cat-file: simplify reading from standard input

The batch modes of git-cat-file(1) read queries from stantard input that
are either newline- or NUL-delimited. This code was introduced via
db9d67f (builtin/cat-file.c: support NUL-delimited input with `-z`,
2022-07-22), which notes that:

"""
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;
     }
"""

The commit proposed introducing a helper function that is easier to use,
which is just what we have done in the preceding commit. Refactor the
code to use this new helper to simplify the loop.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

builtin/cat-file.c

@@ -42,7 +42,7 @@ struct batch_options {
 	int all_objects;
 	int unordered;
 	int transform_mode; /* may be 'w' or 'c' for --filters or --textconv */
-	int nul_terminated;
+	char input_delim;
 	const char *format;
 };
 
@@ -694,20 +694,12 @@ static void batch_objects_command(struct batch_options *opt,
 	struct queued_cmd *queued_cmd = NULL;
 	size_t alloc = 0, nr = 0;
 
-	while (1) {
-		int i, ret;
+	while (strbuf_getdelim_strip_crlf(&input, stdin, opt->input_delim) != EOF) {
+		int i;
 		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))
@@ -851,16 +843,7 @@ static int batch_objects(struct batch_options *opt)
 		goto cleanup;
 	}
 
-	while (1) {
-		int ret;
-		if (opt->nul_terminated)
-			ret = strbuf_getline_nul(&input, stdin);
-		else
-			ret = strbuf_getline(&input, stdin);
-
-		if (ret == EOF)
-			break;
-
+	while (strbuf_getdelim_strip_crlf(&input, stdin, opt->input_delim) != EOF) {
 		if (data.split_on_whitespace) {
 			/*
 			 * Split at first whitespace, tying off the beginning
@@ -929,6 +912,7 @@ int cmd_cat_file(int argc, const char **argv, const char *prefix)
 	const char *exp_type = NULL, *obj_name = NULL;
 	struct batch_options batch = {0};
 	int unknown_type = 0;
+	int input_nul_terminated = 0;
 
 	const char * const usage[] = {
 		N_("git cat-file <type> <object>"),
@@ -965,7 +949,7 @@ 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_BOOL('z', NULL, &input_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,
@@ -1024,10 +1008,12 @@ 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)
+	else if (input_nul_terminated)
 		usage_msg_optf(_("'%s' requires a batch mode"), usage, options,
 			       "-z");
 
+	batch.input_delim = input_nul_terminated ? '\0' : '\n';
+
 	/* Batch defaults */
 	if (batch.buffer_output < 0)
 		batch.buffer_output = batch.all_objects;