Re: [PATCH v8 3/7] progress.c tests: make start/stop commands on stdin

> Change the usage of the "test-tool progress" introduced in
> 2bb74b53a49 (Test the progress display, 2019-09-16) to take command
> like "start" and "stop" on stdin, instead of running them implicitly.
> 
> This makes for tests that are easier to read, since the recipe will
> mirror the API usage, and allows for easily testing invalid usage that
> would yield (or should yield) a BUG(), e.g. providing two "start"
> calls in a row. A subsequent commit will add such tests.
> 
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---
>  t/helper/test-progress.c    | 46 ++++++++++++++++++++++-------
>  t/t0500-progress-display.sh | 58 +++++++++++++++++++++++--------------
>  2 files changed, 72 insertions(+), 32 deletions(-)
> 
> diff --git a/t/helper/test-progress.c b/t/helper/test-progress.c
> index 50fd3be3dad..becc163375f 100644
> --- a/t/helper/test-progress.c
> +++ b/t/helper/test-progress.c
> @@ -3,6 +3,9 @@
>   *
>   * Reads instructions from standard input, one instruction per line:
>   *
> + *   "start <total>[ <title>]" - Call start_progress(title, total),
> + *                               Uses the default title of "Working hard"
> + *                               if the " <title>" is omitted.
>   *   "progress <items>" - Call display_progress() with the given item count
>   *                        as parameter.
>   *   "throughput <bytes> <millis> - Call display_throughput() with the given
> @@ -10,6 +13,7 @@
>   *                                  specify the time elapsed since the
>   *                                  start_progress() call.
>   *   "update" - Set the 'progress_update' flag.
> + *   "stop" - Call stop_progress().
>   *
>   * See 't0500-progress-display.sh' for examples.
>   */
> @@ -19,34 +23,52 @@
>  #include "parse-options.h"
>  #include "progress.h"
>  #include "strbuf.h"
> +#include "string-list.h"
>  
>  int cmd__progress(int argc, const char **argv)
>  {
> -	int total = 0;
> -	const char *title;
> +	const char *const default_title = "Working hard";
> +	struct string_list titles = STRING_LIST_INIT_DUP;
>  	struct strbuf line = STRBUF_INIT;
> -	struct progress *progress;
> +	struct progress *progress = NULL;
>  
>  	const char *usage[] = {
> -		"test-tool progress [--total=<n>] <progress-title>",
> +		"test-tool progress <stdin",
>  		NULL
>  	};
>  	struct option options[] = {
> -		OPT_INTEGER(0, "total", &total, "total number of items"),
>  		OPT_END(),
>  	};
>  
>  	argc = parse_options(argc, argv, NULL, options, usage, 0);
> -	if (argc != 1)
> -		die("need a title for the progress output");
> -	title = argv[0];
> +	if (argc)
> +		usage_with_options(usage, options);
>  
>  	progress_testing = 1;
> -	progress = start_progress(title, total);
>  	while (strbuf_getline(&line, stdin) != EOF) {
>  		char *end;
>  
> -		if (skip_prefix(line.buf, "progress ", (const char **) &end)) {
> +		if (skip_prefix(line.buf, "start ", (const char **) &end)) {
> +			uint64_t total = strtoull(end, &end, 10);
> +			const char *title;
> +			const char *str;
> +
> +			/*
> +			 * We can't use "end + 1" as an argument to
> +			 * start_progress(), it doesn't xstrdup() its
> +			 * "title" argument. We need to hold onto a
> +			 * valid "char *" for it until the end.
> +			 */
> +			if (!*end)
> +				title = default_title;
> +			else if (*end == ' ')
> +				title = string_list_insert(&titles, end + 1)->string;
> +			else
> +				die("invalid input: '%s'\n", line.buf);
> +
> +			str = title ? title : default_title;

> +			progress = start_progress(str, total);
> +		} else if (skip_prefix(line.buf, "progress ", (const char **) &end)) {
>  			uint64_t item_count = strtoull(end, &end, 10);
>  			if (*end != '\0')
>  				die("invalid input: '%s'\n", line.buf);