir=' + meson.current_build_dir(),
-]
+  asciidoc_conf = custom_target(
+    command: [
+      shell,
+      meson.project_source_root() / 'GIT-VERSION-GEN',
+      meson.project_source_root(),
+      '@INPUT@',
+      '@OUTPUT@',
+    ],
+    input: meson.current_source_dir() / 'asciidoc.conf.in',
+    output: 'asciidoc.conf',
+    depends: [git_version_file],
+  )
+
+  asciidoc_common_options = [
+    asciidoc,
+    '--conf-file=' + asciidoc_conf.full_path(),
+    '--attribute=build_dir=' + meson.current_build_dir(),
+  ]
+
+  documentation_deps = [
+    asciidoc_conf,
+  ]
+elif docs_backend == 'asciidoctor'
+  asciidoctor = find_program('asciidoctor', required: true)
+  asciidoc_html = 'xhtml5'
+  asciidoc_docbook = 'docbook5'
+  xmlto_extra = [
+    '--skip-validation',
+    '-x', meson.current_source_dir() / 'manpage.xsl',
+  ]
+
+  asciidoctor_extensions = custom_target(
+    command: [
+      shell,
+      meson.project_source_root() / 'GIT-VERSION-GEN',
+      meson.project_source_root(),
+      '@INPUT@',
+      '@OUTPUT@',
+    ],
+    input: meson.current_source_dir() / 'asciidoctor-extensions.rb.in',
+    output: 'asciidoctor-extensions.rb',
+    depends: [git_version_file],
+  )
+
+  asciidoc_common_options = [
+    asciidoctor,
+    '--attribute', 'compat-mode',
+    '--attribute', 'tabsize=8',
+    '--attribute', 'litdd=&#x2d;&#x2d;',
+    '--attribute', 'docinfo=shared',
+    '--attribute', 'build_dir=' + meson.current_build_dir(),
+    '--load-path', meson.current_build_dir(),
+    '--require', 'asciidoctor-extensions',
+  ]
+
+  documentation_deps = [
+    asciidoctor_extensions,
+  ]
+endif
+
+git = find_program('git', required: false)
+xmlto = find_program('xmlto')
 
 cmd_lists = [
   'cmds-ancillaryinterrogators.txt',
@@ -242,10 +299,6 @@ cmd_lists = [
   'cmds-foreignscminterface.txt',
 ]
 
-documentation_deps = [
-  asciidoc_conf,
-]
-
 documentation_deps += custom_target(
   command: [
     perl,
@@ -277,7 +330,7 @@ foreach manpage, category : manpages
   if get_option('docs').contains('man')
     manpage_xml_target = custom_target(
       command: asciidoc_common_options + [
-        '--backend=docbook',
+        '--backend=' + asciidoc_docbook,
         '--doctype=manpage',
         '--out-file=@OUTPUT@',
         meson.current_source_dir() / manpage,
@@ -300,7 +353,7 @@ foreach manpage, category : manpages
         manpage_xml_target,
         '-o',
         meson.current_build_dir(),
-      ],
+      ] + xmlto_extra,
       output: manpage_path,
       install: true,
       install_dir: get_option('mandir') / 'man' + category.to_string(),
@@ -310,7 +363,7 @@ foreach manpage, category : manpages
   if get_option('docs').contains('html') and category == 1
     custom_target(
       command: asciidoc_common_options + [
-        '--backend=xhtml11',
+        '--backend=' + asciidoc_html,
         '--doctype=manpage',
         '--out-file=@OUTPUT@',
         meson.current_source_dir() / manpage,
diff --git a/meson_options.txt b/meson_options.txt
index 32a72139bae870745d9131cc9086a4594826be91..0d8ba28de6da7d0ed2ac4bdef7efa967509ec898 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -73,6 +73,8 @@ option('docs', type: 'array', choices: ['man', 'html'], value: [],
   description: 'Which documenattion formats to build and install.')
 option('default_help_format', type: 'combo', choices: ['man', 'html'], value: 'man',
   description: 'Default format used when executing git-help(1).')
+option('docs_backend', type: 'combo', choices: ['asciidoc', 'asciidoctor', 'auto'], value: 'auto',
+  description: 'Which backend to use to generate documentation.')
 
 # Testing.
 option('tests', type: 'boolean', value: true,

-- 
2.47.1.668.gf74b3f243a.dirty