Our file utils functions all have a "futils" prefix, e.g.
`git_futils_touch`. One would thus naturally guess that their
definitions and implementation would live in files "futils.h" and
"futils.c", respectively, but in fact they live in "fileops.h".

Rename the files to match expectations.

When dealing with `core.proectNTFS` and `core.protectHFS` we do check
against `.gitmodules` but we still have a failing test as the non-filesystem
codepath does not check for it.

We want to reject these as they cause compatibility issues and can lead to git
writing to files outside of the repository.

Symbolic links that abuse case insensitivity to write into .git.

Validate HFS ignored char ".git" paths when `core.protectHFS` is
specified.  Validate NTFS invalid ".git" paths when `core.protectNTFS`
is specified.

HFS filesystems ignore some characters like U+200C.  When these
characters are included in a path, they will be ignored for the
purposes of comparison with other paths.  Thus, if you have a ".git"
folder, a folder of ".git<U+200C>" will also match.  Protect our
".git" folder by ensuring that ".git<U+200C>" and friends do not match it.

Disallow:
 1. paths with trailing dot
 2. paths with trailing space
 3. paths with trailing colon
 4. paths that are 8.3 short names of .git folders ("GIT~1")
 5. paths that are reserved path names (COM1, LPT1, etc).
 6. paths with reserved DOS characters (colons, asterisks, etc)

These paths would (without \\?\ syntax) be elided to other paths - for
example, ".git." would be written as ".git".  As a result, writing these
paths literally (using \\?\ syntax) makes them hard to operate with from
the shell, Windows Explorer or other tools.  Disallow these.