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builtin/cat-file.c: support NUL-delimited input with -z

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When callers are using `cat-file` via one of the stdin-driven `--batch`
modes, all input is newline-delimited. This presents a problem when
callers wish to ask about, e.g. tree-entries that have a newline
character present in their filename.

To support this niche scenario, introduce a new `-z` mode to the
`--batch`, `--batch-check`, and `--batch-command` suite of options that
instructs `cat-file` to treat its input as NUL-delimited, allowing the
individual commands themselves to have newlines present.

The refactoring here is slightly unfortunate, since we turn loops like:

    while (strbuf_getline(&buf, stdin) != EOF)

into:

    while (1) {
        int ret;
        if (opt->nul_terminated)
            ret = strbuf_getline_nul(&input, stdin);
        else
            ret = strbuf_getline(&input, stdin);

        if (ret == EOF)
            break;
    }

It's tempting to think that we could use `strbuf_getwholeline()` and
specify either `\n` or `\0` as the terminating character. But for input
on platforms that include a CR character preceeding the LF, this
wouldn't quite be the same, since `strbuf_getline(...)` will trim any
trailing CR, while `strbuf_getwholeline(&buf, stdin, '\n')` will not.

In the future, we could clean this up further by introducing a variant
of `strbuf_getwholeline()` that addresses the aforementioned gap, but
that approach felt too heavy-handed for this pair of uses.

Some tests are added in t1006 to ensure that `cat-file` produces the
same output in `--batch`, `--batch-check`, and `--batch-command` modes
with and without the new `-z` option.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Taylor Blau
2022-07-22 19:29:05 -04:00
committed by Junio C Hamano
parent 3639fefe7d
commit db9d67f2e9
3 changed files with 72 additions and 5 deletions
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28
builtin/cat-file.c
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@ -31,6 +31,7 @@ struct batch_options {
int all_objects;
int unordered;
int transform_mode; /* may be 'w' or 'c' for --filters or --textconv */
int nul_terminated;
const char *format;
};
@ -614,12 +615,20 @@ static void batch_objects_command(struct batch_options *opt,
struct queued_cmd *queued_cmd = NULL;
size_t alloc = 0, nr = 0;
while (!strbuf_getline(&input, stdin)) {
int i;
while (1) {
int i, ret;
const struct parse_cmd *cmd = NULL;
const char *p = NULL, *cmd_end;
struct queued_cmd call = {0};
if (opt->nul_terminated)
ret = strbuf_getline_nul(&input, stdin);
else
ret = strbuf_getline(&input, stdin);
if (ret)
break;
if (!input.len)
die(_("empty command in input"));
if (isspace(*input.buf))
@ -763,7 +772,16 @@ static int batch_objects(struct batch_options *opt)
goto cleanup;
}
while (strbuf_getline(&input, stdin) != EOF) {
while (1) {
int ret;
if (opt->nul_terminated)
ret = strbuf_getline_nul(&input, stdin);
else
ret = strbuf_getline(&input, stdin);
if (ret == EOF)
break;
if (data.split_on_whitespace) {
/*
* Split at first whitespace, tying off the beginning
@ -866,6 +884,7 @@ 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, &batch.nul_terminated, N_("stdin is NUL-terminated")),
OPT_CALLBACK_F(0, "batch-command", &batch, N_("format"),
N_("read commands from stdin"),
PARSE_OPT_OPTARG | PARSE_OPT_NONEG,
@ -921,6 +940,9 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
else if (batch.all_objects)
usage_msg_optf(_("'%s' requires a batch mode"), usage, options,
"--batch-all-objects");
else if (batch.nul_terminated)
usage_msg_optf(_("'%s' requires a batch mode"), usage, options,
"-z");
/* Batch defaults */
if (batch.buffer_output < 0)