Merge branch 'jk/prefix-filename'

Code clean-up with minor bugfixes.

* jk/prefix-filename:
bundle: use prefix_filename with bundle path
prefix_filename: simplify windows #ifdef
prefix_filename: return newly allocated string
prefix_filename: drop length parameter
prefix_filename: move docstring to header file
hash-object: fix buffer reuse with --path in a subdirectory

diff --cc builtin/rev-parse.c
Simple merge

diff --cc cache.h
Simple merge