Merge branch 'jk/long-error-messages'

The codepath to produce error messages had a hard-coded limit to
the size of the message, primarily to avoid memory allocation while
calling die().

* jk/long-error-messages:
vreportf: avoid intermediate buffer
vreportf: report to arbitrary filehandles

diff --cc git-compat-util.h
Simple merge

diff --cc run-command.c
Simple merge