All subcommands that take pathspecs mishandled an in-tree symbolic
link when given it as a full path from the root (which arguably is
a sick way to use pathspecs). "git ls-files -s $(pwd)/RelNotes" in
our tree is an easy reproduction recipe.
* mw/symlinks:
setup: don't dereference in-tree symlinks for absolute paths
setup: add abspath_part_inside_repo() function
t0060: add tests for prefix_path when path begins with work tree
t0060: add test for prefix_path when path == work tree
t0060: add test for prefix_path on symlinks via absolute paths
t3004: add test for ls-files on symlinks via absolute paths