ExternalProject: retry download on recoverable errors

In order to shorten the download failure of ExternalProject download
steps, a download retry is only done when a recoverable network
error is encountered.

Modules/ExternalProject-download.cmake.in

@@ -107,11 +107,15 @@ message(STATUS "Downloading...
    dst='@LOCAL@'
    timeout='@TIMEOUT_MSG@'"
 )
-
+set(download_retry_codes 7 6 8 15)
+set(skip_url_list)
+set(status_code)
 foreach(i RANGE ${retry_number})
+  if(status_code IN_LIST download_retry_codes)
     sleep_before_download(${i})
-
+  endif()
   foreach(url @REMOTE@)
+    if(NOT url IN_LIST skip_url_list)
       message(STATUS "Using src='${url}'")
 
       @TLS_VERIFY_CODE@
@@ -152,6 +156,11 @@ foreach(i RANGE ${retry_number})
         --- LOG END ---
         "
         )
+      if(NOT status_code IN_LIST download_retry_codes)
+        list(APPEND skip_url_list "${url}")
+        break()
+      endif()
+    endif()
   endif()
   endforeach()
 endforeach()

Tests/RunCMake/ExternalProject/DownloadTimeout-build-result.txt

@@ -0,0 +1 @@
+^[^0]

Tests/RunCMake/ExternalProject/DownloadTimeout-build-stderr.txt

@@ -0,0 +1 @@
+.*

Tests/RunCMake/ExternalProject/DownloadTimeout.cmake

@@ -0,0 +1,5 @@
+include(ExternalProject)
+set(source_dir "${CMAKE_CURRENT_BINARY_DIR}/DownloadTimeout")
+file(REMOVE_RECURSE "${source_dir}")
+file(MAKE_DIRECTORY "${source_dir}")
+ExternalProject_Add(MyProj URL "http://cmake.org/invalid_file.tar.gz")

Tests/RunCMake/ExternalProject/RunCMakeTest.cmake

@@ -38,6 +38,7 @@ set(RunCMake_TEST_OUTPUT_MERGE 0)
 if(NOT RunCMake_GENERATOR MATCHES "Visual Studio")
   __ep_test_with_build(LogOutputOnFailure)
   __ep_test_with_build(LogOutputOnFailureMerged)
+  __ep_test_with_build(DownloadTimeout)
 endif()
 
 # We can't test the substitution when using the old MSYS due to