cmake: refactor GitUtilities.cmake

Remote branch name can now be resolved from detached HEAD.

cmake/Modules/GitUtilities.cmake

@@ -6,54 +6,54 @@ endif()
 
 set(__GitUtilities ON)
 
-function(git_describe variable path)
-	execute_process(COMMAND "${GIT_EXECUTABLE}" "describe"
-		WORKING_DIRECTORY "${path}"
-		RESULT_VARIABLE result
+macro(_git_command)
+	execute_process(
+		COMMAND "${GIT_EXECUTABLE}" ${ARGN}
+		WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
 		OUTPUT_VARIABLE output
 		ERROR_QUIET
 		OUTPUT_STRIP_TRAILING_WHITESPACE
 	)
+endmacro()
 
+macro(_git_easy_command)
+	_git_command(${ARGN})
 	set(${variable} "${output}" PARENT_SCOPE)
-endfunction()
+endmacro()
 
-function(git_current_branch variable path)
-	execute_process(COMMAND ${GIT_EXECUTABLE} "symbolic-ref" "--short" "HEAD"
-		WORKING_DIRECTORY "${path}"
-		RESULT_VARIABLE result
-		OUTPUT_VARIABLE output
-		ERROR_QUIET
-		OUTPUT_STRIP_TRAILING_WHITESPACE
-	)
+function(git_current_branch variable)
+	_git_command(symbolic-ref -q --short HEAD)
 
-	set(${variable} "${output}" PARENT_SCOPE)
-endfunction()
+	# If a detached head, a ref could still be resolved.
+	if("${output}" STREQUAL "")
+		_git_command(describe --all --exact-match)
 
-function(git_latest_commit variable path)
-	execute_process(COMMAND ${GIT_EXECUTABLE} "rev-parse" "--short" "HEAD"
-		WORKING_DIRECTORY "${path}"
-		RESULT_VARIABLE result
-		OUTPUT_VARIABLE output
-		ERROR_QUIET
-		OUTPUT_STRIP_TRAILING_WHITESPACE
-	)
+		# Get the ref, in the form heads/master or
+		# remotes/origin/master so isolate the final part.
+		string(REGEX REPLACE ".*/" "" output "${output}")
+	endif()
 
 	set(${variable} "${output}" PARENT_SCOPE)
 endfunction()
 
-function(git_working_tree_dirty variable path)
-	execute_process(COMMAND ${GIT_EXECUTABLE} "status" "--porcelain" "-uno"
-		WORKING_DIRECTORY "${path}"
-		RESULT_VARIABLE result
-		OUTPUT_VARIABLE output
-		ERROR_QUIET
-		OUTPUT_STRIP_TRAILING_WHITESPACE
-	)
+function(git_latest_commit variable)
+	_git_easy_command(rev-parse --short HEAD)
+endfunction()
+
+function(git_working_tree_dirty variable)
+	_git_command(status --porcelain -uno)
 
 	if(output STREQUAL "")
 		set(${variable} FALSE PARENT_SCOPE)
 	else()
 		set(${variable} TRUE PARENT_SCOPE)
 	endif()
-endfunction()
\ No newline at end of file
+endfunction()
+
+function(git_summary variable)
+	_git_easy_command(log -1 "--format=%h %s")
+endfunction()
+
+function(get_git_dir variable)
+	_git_easy_command(rev-parse --git-dir)
+endfunction()