Merge #16912: doc: Remove Doxygen intro from src/bitcoind.cpp

dbdc758c27cfdda9d255742b6c6ff4d1b7be82df doc: Improve doxygen readme navigation section (Jon Layton)
c15ac2c0aa45c59aee6d36c2d6d5210290dc601c doc: Move doxygen intro to file for USE_MDFILE_AS_MANPAGE (Jon Layton)

Pull request description:

  With `USE_MDFILE_AS_MAINPAGE`, this moves the introductory Doxygen comment to its own file. This makes `bitcoind.cpp` cleaner.

  It also removes the `\mainpage` header text, which was smaller than the section titles, and improves the Navigation section.

ACKs for top commit:
  promag:
    ACK dbdc758c27cfdda9d255742b6c6ff4d1b7be82df.

Tree-SHA512: 9352baad655877437913b74dc8888a71d1cccf55a837657ee2630fde3f427d0f0339155b7ab3d9e63a9edb9d53512d747eafcb11987a7c26c47a6df2eca93351

3 files changed, 17 insertions, 20 deletions

diff --git a/doc/Doxyfile.in b/doc/Doxyfile.in
index 399d54eb85..cd7ccf80ab 100644
--- a/doc/Doxyfile.in
+++ b/doc/Doxyfile.in
@@ -790,7 +790,7 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = src
+INPUT                  = src doc/README_doxygen.md
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses
@@ -974,7 +974,7 @@ FILTER_SOURCE_PATTERNS =
 # (index.html). This can be useful if you have a project on for instance GitHub
 # and want to reuse the introduction page also for the doxygen output.
 
-USE_MDFILE_AS_MAINPAGE =
+USE_MDFILE_AS_MAINPAGE = doc/README_doxygen.md
 
 #---------------------------------------------------------------------------
 # Configuration options related to source browsing
diff --git a/doc/README_doxygen.md b/doc/README_doxygen.md
new file mode 100644
index 0000000000..6888383a98
--- /dev/null
+++ b/doc/README_doxygen.md
@@ -0,0 +1,15 @@
+\mainpage notitle
+
+\section intro_sec Introduction
+
+This is the developer documentation of the reference client for an experimental new digital currency called Bitcoin,
+which enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate
+with no central authority: managing transactions and issuing money are carried out collectively by the network.
+
+The software is a community-driven open source project, released under the MIT license.
+
+See https://github.com/bitcoin/bitcoin and https://bitcoincore.org/ for further information about the project.
+
+\section Navigation
+Use <a href="modules.html"><code>Modules</code></a>, <a href="namespaces.html"><code>Namespaces</code></a>, <a href="classes.html"><code>Classes</code></a>, or <a href="files.html"><code>Files</code></a> at the top of the page to start navigating the code.
+
diff --git a/src/bitcoind.cpp b/src/bitcoind.cpp
index 83de684a2b..615b955f6e 100644
--- a/src/bitcoind.cpp
+++ b/src/bitcoind.cpp
@@ -25,24 +25,6 @@
 
 const std::function<std::string(const char*)> G_TRANSLATION_FUN = nullptr;
 
-/* Introduction text for doxygen: */
-
-/*! \mainpage Developer documentation
- *
- * \section intro_sec Introduction
- *
- * This is the developer documentation of the reference client for an experimental new digital currency called Bitcoin,
- * which enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate
- * with no central authority: managing transactions and issuing money are carried out collectively by the network.
- *
- * The software is a community-driven open source project, released under the MIT license.
- *
- * See https://github.com/bitcoin/bitcoin and https://bitcoincore.org/ for further information about the project.
- *
- * \section Navigation
- * Use the buttons <code>Namespaces</code>, <code>Classes</code> or <code>Files</code> at the top of the page to start navigating the code.
- */
-
 static void WaitForShutdown()
 {
     while (!ShutdownRequested())