Merge branch 'jk/relative-directory-fix'

Some codepaths, including the refs API, get and keep relative paths, that go out of sync when the process does chdir(2). The chdir-notify API is introduced to let these codepaths adjust these cached paths to the new current directory. * jk/relative-directory-fix: refs: use chdir_notify to update cached relative paths set_work_tree: use chdir_notify add chdir-notify API trace.c: export trace_setup_key set_git_dir: die when setenv() fails