Update FindFilesystem, re-enable support for CMake 3.10.

Also re-enable tests on Ubuntu bionic with GCC 7 and clang 6.

.drone.yml

@@ -78,35 +78,35 @@ steps:
   - name: debian-package-cache
     path: /var/cache/apt/archives
 
-# - name: GCC 7 / clang 6
-#   image: ubuntu:bionic
-#   pull: always
-#   environment:
-#     CXX: g++-7
-#     CXXFLAGS: -pipe -O2
-#     DEBIAN_FRONTEND: noninteractive
-#     LANG: C.utf8
-#     nlohmann_json_DIR: "/usr/lib/cmake"
-#   commands:
-#   - rm /etc/apt/apt.conf.d/docker-clean
-#   - alias apt-get='rm -f /var/cache/apt/archives/lock && apt-get'
-#   - apt-get update -q
-#   - apt-get install -qq build-essential cmake clang pkg-config
-#   - apt-get install -qq catch libcgicc-dev nlohmann-json-dev libgit2-dev libcurl4-openssl-dev
-#   - rm -rf build && mkdir -p build && cd build
-#   - cmake -G "Unix Makefiles" -DWITH_TESTS=YES ..
-#   - make VERBOSE=1
-#   - make install DESTDIR=install
-#   - cd tests && ctest -V
-#   - cd ../../
-#   - rm -rf build && mkdir -p build && cd build
-#   - CXX="clang++" cmake -G "Unix Makefiles" -DWITH_TESTS=YES ..
-#   - make VERBOSE=1
-#   - make install DESTDIR=install
-#   - cd tests && ctest -V
-#   volumes:
-#   - name: debian-package-cache
-#     path: /var/cache/apt/archives
+- name: GCC 7 / clang 6
+  image: ubuntu:bionic
+  pull: always
+  environment:
+    CXX: g++-7
+    CXXFLAGS: -pipe -O2
+    DEBIAN_FRONTEND: noninteractive
+    LANG: C.utf8
+    nlohmann_json_DIR: "/usr/lib/cmake"
+  commands:
+  - rm /etc/apt/apt.conf.d/docker-clean
+  - alias apt-get='rm -f /var/cache/apt/archives/lock && apt-get'
+  - apt-get update -q
+  - apt-get install -qq build-essential cmake clang pkg-config
+  - apt-get install -qq catch libcgicc-dev nlohmann-json-dev libgit2-dev libcurl4-openssl-dev
+  - rm -rf build && mkdir -p build && cd build
+  - cmake -G "Unix Makefiles" -DWITH_TESTS=YES ..
+  - make VERBOSE=1
+  - make install DESTDIR=install
+  - cd tests && ctest -V
+  - cd ../../
+  - rm -rf build && mkdir -p build && cd build
+  - CXX="clang++" cmake -G "Unix Makefiles" -DWITH_TESTS=YES ..
+  - make VERBOSE=1
+  - make install DESTDIR=install
+  - cd tests && ctest -V
+  volumes:
+  - name: debian-package-cache
+    path: /var/cache/apt/archives
 
 - name: notify
   image: drillster/drone-email

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.11...3.16)
+cmake_minimum_required(VERSION 3.10...3.16)
 # Ranges are supported from 3.12, set policy to current for < 3.12.
 if(${CMAKE_VERSION} VERSION_LESS 3.12)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})

README.adoc

@@ -68,12 +68,12 @@ Existing screenshots will not be overwritten.
 ==== Dependencies
 
 * Tested OS: Linux
-* C\++ compiler with C++17 support (tested: link:{uri-gcc}[GCC] 8/9/10,
-  link:{uri-clang}[clang] 7/10)
-* link:{uri-cmake}[CMake] (at least: 3.9)
+* C\++ compiler with C++17 support (tested: link:{uri-gcc}[GCC] 7/8/9/10,
+  link:{uri-clang}[clang] 6/7/10)
+* link:{uri-cmake}[CMake] (at least: 3.10)
 * link:{uri-cgicc}[cgicc] (tested: 3.2)
 * link:{uri-nlohmann-json}[nlohmann-json] (tested: 3.7 / 2.1)
-* link:{uri-libgit2}[libgit2] with SSH support (tested: 1.0 / 0.27)
+* link:{uri-libgit2}[libgit2] with SSH support (tested: 1.0 / 0.26)
 * link:{uri-libcurl}[libcurl] (at least: 7.56)
 * Optional
   ** Tests: link:{uri-catch}[Catch] (tested: 2.5 / 1.10)

cmake/FindFilesystem.cmake

@@ -102,6 +102,8 @@ if(TARGET std::filesystem)
     return()
 endif()
 
+cmake_minimum_required(VERSION 3.10)
+
 include(CMakePushCheckState)
 include(CheckIncludeFileCXX)
 include(CheckCXXSourceCompiles)
@@ -159,10 +161,12 @@ if(_CXX_FILESYSTEM_HAVE_HEADER)
     set(_have_fs TRUE)
     set(_fs_header filesystem)
     set(_fs_namespace std::filesystem)
+    set(_is_experimental FALSE)
 elseif(_CXX_FILESYSTEM_HAVE_EXPERIMENTAL_HEADER)
     set(_have_fs TRUE)
     set(_fs_header experimental/filesystem)
     set(_fs_namespace std::experimental::filesystem)
+    set(_is_experimental TRUE)
 else()
     set(_have_fs FALSE)
 endif()
@@ -170,6 +174,7 @@ endif()
 set(CXX_FILESYSTEM_HAVE_FS ${_have_fs} CACHE BOOL "TRUE if we have the C++ filesystem headers")
 set(CXX_FILESYSTEM_HEADER ${_fs_header} CACHE STRING "The header that should be included to obtain the filesystem APIs")
 set(CXX_FILESYSTEM_NAMESPACE ${_fs_namespace} CACHE STRING "The C++ namespace that contains the filesystem APIs")
+set(CXX_FILESYSTEM_IS_EXPERIMENTAL ${_is_experimental} CACHE BOOL "TRUE if the C++ filesystem library is the experimental version")
 
 set(_found FALSE)
 
@@ -205,15 +210,15 @@ if(CXX_FILESYSTEM_HAVE_FS)
 
     if(can_link)
         add_library(std::filesystem INTERFACE IMPORTED)
-        target_compile_features(std::filesystem INTERFACE cxx_std_17)
+        set_property(TARGET std::filesystem APPEND PROPERTY INTERFACE_COMPILE_FEATURES cxx_std_17)
         set(_found TRUE)
 
         if(CXX_FILESYSTEM_NO_LINK_NEEDED)
             # Nothing to add...
         elseif(CXX_FILESYSTEM_STDCPPFS_NEEDED)
-            target_link_libraries(std::filesystem INTERFACE -lstdc++fs)
+            set_property(TARGET std::filesystem APPEND PROPERTY INTERFACE_LINK_LIBRARIES -lstdc++fs)
         elseif(CXX_FILESYSTEM_CPPFS_NEEDED)
-            target_link_libraries(std::filesystem INTERFACE -lc++fs)
+            set_property(TARGET std::filesystem APPEND PROPERTY INTERFACE_LINK_LIBRARIES -lc++fs)
         endif()
     endif()
 endif()