build: Add git hash to version string

Embed git commit hash into version.h and irmd --version output using
git describe. Regenerated at build time to stay current across
commits.

Ouroboros version MAJOR.MINOR.PATCH (TAG-COMMITS-GHASH-dirty)

Example for dirty work tree (uncommitted changes):

  $ irmd --version
  Ouroboros version 0.22.0 (0.22.0-36-g86dba544-dirty)

Example after commit:

  $ sudo irmd --version
  Ouroboros version 0.22.0-37-g55fa9445

Officical release (on tag):
  Ouroboros version 0.22.0

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

4 files changed, 45 insertions, 3 deletions

diff --git a/cmake/include.cmake b/cmake/include.cmake
index ace51d0f..414ea0ad 100644
--- a/cmake/include.cmake
+++ b/cmake/include.cmake
@@ -2,9 +2,6 @@ set(HEADERS_SOURCE_DIR "${CMAKE_SOURCE_DIR}/include/ouroboros")
 
 # SOCK_BUF_SIZE is in cmake/config/global.cmake
 
-configure_file("${CMAKE_SOURCE_DIR}/include/ouroboros/version.h.in"
-  "${CMAKE_BINARY_DIR}/include/ouroboros/version.h" @ONLY)
-
 configure_file("${CMAKE_SOURCE_DIR}/include/ouroboros/sockets.h.in"
   "${CMAKE_BINARY_DIR}/include/ouroboros/sockets.h" @ONLY)
 
diff --git a/cmake/utils/GenVersionHeader.cmake b/cmake/utils/GenVersionHeader.cmake
new file mode 100644
index 00000000..5f5821b9
--- /dev/null
+++ b/cmake/utils/GenVersionHeader.cmake
@@ -0,0 +1,11 @@
+include(${CMAKE_CURRENT_LIST_DIR}/GetGitHash.cmake)
+get_git_hash(${GIT_DIR} ${PACKAGE_VERSION_MAJOR} ${PACKAGE_VERSION_MINOR} ${PACKAGE_VERSION_PATCH} PACKAGE_VERSION_STRING)
+
+configure_file(${INPUT_FILE} ${OUTPUT_FILE}.tmp @ONLY)
+
+execute_process(
+  COMMAND ${CMAKE_COMMAND} -E copy_if_different
+  ${OUTPUT_FILE}.tmp ${OUTPUT_FILE}
+)
+
+file(REMOVE ${OUTPUT_FILE}.tmp)
diff --git a/cmake/utils/GetGitHash.cmake b/cmake/utils/GetGitHash.cmake
new file mode 100644
index 00000000..8a9be41d
--- /dev/null
+++ b/cmake/utils/GetGitHash.cmake
@@ -0,0 +1,16 @@
+function(get_git_hash WORKING_DIR VERSION_MAJ VERSION_MIN VERSION_PAT OUTPUT_VAR)
+  execute_process(
+    COMMAND git describe --always --dirty
+    WORKING_DIRECTORY ${WORKING_DIR}
+    OUTPUT_VARIABLE _hash
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+    ERROR_QUIET
+  )
+
+  if(NOT _hash)
+    message(WARNING "Could not determine git hash")
+    set(_hash "${VERSION_MAJ}.${VERSION_MIN}.${VERSION_PAT}-custom")
+  endif()
+
+  set(${OUTPUT_VAR} "${_hash}" PARENT_SCOPE)
+endfunction()
diff --git a/cmake/version.cmake b/cmake/version.cmake
index 00183d34..1998e874 100644
--- a/cmake/version.cmake
+++ b/cmake/version.cmake
@@ -3,3 +3,21 @@ set(PACKAGE_VERSION_MINOR 22)
 set(PACKAGE_VERSION_PATCH  0)
 set(PACKAGE_VERSION
   "${PACKAGE_VERSION_MAJOR}.${PACKAGE_VERSION_MINOR}.${PACKAGE_VERSION_PATCH}")
+
+include(utils/GetGitHash)
+get_git_hash(${CMAKE_SOURCE_DIR} ${PACKAGE_VERSION_MAJOR} ${PACKAGE_VERSION_MINOR} ${PACKAGE_VERSION_PATCH} PACKAGE_VERSION_STRING)
+
+configure_file("${CMAKE_SOURCE_DIR}/include/ouroboros/version.h.in"
+  "${CMAKE_BINARY_DIR}/include/ouroboros/version.h" @ONLY)
+
+add_custom_target(version_header ALL
+  COMMAND ${CMAKE_COMMAND}
+    -DGIT_DIR=${CMAKE_SOURCE_DIR}
+    -DINPUT_FILE=${CMAKE_SOURCE_DIR}/include/ouroboros/version.h.in
+    -DOUTPUT_FILE=${CMAKE_BINARY_DIR}/include/ouroboros/version.h
+    -DPACKAGE_VERSION_MAJOR=${PACKAGE_VERSION_MAJOR}
+    -DPACKAGE_VERSION_MINOR=${PACKAGE_VERSION_MINOR}
+    -DPACKAGE_VERSION_PATCH=${PACKAGE_VERSION_PATCH}
+    -P ${CMAKE_SOURCE_DIR}/cmake/utils/GenVersionHeader.cmake
+  COMMENT "Updating git hash in version.h"
+)