title: How to avoid update checks with CMake FetchContent?
body: <p>all.</p>
  <p>I decided to use the new cmake macro to download external dependencies.
  I took the sample code from the documentation for the Catch2 library.</p>
  <pre><code>include(FetchContent)
  
  FetchContent_Declare(
      Catch2
      GIT_REPOSITORY https://github.com/catchorg/Catch2.git
      GIT_TAG        v2.13.4
  )
  FetchContent_GetProperties(Catch2)
  if(NOT Catch2_POPULATED)
      FetchContent_Populate(Catch2)
      add_subdirectory(${catch2_SOURCE_DIR} ${catch2_BINARY_DIR})
  endif()
  </code></pre>
  <p>The solution works great, except for the ability to restart the cmake when I am offline (no wifi and mobile network only me and my laptop).
  I get the following error:</p>
  <pre><code>[0/7] Performing update step for 'catch2-populate'
  fatal: «https://github.com/catchorg/Catch2.git/» недоступно: Could not resolve host: github.com
  CMake Error at /Users/evgeny.proydakov/repository/ihft/build/_deps/catch2-subbuild/catch2-populate-prefix/tmp/catch2-populate-gitupdate.cmake:97 (execute_process):
    execute_process failed command indexes:
  
      1: &quot;Child return code: 128&quot;
  
  FAILED: catch2-populate-prefix/src/catch2-populate-stamp/catch2-populate-update 
  cd /Users/evgeny.proydakov/repository/ihft/build/_deps/catch2-src &amp;&amp; /usr/local/Cellar/cmake/3.20.1/bin/cmake -P /Users/evgeny.proydakov/repository/ihft/build/_deps/catch2-subbuild/catch2-populate-prefix/tmp/catch2-populate-gitupdate.cmake
  ninja: build stopped: subcommand failed.
  
  CMake Error at /usr/local/Cellar/cmake/3.20.1/share/cmake/Modules/FetchContent.cmake:1012 (message):
    Build step for catch2 failed: 1
  Call Stack (most recent call first):
    /usr/local/Cellar/cmake/3.20.1/share/cmake/Modules/FetchContent.cmake:1141:EVAL:2 (__FetchContent_directPopulate)
    /usr/local/Cellar/cmake/3.20.1/share/cmake/Modules/FetchContent.cmake:1141 (cmake_language)
    /usr/local/Cellar/cmake/3.20.1/share/cmake/Modules/FetchContent.cmake:1184 (FetchContent_Populate)
    .cmake/icmake.cmake:46 (FetchContent_MakeAvailable)
    CMakeLists.txt:10 (include)
  
  -- Configuring incomplete, errors occurred!
  </code></pre>
  <p>Is it possible to download dependency one time, check revision and don't try to connect each time to remote server?</p>