Fix/revisit git-describe enhancement (#11124)

* Fix/keep massaging git-describe result

Ref: https://github.com/neovim/neovim/pull/11117#issuecomment-536416223

* build: revisit generation of version from Git

Fixes "make clean && make", where "auto/versiondef.h" would be missing
since b18b84d - because BYPRODUCTS are apparently removed when cleaning.

This includes the following improvements/changes:

- do not run git-describe during CMake's configure phase just for
  reporting
- do not print with changed Git version (too noisy, simplifies code)

* Move to src/nvim (included before config) for easier flow

* fallback to describe always, write empty include file

* update_version_stamp.lua: use prefix always

config/CMakeLists.txt

@@ -121,35 +121,6 @@ configure_file (
   )
 
 # generate version definitions
-if(NVIM_VERSION_MEDIUM)
-  message(STATUS "NVIM_VERSION_MEDIUM: ${NVIM_VERSION_MEDIUM}")
-elseif(${CMAKE_VERSION} VERSION_LESS "3.2.0")
-  message(STATUS "Skipping version-string generation (requires CMake 3.2.0+)")
-elseif(EXISTS ${PROJECT_SOURCE_DIR}/.git)
-  find_program(GIT_EXECUTABLE git)
-  if(GIT_EXECUTABLE)
-    # Get current version.
-    execute_process(
-      COMMAND ${GIT_EXECUTABLE} describe --dirty
-      WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
-      OUTPUT_VARIABLE NVIM_VERSION_MEDIUM
-      OUTPUT_STRIP_TRAILING_WHITESPACE)
-    message(STATUS "NVIM_VERSION_MEDIUM (from git): ${NVIM_VERSION_MEDIUM}")
-
-    # Create a update_version_stamp target to update the version during build.
-    file(RELATIVE_PATH relbuild "${PROJECT_SOURCE_DIR}" "${CMAKE_BINARY_DIR}")
-    add_custom_target(update_version_stamp ALL
-      COMMAND ${LUA_PRG} scripts/update_version_stamp.lua
-        ${relbuild}/.version_stamp
-        ${relbuild}/config/auto/versiondef.h
-      WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
-      BYPRODUCTS ${CMAKE_BINARY_DIR}/config/auto/versiondef.h)
-    add_dependencies(nvim update_version_stamp)
-  else()
-  message(STATUS "Skipping version-string generation (cannot find git)")
-  endif()
-endif()
-
 configure_file (
   "${PROJECT_SOURCE_DIR}/config/versiondef.h.in"
   "${PROJECT_BINARY_DIR}/config/auto/versiondef.h"

config/versiondef.h.in

@@ -5,7 +5,11 @@
 #define NVIM_VERSION_MINOR @NVIM_VERSION_MINOR@
 #define NVIM_VERSION_PATCH @NVIM_VERSION_PATCH@
 #define NVIM_VERSION_PRERELEASE "@NVIM_VERSION_PRERELEASE@"
+
 #cmakedefine NVIM_VERSION_MEDIUM "@NVIM_VERSION_MEDIUM@"
+#ifndef NVIM_VERSION_MEDIUM
+# include "auto/versiondef_git.h"
+#endif
 
 #define NVIM_API_LEVEL @NVIM_API_LEVEL@
 #define NVIM_API_LEVEL_COMPAT @NVIM_API_LEVEL_COMPAT@

scripts/update_version_stamp.lua

@@ -4,11 +4,11 @@
 -- This is called via the custom update_version_stamp target in
 -- src/nvim/CMakeLists.txt.
 --
--- arg[1]: file containing the last git-describe output
--- arg[2]: file in which to update the version string
+-- arg[1]: file in which to update the version string
+-- arg[2]: prefix to use always ("vX.Y.Z")
 
 local function die(msg)
-  print(string.format('%s: %s', arg[0], msg))
+  io.stderr:write(string.format('%s: %s\n', arg[0], msg))
   -- No error, fall back to using generated "-dev" version.
   os.exit(0)
 end
@@ -17,29 +17,34 @@ if #arg ~= 2 then
   die(string.format("Expected two args, got %d", #arg))
 end
 
-local stampfile = arg[1]
-local stamp = io.open(stampfile, 'r')
-if stamp then
-  stamp = stamp:read('*l')
+local versiondeffile = arg[1]
+local prefix = arg[2]
+
+local described = io.popen('git describe --dirty'):read('*l')
+if not described then
+  described = io.popen('git describe --tags --always --dirty'):read('*l')
+end
+if not described then
+  io.open(versiondeffile, 'w'):write('\n')
+  die('git-describe failed, using empty include file.')
 end
 
