feat(cmake): embed git info in binary (#644)

scripts/git.cmake

@@ -0,0 +1,35 @@
+find_package(Git)
+if(Git_FOUND)
+    message("Git found: ${GIT_EXECUTABLE}")
+
+    # the commit's SHA1, and whether the building workspace was dirty or not
+    execute_process(COMMAND
+        "${GIT_EXECUTABLE}" describe --match=NeVeRmAtCh --always --abbrev=40 --dirty
+        WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+        OUTPUT_VARIABLE GIT_SHA1
+        ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+    # the date of the commit
+    execute_process(COMMAND
+        "${GIT_EXECUTABLE}" log -1 --format=%ad --date=local
+        WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+        OUTPUT_VARIABLE GIT_DATE
+        ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+    # the subject of the commit
+    execute_process(COMMAND
+        "${GIT_EXECUTABLE}" log -1 --format=%s
+        WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+        OUTPUT_VARIABLE GIT_COMMIT_SUBJECT
+        ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+    # branch name
+    execute_process(COMMAND
+        "${GIT_EXECUTABLE}" branch --show-current
+        WORKING_DIRECTORY "${CMAKE_SOURCE_DIR}"
+        OUTPUT_VARIABLE GIT_BRANCH
+        ERROR_QUIET OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+    # generate version.cpp
+    configure_file("${SRC_DIR}/version.cpp.in" "${SRC_DIR}/version.cpp" @ONLY)
+endif()