build: factor out manpage generation from toplevel CMakeLists.txt

CMakeLists.txt

@@ -228,41 +228,9 @@ if(STATIC_BUILD_DO_NOT_USE)
 endif()
 
 if(WITH_MAN_PAGES)
-  if(DWARFS_GIT_BUILD)
-    find_program(RONN_EXE ronn DOC "ronn man page generator" REQUIRED)
-  endif()
-
+  include("${CMAKE_SOURCE_DIR}/cmake/manpage.cmake")
   foreach(man dwarfs.1 mkdwarfs.1 dwarfsck.1 dwarfsextract.1 dwarfs-format.5)
-    string(REGEX MATCH "^[^.]*" docname "${man}")
-    string(REGEX MATCH "[^.]*$" section "${man}")
-
-    if(DWARFS_GIT_BUILD)
-      set(man_dir "${CMAKE_CURRENT_BINARY_DIR}/man${section}")
-      set(man_input "${CMAKE_CURRENT_SOURCE_DIR}/doc/${docname}.md")
-      set(man_output "${man_dir}/${man}")
-
-      execute_process(
-        COMMAND ${RONN_EXE}
-        INPUT_FILE "${man_input}"
-        RESULT_VARIABLE ronn_result
-        OUTPUT_VARIABLE ronn_output
-        ERROR_VARIABLE ronn_error)
-
-      if(${ronn_result} EQUAL 0)
-        add_custom_command(
-          OUTPUT "${man_output}"
-          COMMAND mkdir -p "${man_dir}"
-          COMMAND ${RONN_EXE} <"${man_input}" >"${man_output}"
-          DEPENDS "${man_input}")
-        list(APPEND MAN_PAGES "${man_output}")
-        list(APPEND MAN_DIRS "${man_dir}")
-      else()
-        message(WARNING "${RONN_EXE} failed to process ${man_input} -> ${man}")
-        message(WARNING "error: ${ronn_error}")
-      endif()
-    else()
-      list(APPEND MAN_DIRS "${CMAKE_CURRENT_SOURCE_DIR}/doc/man${section}")
-    endif()
+    add_manpage(${man})
   endforeach()
 endif()
 
@@ -851,13 +819,6 @@ if(WITH_FUZZ)
   list(APPEND BINARY_TARGETS fuzz_mkdwarfs)
 endif()
 
-if(WITH_MAN_PAGES)
-  list(REMOVE_DUPLICATES MAN_DIRS)
-  if(DWARFS_GIT_BUILD)
-    add_custom_target(manpages ALL DEPENDS ${MAN_PAGES})
-  endif()
-endif()
-
 target_link_libraries(dwarfs_common PRIVATE dwarfs_thrift_lite)
 
 add_cpp2_thrift_library(fbthrift/thrift/lib/thrift/frozen.thrift
@@ -1184,10 +1145,6 @@ add_custom_target(
   format
   COMMAND clang-format -i ${ALL_SOURCES})
 
-foreach(man_dir ${MAN_DIRS})
-  install(DIRECTORY "${man_dir}" DESTINATION share/man)
-endforeach()
-
 if(NOT STATIC_BUILD_DO_NOT_USE)
   foreach(tgt dwarfs_common dwarfs_reader dwarfs_writer dwarfs_extractor dwarfs_rewrite)
     set_target_properties(${tgt} PROPERTIES VERSION ${PRJ_VERSION_MAJOR}.${PRJ_VERSION_MINOR}.${PRJ_VERSION_PATCH})

cmake/manpage.cmake

@@ -0,0 +1,73 @@
+#
+# Copyright (c) Marcus Holland-Moritz
+#
+# This file is part of dwarfs.
+#
+# dwarfs is free software: you can redistribute it and/or modify it under the
+# terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+#
+# dwarfs is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# dwarfs.  If not, see <https://www.gnu.org/licenses/>.
+#
+
+cmake_minimum_required(VERSION 3.28.0)
+
+function(add_manpage MANPAGE)
+  if(DWARFS_GIT_BUILD)
+    find_program(RONN_EXE ronn DOC "ronn man page generator" REQUIRED)
+  endif()
+
+  if(NOT TARGET manpages)
+    add_custom_target(manpages ALL)
+    set_target_properties(manpages PROPERTIES MANPAGE_DIRECTORIES "")
+  endif()
+
+  string(REGEX MATCH "^[^.]*" _docname "${MANPAGE}")
+  string(REGEX MATCH "[^.]*$" _section "${MANPAGE}")
+
+  set(_man_dir "")
+
+  if(DWARFS_GIT_BUILD)
+    set(_man_input "${CMAKE_CURRENT_SOURCE_DIR}/doc/${_docname}.md")
+
+    execute_process(
+      COMMAND ${RONN_EXE}
+      INPUT_FILE "${_man_input}"
+      RESULT_VARIABLE _ronn_result
+      OUTPUT_VARIABLE _ronn_output
+      ERROR_VARIABLE _ronn_error)
+
+    if(${_ronn_result} EQUAL 0)
+      set(_man_dir "${CMAKE_CURRENT_BINARY_DIR}/man${_section}")
+      set(_man_output "${_man_dir}/${MANPAGE}")
+      add_custom_command(
+        OUTPUT "${_man_output}"
+        COMMAND ${CMAKE_COMMAND} -E make_directory "${_man_dir}"
+        COMMAND ${RONN_EXE} <"${_man_input}" >"${_man_output}"
+        DEPENDS "${_man_input}")
+      add_custom_target("_manpage_${_docname}_${_section}" DEPENDS "${_man_output}")
+      add_dependencies(manpages "_manpage_${_docname}_${_section}")
+    else()
+      message(WARNING "${RONN_EXE} failed to process ${_man_input} -> ${MANPAGE}")
+      message(WARNING "error: ${_ronn_error}")
+    endif()
+  else()
+    set(_man_dir "${CMAKE_CURRENT_SOURCE_DIR}/doc/man${_section}")
+  endif()
+
+  if(_man_dir)
+    get_target_property(_man_dirs manpages MANPAGE_DIRECTORIES)
+    list(FIND _man_dirs "${_man_dir}" _index)
+    if(${_index} EQUAL -1)
+      list(APPEND _man_dirs "${_man_dir}")
+      install(DIRECTORY "${_man_dir}" DESTINATION share/man)
+      set_target_properties(manpages PROPERTIES MANPAGE_DIRECTORIES "${_man_dirs}")
+    endif()
+  endif()
+endfunction()