Subject: Re: [PATCH] grep: provide pathspecs/patterns via file or stdin

From: Denton Liu <[email-masked]>
Date: Thu, 21 Nov 2019 18:14:20 -0800

Hi Emily,

On Thu, Nov 21, 2019 at 05:16:46PM -0800, Emily Shaffer wrote:
> Teach 'git grep' how to receive pathspecs via file, and add convenience
> flags for receiving pathspecs or patterns via stdin.
> 
> In some cases, the list of pathspecs to 'git grep' is longer than the
> command line allows, or long enough that a user becomes fatigued reading
> the command.  In other cases, a user may wish to write a script or
> oneliner which generates a list of files to 'git grep' against. In both
> scenarios, a reasonable workaround is to provide the list of pathspecs
> via a file or stdin.
> 
> Before this change, it was already possible to receive patterns via
> stdin by using the argument '-f -'. Now that there are two arguments
> which could both use stdin, help safeguard the user from doing so by
> providing convenience '--stdin-patterns' and '--stdin-pathspecs' which
> are mutually exclusive.  (It is still possible to ask for '-f -
> --pathspecs-file -', though.)
> 
> Finally, in order to match '--pathspecs-file', give '-f' a long form
> '--patterns-file' too.
> 
> Signed-off-by: Emily Shaffer <[email-masked]>
> ---
> Providing too many pathspecs for the argument list to handle is causing
> some gore out in the wild with git-secrets:
> https://github.com/awslabs/git-secrets/issues/78

Out of curiosity, are there any situations that --pathspecs-file handles
better than an xargs invocation? I didn't take a look at the code of
git-secrets but I suspect that that could solve their problem.

The reason I ask is because (correct me if I'm wrong) a lot of other git
commands (like add, reset and checkout) don't seem to accept pathspecs
via stdin and could suffer the same problem. xargs seems like a more
general way of solving the problem of long command lines.

