Merge topic 'ExternalProject-optimize-git'

c58f5e116e ExternalProject: Extend documentation about GIT_TAG usage
8355665f8d ExternalProject: Drop unnecessary 'git submodule init'
00b5f1a1b5 ExternalProject: Simplify generated 'git clone' scripts
98e6822fdf ExternalProject: Re-run 'git clone' when GIT_REMOTE_NAME changes

Acked-by: Kitware Robot <[email protected]>
Merge-request: !3095

Modules/ExternalProject.cmake

@@ -251,6 +251,9 @@ External Project Definition
           The lack of such deterministic behavior makes the main project lose
           traceability and repeatability.
 
+        If ``GIT_SHALLOW`` is enabled then ``GIT_TAG`` works only with
+        branch names and tags.  A commit hash is not allowed.
+
       ``GIT_REMOTE_NAME <name>``
         The optional name of the remote. If this option is not specified, it
         defaults to ``origin``.
@@ -1053,11 +1056,6 @@ define_property(DIRECTORY PROPERTY "EP_UPDATE_DISCONNECTED" INHERITED
   )
 
 function(_ep_write_gitclone_script script_filename source_dir git_EXECUTABLE git_repository git_tag git_remote_name git_submodules git_shallow git_progress git_config src_name work_dir gitclone_infofile gitclone_stampfile tls_verify)
-  if(NOT GIT_VERSION_STRING VERSION_LESS 1.7.10)
-    set(git_clone_shallow_options "--depth 1 --no-single-branch")
-  else()
-    set(git_clone_shallow_options "--depth 1")
-  endif()
   if(NOT GIT_VERSION_STRING VERSION_LESS 1.8.5)
     # Use `git checkout <tree-ish> --` to avoid ambiguity with a local path.
     set(git_checkout_explicit-- "--")
@@ -1067,12 +1065,30 @@ function(_ep_write_gitclone_script script_filename source_dir git_EXECUTABLE git
     # because that will not search for remote branch names, a common use case.
     set(git_checkout_explicit-- "")
   endif()
-  file(WRITE ${script_filename}
-"if(\"${git_tag}\" STREQUAL \"\")
-  message(FATAL_ERROR \"Tag for git checkout should not be empty.\")
-endif()
+  if("${git_tag}" STREQUAL "")
+    message(FATAL_ERROR "Tag for git checkout should not be empty.")
+  endif()
 
-set(run 0)
+  set(git_clone_options)
+  if(git_shallow)
+    if(NOT GIT_VERSION_STRING VERSION_LESS 1.7.10)
+      list(APPEND git_clone_options "--depth 1 --no-single-branch")
+    else()
+      list(APPEND git_clone_options "--depth 1")
+    endif()
+  endif()
+  if(git_progress)
+    list(APPEND git_clone_options --progress)
+  endif()
+  foreach(config IN LISTS git_config)
+    list(APPEND git_clone_options --config ${config})
+  endforeach()
+  if(NOT ${git_remote_name} STREQUAL "origin")
+    list(APPEND git_clone_options --origin \"${git_remote_name}\")
+  endif()
+  string (REPLACE ";" " " git_clone_options "${git_clone_options}")
+  file(WRITE ${script_filename}
+"set(run 0)
 
 if(\"${gitclone_infofile}\" IS_NEWER_THAN \"${gitclone_stampfile}\")
   set(run 1)
@@ -1100,29 +1116,12 @@ if(NOT \"x${tls_verify}\" STREQUAL \"x\" AND NOT tls_verify)
     -c http.sslVerify=false)
 endif()
 
-set(git_clone_options)
-
-set(git_shallow \"${git_shallow}\")
-if(git_shallow)
-  list(APPEND git_clone_options ${git_clone_shallow_options})
-endif()
-
-set(git_progress \"${git_progress}\")
-if(git_progress)
-  list(APPEND git_clone_options --progress)
-endif()
-
-set(git_config \"${git_config}\")
-foreach(config IN LISTS git_config)
-  list(APPEND git_clone_options --config \${config})
-endforeach()
-
 # try the clone 3 times in case there is an odd git clone issue
 set(error_code 1)
 set(number_of_tries 0)
 while(error_code AND number_of_tries LESS 3)
   execute_process(
-    COMMAND \"${git_EXECUTABLE}\" \${git_options} clone \${git_clone_options} --origin \"${git_remote_name}\" \"${git_repository}\" \"${src_name}\"
+    COMMAND \"${git_EXECUTABLE}\" \${git_options} clone ${git_clone_options} \"${git_repository}\" \"${src_name}\"
     WORKING_DIRECTORY \"${work_dir}\"
     RESULT_VARIABLE error_code
     )
@@ -1145,15 +1144,6 @@ if(error_code)
   message(FATAL_ERROR \"Failed to checkout tag: '${git_tag}'\")
 endif()
 
-execute_process(
-  COMMAND \"${git_EXECUTABLE}\" \${git_options} submodule init ${git_submodules}
-  WORKING_DIRECTORY \"${work_dir}/${src_name}\"
-  RESULT_VARIABLE error_code
-  )
-if(error_code)
-  message(FATAL_ERROR \"Failed to init submodules in: '${work_dir}/${src_name}'\")
-endif()
-
 execute_process(
   COMMAND \"${git_EXECUTABLE}\" \${git_options} submodule update --recursive --init ${git_submodules}
   WORKING_DIRECTORY \"${work_dir}/${src_name}\"
@@ -2460,7 +2450,7 @@ function(_ep_add_download_command name)
     #
     set(repository ${git_repository})
     set(module)
-    set(tag)
+    set(tag ${git_remote_name})
     configure_file(
       "${CMAKE_ROOT}/Modules/RepositoryInfo.txt.in"
       "${stamp_dir}/${name}-gitinfo.txt"