Currently there are two functions for formatting trailers in <trailer.h>: void format_trailers(const struct process_trailer_options *, struct list_head *trailers, FILE *outfile); void format_trailers_from_commit(struct strbuf *out, const char *msg, const struct process_trailer_options *opts); and although they are similar enough (even taking the same process_trailer_options struct pointer) they are used quite differently. One might intuitively think that format_trailers_from_commit() builds on top of format_trailers(), but this is not the case. Instead format_trailers_from_commit() calls format_trailer_info() and format_trailers() is never called in that codepath. This is a preparatory refactor to help us deprecate format_trailers() in favor of format_trailer_info() (at which point we can rename the latter to the former). When the deprecation is complete, both format_trailers_from_commit(), and the interpret-trailers builtin will be able to call into the same helper function (instead of format_trailers() and format_trailer_info(), respectively). Unifying the formatters is desirable because it simplifies the API. Reorder parameters for format_trailers_from_commit() to prefer const struct process_trailer_options *opts as the first parameter, because these options are intimately tied to formatting trailers. And take struct strbuf *out last, because it's an "out parameter" (something that the caller wants to use as the output of this function). Similarly, reorder parameters for format_trailer_info(), because later on we will unify the two together. Signed-off-by: Linus Arver <linusa@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>