[PATCH v2 0/5] catfile: introduce NUL-terminated output format

Hi,

this is the second version of my patch series that introduces a new NUL terminated output format to git-cat-file(1) in order to make its output unambiguously parsable in the case where the input contains newlines.

Changes compared to v1:

    - Improved the commit subject of v5 to mention that the new option
      changes both input and output to be NUL delimited.

    - Extended the commit message to make a better case for why `-Z`
      changes both input and output format to be NUL terminated, instead
      of having `-z` change the input and `-Z` change the output format.

    - The `-Z` option is now sorted before `-z` in git-cat-file(1).

    - The `-z` option is now deprecated "even more", where it is hidden
      from the synopsis as well as from the `-h` output.

    - A small change to pass the delimiter to `batch_write()` directly
      instead of storing it in a temporary array first.

Thanks for your feedback, Junio and Phillip!

Patrick

Patrick Steinhardt (5):
  t1006: don't strip timestamps from expected results
  t1006: modernize test style to use `test_cmp`
  strbuf: provide CRLF-aware helper to read until a specified delimiter
  cat-file: simplify reading from standard input
  cat-file: introduce option to delimit input and output with NUL

 Documentation/git-cat-file.txt |  15 +-
 builtin/cat-file.c             |  85 +++++------
 strbuf.c                       |  11 +-
 strbuf.h                       |  12 ++
 t/t1006-cat-file.sh            | 249 +++++++++++++++++++++------------
 5 files changed, 233 insertions(+), 139 deletions(-)

Range-diff against v1:
1:  5c8b4a1d70 = 1:  5c8b4a1d70 t1006: don't strip timestamps from expected results
2:  251fc2a387 = 2:  251fc2a387 t1006: modernize test style to use `test_cmp`
3:  8127eeac97 = 3:  8127eeac97 strbuf: provide CRLF-aware helper to read until a specified delimiter
4:  e7cba8dc4c = 4:  e7cba8dc4c cat-file: simplify reading from standard input
5:  07a7c34615 ! 5:  79ed618c84 cat-file: Introduce new option to delimit output with NUL characters
    @@ Metadata
     Author: Patrick Steinhardt <ps@pks.im>
     
      ## Commit message ##
    -    cat-file: Introduce new option to delimit output with NUL characters
    +    cat-file: introduce option to delimit input and output with NUL
     
         In db9d67f2e9 (builtin/cat-file.c: support NUL-delimited input with
         `-z`, 2022-07-22), we have introduced a new mode to read the input via
    @@ Commit message
         given that revisions containing newlines are quite exotic.
     
         Instead, introduce a new option `-Z` that switches to NUL-delimited
    -    input and output. The old `-z` option is marked as deprecated with a
    -    hint that its output may become unparsable.
    +    input and output. While this new option could arguably only switch the
    +    output format to be NUL-delimited, the consequence would be that users
    +    have to always specify both `-z` and `-Z` when the input may contain
    +    newlines. On the other hand, if the user knows that there never will be
    +    newlines in the input, they don't have to use either of those options.
    +    There is thus no usecase that would warrant treating input and output
    +    format separately, which is why we instead opt to "do the right thing"
    +    and have `-Z` mean to NUL-terminate both formats.
    +
    +    The old `-z` option is marked as deprecated with a hint that its output
    +    may become unparsable. It is thus hidden both from the synopsis as well
    +    as the command's help output.
     
         Co-authored-by: Toon Claes <toon@iotcl.com>
         Signed-off-by: Patrick Steinhardt <ps@pks.im>
    @@ Documentation/git-cat-file.txt: SYNOPSIS
      'git cat-file' (--batch | --batch-check | --batch-command) [--batch-all-objects]
      	     [--buffer] [--follow-symlinks] [--unordered]
     -	     [--textconv | --filters] [-z]
    -+	     [--textconv | --filters] [-z] [-Z]
    ++	     [--textconv | --filters] [-Z]
      'git cat-file' (--textconv | --filters)
      	     [<rev>:<path|tree-ish> | --path=<path|tree-ish> <rev>]
      
     @@ Documentation/git-cat-file.txt: respectively print:
    - -z::
    - 	Only meaningful with `--batch`, `--batch-check`, or
    - 	`--batch-command`; input is NUL-delimited instead of
    -+	newline-delimited. This option is deprecated in favor of
    -+	`-Z` as the output can otherwise be ambiguous.
    -+
    + 	/etc/passwd
    + --
    + 
     +-Z::
     +	Only meaningful with `--batch`, `--batch-check`, or
     +	`--batch-command`; input and output is NUL-delimited instead of
    - 	newline-delimited.
    ++	newline-delimited.
    ++
    + -z::
    + 	Only meaningful with `--batch`, `--batch-check`, or
    + 	`--batch-command`; input is NUL-delimited instead of
    +-	newline-delimited.
    ++	newline-delimited. This option is deprecated in favor of
    ++	`-Z` as the output can otherwise be ambiguous.
      
      
    + OUTPUT
     @@ Documentation/git-cat-file.txt: notdir SP <size> LF
      is printed when, during symlink resolution, a file is used as a
      directory name.
    @@ builtin/cat-file.c: static void batch_object_write(const char *obj_name,
      	batch_write(opt, scratch->buf, scratch->len);
      
      	if (opt->batch_mode == BATCH_MODE_CONTENTS) {
    -+		char buf[] = {opt->output_delim};
      		print_object_or_die(opt, data);
     -		batch_write(opt, "\n", 1);
    -+		batch_write(opt, buf, 1);
    ++		batch_write(opt, &opt->output_delim, 1);
      	}
      }
      
    @@ builtin/cat-file.c: int cmd_cat_file(int argc, const char **argv, const char *pr
      		N_("git cat-file (--batch | --batch-check | --batch-command) [--batch-all-objects]\n"
      		   "             [--buffer] [--follow-symlinks] [--unordered]\n"
     -		   "             [--textconv | --filters] [-z]"),
    -+		   "             [--textconv | --filters] [-z] [-Z]"),
    ++		   "             [--textconv | --filters] [-Z]"),
      		N_("git cat-file (--textconv | --filters)\n"
      		   "             [<rev>:<path|tree-ish> | --path=<path|tree-ish> <rev>]"),
      		NULL
     @@ builtin/cat-file.c: int cmd_cat_file(int argc, const char **argv, const char *prefix)
    + 			N_("like --batch, but don't emit <contents>"),
      			PARSE_OPT_OPTARG | PARSE_OPT_NONEG,
      			batch_option_callback),
    - 		OPT_BOOL('z', NULL, &input_nul_terminated, N_("stdin is NUL-terminated")),
    +-		OPT_BOOL('z', NULL, &input_nul_terminated, N_("stdin is NUL-terminated")),
    ++		OPT_BOOL_F('z', NULL, &input_nul_terminated, N_("stdin is NUL-terminated"),
    ++			PARSE_OPT_HIDDEN),
     +		OPT_BOOL('Z', NULL, &nul_terminated, N_("stdin and stdout is NUL-terminated")),
      		OPT_CALLBACK_F(0, "batch-command", &batch, N_("format"),
      			N_("read commands from stdin"),