Block in-source builds and add clean_all target

Summary:
Add detecting and blocking in-source builds

A simple cmake function, which detects if the source and build dir are
one and the same. This unfortunately does not catch the case when the
build dir is inside the source dir, since we actually want to support
that. For example, creating a 'build' directory inside the project
source directory should be allowed.

Add a clean_all custom target in cmake

This target will clean all the files inside the build directory. It
should be used with care!

A new cmake module is created, since invoking cmake -E remove_directory
will delete the directory and we want to keep it. This way, we also
avoid using platform specific shell command, i.e `rm -rf` and we can
make clean_all smarter in the future.

Untrack build/.gitignore from git

Reviewers: buda

Reviewed By: buda

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D92

.gitignore

@@ -20,7 +20,7 @@ release/memgraph_*
 release/libs/
 release/barrier/
 release/barrier_*
-build/compiled/
+build/
 cmake-build-*
 .idea
 cmake/DownloadProject/

CMakeLists.txt

@@ -40,6 +40,13 @@ set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${PROJECT_SOURCE_DIR}/cmake)
 include(functions)
 # -----------------------------------------------------------------------------
 
+# We want out of source builds, so that cmake generated files don't get mixed
+# with source files. This allows for easier clean up.
+disallow_in_source_build()
+add_custom_target(clean_all
+                  COMMAND ${CMAKE_COMMAND} -P ${PROJECT_SOURCE_DIR}/cmake/clean_all.cmake
+                  COMMENT "Removing all files in ${CMAKE_BINARY_DIR}")
+
 # threading
 find_package(Threads REQUIRED)
 # -----------------------------------------------------------------------------

build/.gitignore

@@ -1,2 +0,0 @@
-/*
-!.gitignore

cmake/clean_all.cmake

@@ -0,0 +1,2 @@
+file(GLOB build_contents "${CMAKE_BINARY_DIR}/*")
+file(REMOVE_RECURSE ${build_contents})

cmake/functions.cmake

@@ -27,3 +27,19 @@ MACRO(SUBDIRLIST result curdir)
     ENDFOREACH()
     SET(${result} ${dirlist})
 ENDMACRO()
+
+function(disallow_in_source_build)
+    get_filename_component(src_dir ${CMAKE_SOURCE_DIR} REALPATH)
+    get_filename_component(bin_dir ${CMAKE_BINARY_DIR} REALPATH)
+    message(STATUS "SOURCE_DIR" ${src_dir})
+    message(STATUS "BINARY_DIR" ${bin_dir})
+    # Do we maybe want to limit out-of-source builds to be only inside a
+    # directory which contains 'build' in name?
+    if("${src_dir}" STREQUAL "${bin_dir}")
+        # Unfortunately, we cannot remove CMakeCache.txt and CMakeFiles here
+        # because they are written after cmake is done.
+        message(FATAL_ERROR "In source build is not supported! "
+                "Remove CMakeCache.txt and CMakeFiles and then create a separate "
+                "directory, e.g. 'build' and run cmake there.")
+    endif()
+endfunction()

init.sh

@@ -5,6 +5,9 @@ for pkg in wget git cmake uuid-dev clang-3.8; do
     dpkg -s $pkg 2>/dev/null >/dev/null || sudo apt-get -y install $pkg
 done
 
+# create a default build directory
+mkdir -p ./build
+
 # setup libs (download)
 cd libs
 ./setup.sh