Re: [PATCH v2 1/8] for-each-ref: add --stdin option

> From: Derrick Stolee <derrickstolee@github.com>
> 
> When a user wishes to input a large list of patterns to 'git
> for-each-ref' (likely a long list of exact refs) there are frequently
> system limits on the number of command-line arguments.
> 
> Add a new --stdin option to instead read the patterns from standard
> input. Add tests that check that any unrecognized arguments are
> considered an error when --stdin is provided. Also, an empty pattern
> list is interpreted as the complete ref set.
> 
> When reading from stdin, we populate the filter.name_patterns array
> dynamically as opposed to pointing to the 'argv' array directly. This
> requires a careful cast while freeing the individual strings,
> conditioned on the --stdin option.

> Signed-off-by: Derrick Stolee <derrickstolee@github.com>
> ---
>   Documentation/git-for-each-ref.txt |  7 +++++-
>   builtin/for-each-ref.c             | 29 ++++++++++++++++++++++-
>   t/t6300-for-each-ref.sh            | 37 ++++++++++++++++++++++++++++++
>   3 files changed, 71 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
> index 6da899c6296..ccdc2911bb9 100644
> --- a/Documentation/git-for-each-ref.txt
> +++ b/Documentation/git-for-each-ref.txt
> @@ -9,7 +9,8 @@ SYNOPSIS
>   --------
>   [verse]
>   'git for-each-ref' [--count=<count>] [--shell|--perl|--python|--tcl]
> -		   [(--sort=<key>)...] [--format=<format>] [<pattern>...]
> +		   [(--sort=<key>)...] [--format=<format>]
> +		   [ --stdin | <pattern>... ]
>   		   [--points-at=<object>]
>   		   [--merged[=<object>]] [--no-merged[=<object>]]
>   		   [--contains[=<object>]] [--no-contains[=<object>]]
> @@ -32,6 +33,10 @@ OPTIONS
>   	literally, in the latter case matching completely or from the
>   	beginning up to a slash.
>   
> +--stdin::
> +	If `--stdin` is supplied, then the list of patterns is read from
> +	standard input instead of from the argument list.
> +
>   --count=<count>::
>   	By default the command shows all refs that match
>   	`<pattern>`.  This option makes it stop after showing
> diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
> index 6f62f40d126..e005a7ef3ce 100644
> --- a/builtin/for-each-ref.c
> +++ b/builtin/for-each-ref.c
> @@ -25,6 +25,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
>   	struct ref_format format = REF_FORMAT_INIT;
>   	struct strbuf output = STRBUF_INIT;
>   	struct strbuf err = STRBUF_INIT;
> +	int from_stdin = 0;
>   
>   	struct option opts[] = {
>   		OPT_BIT('s', "shell", &format.quote_style,
> @@ -49,6 +50,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
>   		OPT_CONTAINS(&filter.with_commit, N_("print only refs which contain the commit")),
>   		OPT_NO_CONTAINS(&filter.no_commit, N_("print only refs which don't contain the commit")),
>   		OPT_BOOL(0, "ignore-case", &icase, N_("sorting and filtering are case insensitive")),
> +		OPT_BOOL(0, "stdin", &from_stdin, N_("read reference patterns from stdin")),
>   		OPT_END(),
>   	};
>   
> @@ -75,7 +77,27 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
>   	ref_sorting_set_sort_flags_all(sorting, REF_SORTING_ICASE, icase);
>   	filter.ignore_case = icase;
>   
> -	filter.name_patterns = argv;
> +	if (from_stdin) {
> +		struct strbuf line = STRBUF_INIT;
> +		size_t nr = 0, alloc = 16;
> +
> +		if (argv[0])
> +			die(_("unknown arguments supplied with --stdin"));
> +
> +		CALLOC_ARRAY(filter.name_patterns, alloc);
> +
> +		while (strbuf_getline(&line, stdin) != EOF) {
> +			ALLOC_GROW(filter.name_patterns, nr + 1, alloc);
> +			filter.name_patterns[nr++] = strbuf_detach(&line, NULL);
> +		}
> +
> +		/* Add a terminating NULL string. */
> +		ALLOC_GROW(filter.name_patterns, nr + 1, alloc);
> +		filter.name_patterns[nr + 1] = NULL;
> +	} else {
> +		filter.name_patterns = argv;
> +	}
> +
>   	filter.match_as_path = 1;
>   	filter_refs(&array, &filter, FILTER_REFS_ALL);
>   	ref_array_sort(sorting, &array);
> @@ -97,5 +119,10 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
>   	free_commit_list(filter.with_commit);
>   	free_commit_list(filter.no_commit);
>   	ref_sorting_release(sorting);
> +	if (from_stdin) {
> +		for (size_t i = 0; filter.name_patterns[i]; i++)
> +			free((char *)filter.name_patterns[i]);
> +		free(filter.name_patterns);
> +	}
>   	return 0;
>   }
> diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
> index c466fd989f1..a58053a54c5 100755
> --- a/t/t6300-for-each-ref.sh
> +++ b/t/t6300-for-each-ref.sh
> @@ -1464,4 +1464,41 @@ sig_crlf="$(printf "%s" "$sig" | append_cr; echo dummy)"
>   sig_crlf=${sig_crlf%dummy}
>   test_atom refs/tags/fake-sig-crlf contents:signature "$sig_crlf"
>   
> +test_expect_success 'git for-each-ref --stdin: empty' '
> +	>in &&
> +	git for-each-ref --format="%(refname)" --stdin <in >actual &&
> +	git for-each-ref --format="%(refname)" >expect &&
> +	test_cmp expect actual
> +'
> +
> +test_expect_success 'git for-each-ref --stdin: fails if extra args' '
> +	>in &&
> +	test_must_fail git for-each-ref --format="%(refname)" \
> +		--stdin refs/heads/extra <in 2>err &&
> +	grep "unknown arguments supplied with --stdin" err
> +'
> +
> +test_expect_success 'git for-each-ref --stdin: matches' '
> +	cat >in <<-EOF &&
> +	refs/tags/multi*
> +	refs/heads/amb*
> +	EOF
> +
> +	cat >expect <<-EOF &&
> +	refs/heads/ambiguous
> +	refs/tags/multi-ref1-100000-user1
> +	refs/tags/multi-ref1-100000-user2
> +	refs/tags/multi-ref1-200000-user1
> +	refs/tags/multi-ref1-200000-user2
> +	refs/tags/multi-ref2-100000-user1
> +	refs/tags/multi-ref2-100000-user2
> +	refs/tags/multi-ref2-200000-user1
> +	refs/tags/multi-ref2-200000-user2
> +	refs/tags/multiline
> +	EOF
> +
> +	git for-each-ref --format="%(refname)" --stdin <in >actual &&
> +	test_cmp expect actual
> +'
> +
>   test_done