Detecting when the cache is dirty (#284)

* Check that the cache working directory is clean

* cpm_check_working_dir_is_clean for non git repo will not terminate cmake

* sileneced check for git repo, in case of error

* style(CPM.cmake): fixed indentation for ERROR_QUIET

* refactor(CPM.cmake): added logic to handle a cache folder inside a (not correlated) git repo

this is accomplished by checking if we are in the directory where .git lives

* style(CPM.cmake): stray tab to spaces

* test(dirty-cache-check): added unit test to check cpm_check_working_dir_is_clean

the test creates a file in a folder and then uses git to create a repo in that folder, to check various conditions

* Update test/unit/dirty-cache-check.cmake

added user.name and user.email to comply with test machine where git is not completely configured

Co-authored-by: Lars Melchior <TheLartians@users.noreply.github.com>

* feat(cpm_check_working_dir_is_clean): now it takes a git tag (works with hashes too) to check for uncommitted and commited changes

* refactor(cpm_check_working_dir_is_clean): early return for the most common case of uncommited changes in a repo

* refactor(cpm_check_git_working_dir_is_clean): removed edgecase detection (a non-git folder in an unrelated git repo)

now the contract is that com_check_git_working_dir_is_clean is given the base folder of a git repo

Co-authored-by: Andrew Gribble <ag131012@renishaw.com>
Co-authored-by: Lars Melchior <TheLartians@users.noreply.github.com>

test/unit/dirty-cache-check.cmake

@@ -0,0 +1,49 @@
+include(${CPM_PATH}/CPM.cmake)
+include(${CPM_PATH}/testing.cmake)
+
+set(baseDir "${CMAKE_CURRENT_BINARY_DIR}/test_dirty_cache")
+
+find_package(Git REQUIRED)
+
+function(git_do dir)
+  execute_process(
+    COMMAND ${GIT_EXECUTABLE} -c user.name='User' -c user.email='user@email.org' ${ARGN}
+    RESULT_VARIABLE result
+    OUTPUT_VARIABLE status
+    OUTPUT_STRIP_TRAILING_WHITESPACE
+    WORKING_DIRECTORY "${dir}"
+  )
+  if(result)
+    message(FATAL_ERROR "git ${ARGN} fail: ${result} ${status}")
+  endif()
+endfunction()
+
+file(MAKE_DIRECTORY "${baseDir}")
+
+file(WRITE "${baseDir}/draft.txt" "this is a test")
+
+git_do("${baseDir}" init -b main)
+git_do("${baseDir}" commit --allow-empty -m "empty repo")
+message(STATUS "empty repo with file")
+cpm_check_git_working_dir_is_clean(${baseDir} HEAD emptygit_test)
+assert_falsy(emptygit_test)
+
+git_do("${baseDir}" add draft.txt)
+git_do("${baseDir}" commit -m "test change")
+git_do("${baseDir}" tag v0.0.0)
+message(STATUS "commit a change")
+cpm_check_git_working_dir_is_clean(${baseDir} v0.0.0 onecommit_test)
+assert_truthy(onecommit_test)
+
+file(WRITE "${baseDir}/draft.txt" "a modification")
+message(STATUS "dirty repo")
+cpm_check_git_working_dir_is_clean(${baseDir} v0.0.0 nonemptygit_test)
+assert_falsy(nonemptygit_test)
+
+git_do("${baseDir}" add draft.txt)
+git_do("${baseDir}" commit -m "another change")
+message(STATUS "repo clean")
+cpm_check_git_working_dir_is_clean(${baseDir} v0.0.0 twocommit_test)
+assert_falsy(twocommit_test)
+
+file(REMOVE_RECURSE "${baseDir}")