Add ecm_win_resolve_symlinks module.v5.28.0-rc2

REVIEW: 128112
(cherry picked from commit 632b8868de38e2f85fb4969bcae3dd89a2a0695c)

1 files changed, 144 insertions, 0 deletions

diff --git a/modules/ECMWinResolveSymlinks.cmake b/modules/ECMWinResolveSymlinks.cmake
new file mode 100644
index 00000000..d9444663
--- /dev/null
+++ b/modules/ECMWinResolveSymlinks.cmake
@@ -0,0 +1,144 @@
+#.rst:
+# ECMWinResolveSymlinks
+# --------------------------
+#
+# Resolve pseudo-symlinks created by git when cloning on Windows.
+#
+# ::
+#
+#   ecm_win_resolve_symlinks(<dir>)
+#
+# When git checks out a repository with UNIX symlinks on Windows machine,
+# it creates a text file for each symlink, containing a relative path to the
+# real file.
+# This function would recursively walk over specified directory and replace
+# pseudo-symlinks with corresponding real file's contents. It would then run
+# git update-index --assume-unchanged on them to trick git.
+#
+# This is useful for projects like "breeze-icons" that contain many identical
+# icons implemented as symlinks.
+#
+# Since 5.28
+
+#=============================================================================
+# Copyright 2016 Gleb Popov <6yearold@gmail.com>
+#
+# Distributed under the OSI-approved BSD License (the "License");
+# see accompanying file COPYING-CMAKE-SCRIPTS for details.
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+# (To distribute this file outside of extra-cmake-modules, substitute the full
+#  License text for the above reference.)
+
+function(ECM_WIN_RESOLVE_SYMLINKS _dir)
+  get_filename_component(dir ${_dir} ABSOLUTE)
+  find_program(GIT_EXECUTABLE git)
+  if(NOT GIT_EXECUTABLE)
+    message(SEND_ERROR "Git executable not found!")
+  endif()
+
+  message(STATUS "Resolving symlinks in ${dir}...")
+  _find_symlinks(${dir} symlinks)
+  _portioned_list(symlinks ${symlinks})
+  foreach(s IN LISTS symlinks)
+    string(REPLACE ":" ";" s ${s})
+    _assume_unchanged(NO ${dir} "${s}")
+    _checkout_symlinks(${dir} "${s}")
+    _resolve_symlinks(${dir} "${s}")
+    _assume_unchanged(YES ${dir} "${s}")
+  endforeach()
+  message(STATUS "Resolving symlinks in ${dir}... Done.")
+
+  # touch cache every build to force CMake to re-run these functions everytime
+  if(NOT TARGET wrs_touch_cache)
+    add_custom_target(wrs_touch_cache ALL
+      COMMAND ${CMAKE_COMMAND} -E touch ${CMAKE_BINARY_DIR}/CMakeCache.txt
+    )
+  endif()
+endfunction()
+
+function(_assume_unchanged mode dir symlinks)
+  if(mode)
+    set(flag --assume-unchanged)
+  else()
+    set(flag --no-assume-unchanged)
+  endif()
+
+  execute_process(COMMAND ${GIT_EXECUTABLE} update-index ${flag} ${symlinks}
+    WORKING_DIRECTORY ${dir}
+  )
+endfunction()
+
+function(_find_symlinks dir outvar)
+  execute_process(COMMAND ${GIT_EXECUTABLE} ls-files -s
+    WORKING_DIRECTORY ${dir}
+    OUTPUT_VARIABLE out
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+  )
+
+  set(${outvar})
+  if(out)
+    string(REPLACE "\n" ";" out ${out})
+
+    foreach(f IN LISTS out)
+      # 120000 0db97052931e18484b6705f3bc644484ef9403b0 0 <tab> icons-dark/actions/16/CVnamespace.svg
+      string(REPLACE "\t" ";" f "${f}")
+      string(REPLACE " " ";" f "${f}")
+      list(GET f 0 mode)
+      if(mode STREQUAL "120000")
+        list(GET f 3 symlink)
+        list(APPEND ${outvar} ${symlink})
+      endif()
+    endforeach()
+  endif()
+  set(${outvar} ${${outvar}} PARENT_SCOPE)
+endfunction()
+
+# In functions like _checkout_symlinks() the command line can become too lengthy for Windows.
+# So we partition it, but in a hacky way due to CMake doesn't have list of lists.
+function(_portioned_list outvar)
+  list(LENGTH ARGN arglen)
+
+  if(arglen EQUAL 0)
+    set(${outvar} "" PARENT_SCOPE)
+    return()
+  endif()
+
+  set(init)
+  set(tail)
+  math(EXPR range "${arglen} - 1")
+  foreach(i RANGE ${range})
+    list(GET ARGN ${i} v)
+    string(LENGTH "${init}" initlen)
+    string(LENGTH ${v} vlen)
+    math(EXPR sumlen "${initlen} + ${vlen}")
+    if(sumlen LESS 8192)
+      list(APPEND init ${v})
+    else()
+      list(APPEND tail ${v})
+    endif()
+  endforeach()
+
+  _portioned_list(tail_portioned ${tail})
+  string(REPLACE ";" ":" init "${init}") # Generally this is not safe, because filepath can contain ':' character. But not on Windows. Phew.
+  set(${outvar} ${init} ${tail_portioned} PARENT_SCOPE)
+endfunction()
+
+function(_checkout_symlinks dir symlinks)
+  execute_process(COMMAND ${GIT_EXECUTABLE} checkout ${symlinks}
+    WORKING_DIRECTORY ${dir}
+  )
+endfunction()
+
+function(_resolve_symlinks dir symlinks)
+  foreach(s IN LISTS symlinks)
+    file(READ ${dir}/${s} sdata)
+    get_filename_component(sdir ${dir}/${s} DIRECTORY)
+    set(f "${sdir}/${sdata}")
+    file(READ ${f} fdata)
+    file(WRITE ${dir}/${s} ${fdata})
+  endforeach()
+endfunction()