Merge branch 'sb/filenames-with-dashes'

Rename bunch of source files to more consistently use dashes instead of underscores to connect words. * sb/filenames-with-dashes: replace_object.c: rename to use dash in file name sha1_file.c: rename to use dash in file name sha1_name.c: rename to use dash in file name exec_cmd: rename to use dash in file name unicode_width.h: rename to use dash in file name write_or_die.c: rename to use dashes in file name