[PATCH 0/5] cat-file: introduce NUL-terminated output format

Hi,

with Git v2.38.0, we have introduced the `-z` option to git-cat-file(1) that causes it to read NUL-terminated queries from standard input instead of the newline-terminated queries. This fixes issues when the query themselves contains a newline, like it can happen if e.g. we need to pass a path-scoped revision with embedded newlines.

Unfortunately, this change is causing a new problem. When the object cannot be looked up, then we print an error message that echoes the input:

``` $ echo does-not-exist | git cat-file --batch does-not-exist missing ```

Now if the input itself contains newlines then the output can become inherently unparsable:

```
$ printf "7ce4f05bae8120d9fa258e854a8669f6ea9cb7b1 blob 10\n1234567890\n\n\commit000" |
    git cat-file --batch -z
7ce4f05bae8120d9fa258e854a8669f6ea9cb7b1 blob 10
1234567890

commit missing ```

Ideally, `-z` should have also switched the output to be NUL-terminated. But it didn't, and we cannot change this issue now without doing a backwards incompatible change. Instead, this series introduces a new `-Z` mode that switches both input and output to be NUL-terminated to fix the issue.

Note that Toon has sent a patch series for this issue to address the same issue, see the thread starting at [1]. I've collaborated with him internally at GitLab to arrive at this new patch series which thus effectively supersedes the patches he has sent. The approach is also different: while his patches start quoting the output, the approach chosen by my series only changes the lines to be NUL terminated. This should make it easier to use for scripted purposes compared to having to de-quote the input.

I've put all folks that participated in the original thread into Cc.

Patrick

[1]: <20221209150048.2400648-1-toon@iotcl.com>

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 new option to delimit output with NUL characters

 Documentation/git-cat-file.txt |  13 +-
 builtin/cat-file.c             |  85 +++++------
 strbuf.c                       |  11 +-
 strbuf.h                       |  12 ++
 t/t1006-cat-file.sh            | 249 +++++++++++++++++++++------------
 5 files changed, 232 insertions(+), 138 deletions(-)