-local current = io.popen('git describe --dirty'):read('*l')
-if not current then
-  die('git-describe failed')
+-- `git describe` annotates the most recent tagged release; for pre-release
+-- builds we must replace that with the unreleased version.
+local with_prefix = described:gsub("^v%d+%.%d+%.%d+", prefix)
+if described == with_prefix then
+  -- Prepend the prefix always, e.g. with "nightly-12208-g4041b62b9".
+  with_prefix = prefix .. "-" .. described
 end
 
-if stamp ~= current then
-  if stamp then
-    print(string.format('git version changed: %s -> %s', stamp, current))
-  end
-  local new_lines = {}
-  local versiondeffile = arg[2]
-  for line in io.lines(versiondeffile) do
-    if line:match("NVIM_VERSION_MEDIUM") then
-      line = '#define NVIM_VERSION_MEDIUM "'..current..'"'
-    end
-    new_lines[#new_lines + 1] = line
-  end
-  io.open(versiondeffile, 'w'):write(table.concat(new_lines, '\n') .. '\n')
-  io.open(stampfile, 'w'):write(current)
+-- Read existing include file.
+local current = io.open(versiondeffile, 'r')
+if current then
+  current = current:read('*l')
+end
+
+-- Write new include file, if different.
+local new = '#define NVIM_VERSION_MEDIUM "'..with_prefix..'"'
+if current ~= new then
+  io.open(versiondeffile, 'w'):write(new .. '\n')
 end

src/nvim/CMakeLists.txt

@@ -217,6 +217,34 @@ function(get_preproc_output varname iname)
   endif()
 endfunction()
 
+# Handle generating version from Git.
+set(use_git_version 0)
+if(NVIM_VERSION_MEDIUM)
+  message(STATUS "NVIM_VERSION_MEDIUM: ${NVIM_VERSION_MEDIUM}")
+elseif(${CMAKE_VERSION} VERSION_LESS "3.2.0")
+  message(STATUS "Skipping version-string generation (requires CMake 3.2.0+)")
+elseif(EXISTS ${PROJECT_SOURCE_DIR}/.git)
+  find_program(GIT_EXECUTABLE git)
+  if(GIT_EXECUTABLE)
+    message(STATUS "Using NVIM_VERSION_MEDIUM from Git")
+    set(use_git_version 1)
+  else()
+    message(STATUS "Skipping version-string generation (cannot find git)")
+  endif()
+endif()
+if(use_git_version)
+  # Create a update_version_stamp target to update the version during build.
+  file(RELATIVE_PATH relbuild "${PROJECT_SOURCE_DIR}" "${CMAKE_BINARY_DIR}")
+  add_custom_target(update_version_stamp ALL
+    COMMAND ${LUA_PRG} scripts/update_version_stamp.lua
+      ${relbuild}/config/auto/versiondef_git.h
+      "v${NVIM_VERSION_MAJOR}.${NVIM_VERSION_MINOR}.${NVIM_VERSION_PATCH}"
+    WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
+    BYPRODUCTS ${CMAKE_BINARY_DIR}/config/auto/versiondef_git.h)
+else()
+  file(WRITE ${CMAKE_BINARY_DIR}/config/auto/versiondef_git.h "")
+endif()
+
 # NVIM_GENERATED_FOR_HEADERS: generated headers to be included in headers
 # NVIM_GENERATED_FOR_SOURCES: generated headers to be included in sources
 # NVIM_GENERATED_SOURCES: generated source files
@@ -245,12 +273,16 @@ foreach(sfile ${NVIM_SOURCES}
 
   get_preproc_output(PREPROC_OUTPUT ${gf_i})
 
+  set(depends "${HEADER_GENERATOR}" "${sfile}")
+  if(use_git_version AND "${f}" STREQUAL "version.c")
+    # Ensure auto/versiondef_git.h exists after "make clean".
+    list(APPEND depends update_version_stamp)
+  endif()
   add_custom_command(
     OUTPUT "${gf_c_h}" "${gf_h_h}"
     COMMAND ${CMAKE_C_COMPILER} ${sfile} ${PREPROC_OUTPUT} ${gen_cflags} ${C_FLAGS_ARRAY}
     COMMAND "${LUA_PRG}" "${HEADER_GENERATOR}" "${sfile}" "${gf_c_h}" "${gf_h_h}" "${gf_i}"
-    DEPENDS "${HEADER_GENERATOR}" "${sfile}"
-    )
+    DEPENDS ${depends})
   list(APPEND NVIM_GENERATED_FOR_SOURCES "${gf_c_h}")
   list(APPEND NVIM_GENERATED_FOR_HEADERS "${gf_h_h}")
   if(${d} MATCHES "^api$" AND NOT ${f} MATCHES "^api/helpers.c$")