[PATCH v2 00/31] libify mailinfo and call it directly from am

During the discussion on the recent "git am" regression, I noticed that the command reimplemented in C spawns one "mailsplit" and then spawns "mailinfo" followed by "apply --index" to commit the changes described in each message. As there are platforms where spawning subprocess via run_command() interface is heavy-weight, something that is conceptually very simple like "mailinfo" is better called directly inside the process---something that is lightweight and frequently used is where the overhead of run_command() would be felt most.

And here is that topic, slightly reordered and polished up, since yesterday's version.

 - The series no longer depends on an unrelated "how about this" patch
   to mailinfo.

 - Fixes are moved to earlier spots in the series.

 - Error checking in the endgame patch has been tightened.

Junio C Hamano (31):
  mailinfo: remove a no-op call convert_to_utf8(it, "")
  mailinfo: fix for off-by-one error in boundary stack
  mailinfo: explicitly close file handle to the patch output
  mailinfo: fold decode_header_bq() into decode_header()
  mailinfo: move handle_boundary() lower
  mailinfo: get rid of function-local static states
  mailinfo: always pass "line" as an argument
  mailinfo: move global "line" into mailinfo() function
  mailinfo: introduce "struct mailinfo" to hold globals
  mailinfo: move keep_subject & keep_non_patch_bracket to struct mailinfo
  mailinfo: move global "FILE *fin, *fout" to struct mailinfo
  mailinfo: move filter/header stage to struct mailinfo
  mailinfo: move patch_lines to struct mailinfo
  mailinfo: move add_message_id and message_id to struct mailinfo
  mailinfo: move use_scissors and use_inbody_headers to struct mailinfo
  mailinfo: move metainfo_charset to struct mailinfo
  mailinfo: move transfer_encoding to struct mailinfo
  mailinfo: move charset to struct mailinfo
  mailinfo: handle_commit_msg() shouldn't be called after finding patchbreak
  mailinfo: move cmitmsg and patchfile to struct mailinfo
  mailinfo: move [ps]_hdr_data to struct mailinfo
  mailinfo: keep the parsed log message in a strbuf
  mailinfo: move content/content_top to struct mailinfo
  mailinfo: move read_one_header_line() closer to its callers
  mailinfo: move check_header() after the helpers it uses
  mailinfo: move cleanup_space() before its users
  mailinfo: move definition of MAX_HDR_PARSED to closer to its use
  mailinfo: libify
  mailinfo: handle charset conversion errors in the caller
  mailinfo: remove calls to exit() and die() deep in the callchain
  am: make direct call to mailinfo

 Makefile           |    1 +
 builtin/am.c       |   42 ++-
 builtin/mailinfo.c | 1055 +---------------------------------------------------
 mailinfo.c         | 1024 ++++++++++++++++++++++++++++++++++++++++++++++++++
 mailinfo.h         |   41 ++
 5 files changed, 1109 insertions(+), 1054 deletions(-)
 create mode 100644 mailinfo.c
 create mode 100644 mailinfo.h