> 
> A short arg for --pathspecs-file didn't occur to me because grep has
> many short args already, but if anyone has a suggestion I'll happily add
> it.
> 
> The pathspec list is gathered into an argv_array because parse_pathspec
> is only called once, against the entire list of pathspecs. Perhaps it
> makes sense to concatenate the paths given on the command line with the
> paths given via file, but since it was nontrivial to merge two
> argv_arrays and I wasn't certain it was the right choice, I didn't do
> so. I'd probably implement that by adding a utility function to
> argv-array. ('-f somepatterns.txt -e otherpattern' concatenates the
> patterns, by the way.)
> 
>  - Emily
> 
>  Documentation/git-grep.txt | 18 ++++++++++-
>  builtin/grep.c             | 61 +++++++++++++++++++++++++++++++++-----
>  t/t7810-grep.sh            | 52 ++++++++++++++++++++++++++++++--
>  3 files changed, 121 insertions(+), 10 deletions(-)
> 
> diff --git a/Documentation/git-grep.txt b/Documentation/git-grep.txt
> index c89fb569e3..fb588a3846 100644
> --- a/Documentation/git-grep.txt
> +++ b/Documentation/git-grep.txt
> @@ -24,7 +24,8 @@ SYNOPSIS
>  	   [-A <post-context>] [-B <pre-context>] [-C <context>]
>  	   [-W | --function-context]
>  	   [--threads <num>]
> -	   [-f <file>] [-e] <pattern>
> +	   [--pathspecs-file <file>] [--stdin-pathspecs]
> +	   [-f | --patterns-file <file>] [--stdin-patterns] [-e] <pattern>
>  	   [--and|--or|--not|(|)|-e <pattern>...]
>  	   [--recurse-submodules] [--parent-basename <basename>]
>  	   [ [--[no-]exclude-standard] [--cached | --no-index | --untracked] | <tree>...]
> @@ -270,7 +271,22 @@ providing this option will cause it to die.
>  	See `grep.threads` in 'CONFIGURATION' for more information.
>  
>  -f <file>::
> +--patterns-file <file>::
>  	Read patterns from <file>, one per line.
> +
> +--stdin-patterns::
> +	Read patterns from stdin, one per line. Equivalent to `-f -`. Cannot be
> +	combined with `--stdin-pathspecs`.
> +
> +--pathspecs-file <file>::
> +	Read pathspecs from <file>, one per line. Pathspecs passed in the
> +	argument list will be ignored in this mode.
> +
> +--stdin-pathspecs::
> +	Read pathspecs from stdin, one per line. Pathspecs passed in the
> +	argument list will be ignored in this mode. Equivalent to
> +	`--pathspecs-file -`.
> +
>  +
>  Passing the pattern via <file> allows for providing a search pattern
>  containing a \0.
> diff --git a/builtin/grep.c b/builtin/grep.c
> index 50ce8d9461..f6f9f84002 100644
> --- a/builtin/grep.c
> +++ b/builtin/grep.c
> @@ -720,16 +720,38 @@ static int context_callback(const struct option *opt, const char *arg,
>  	return 0;
>  }
>  
> -static int file_callback(const struct option *opt, const char *arg, int unset)
> +static int pathspec_file(struct argv_array *pathspec_argv, const char *arg)
> +{
> +	struct strbuf sb = STRBUF_INIT;
> +
> +	if (!strcmp(arg, "-")) {
> +		while (strbuf_getline(&sb, stdin) != EOF)
> +			argv_array_push(pathspec_argv, sb.buf);
> +	}
> +	else {
> +		if (!strbuf_read_file(&sb, arg, 0))
> +			die_errno(_("cannot open '%s'"), arg);
> +		argv_array_split(pathspec_argv, sb.buf);
> +	}
> +
> +	strbuf_release(&sb);
> +	return 0;
> +}
> +
> +static int pathspec_file_callback(const struct option *opt,
> +				  const char *arg, int unset)
> +{
> +	BUG_ON_OPT_NEG(unset);
> +	return pathspec_file(opt->value, arg);
> +}
> +
> +static int pattern_file(struct grep_opt *grep_opt, const char *arg)
>  {
> -	struct grep_opt *grep_opt = opt->value;
>  	int from_stdin;
>  	FILE *patterns;
>  	int lno = 0;
>  	struct strbuf sb = STRBUF_INIT;
>  
> -	BUG_ON_OPT_NEG(unset);
> -
>  	from_stdin = !strcmp(arg, "-");
>  	patterns = from_stdin ? stdin : fopen(arg, "r");
>  	if (!patterns)
> @@ -748,6 +770,12 @@ static int file_callback(const struct option *opt, const char *arg, int unset)
>  	return 0;
>  }
>  
> +static int pattern_file_callback(const struct option *opt, const char *arg, int unset)
> +{
> +	BUG_ON_OPT_NEG(unset);
> +	return pattern_file(opt->value, arg);
> +}
> +
>  static int not_callback(const struct option *opt, const char *arg, int unset)
>  {
>  	struct grep_opt *grep_opt = opt->value;
> @@ -803,12 +831,15 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
>  	struct grep_opt opt;
>  	struct object_array list = OBJECT_ARRAY_INIT;
>  	struct pathspec pathspec;
> +	struct argv_array pathspec_argv;
>  	struct string_list path_list = STRING_LIST_INIT_NODUP;
>  	int i;
>  	int dummy;
>  	int use_index = 1;
>  	int pattern_type_arg = GREP_PATTERN_TYPE_UNSPECIFIED;
>  	int allow_revs;
> +	int stdin_patterns = 0;
> +	int stdin_pathspecs = 0;
>  
>  	struct option options[] = {
>  		OPT_BOOL(0, "cached", &cached,
> @@ -896,8 +927,14 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
>  		OPT_BOOL('W', "function-context", &opt.funcbody,
>  			N_("show the surrounding function")),
>  		OPT_GROUP(""),
> -		OPT_CALLBACK('f', NULL, &opt, N_("file"),
> -			N_("read patterns from file"), file_callback),
> +		OPT_CALLBACK('f', "patterns-file", &opt, N_("file"),
> +			N_("read patterns from file"), pattern_file_callback),
> +		OPT_BOOL(0, "stdin-patterns", &stdin_patterns,
> +			 N_("read patterns from stdin")),
> +		OPT_CALLBACK(0, "pathspecs-file", &pathspec_argv, N_("file"),
> +			N_("read pathspecs from file"), pathspec_file_callback),
> +		OPT_BOOL(0, "stdin-pathspecs", &stdin_pathspecs,
> +			 N_("read pathspecs from stdin")),
>  		{ OPTION_CALLBACK, 'e', NULL, &opt, N_("pattern"),
>  			N_("match <pattern>"), PARSE_OPT_NONEG, pattern_callback },
>  		{ OPTION_CALLBACK, 0, "and", &opt, NULL,
> @@ -949,6 +986,15 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
>  			     PARSE_OPT_STOP_AT_NON_OPTION);
>  	grep_commit_pattern_type(pattern_type_arg, &opt);
>  
> +	if (stdin_patterns && stdin_pathspecs)
> +		die(_("cannot use stdin for both patterns and pathspecs"));
> +
> +	if (stdin_patterns)
> +		pattern_file(&opt, "-");
> +
> +	if (stdin_pathspecs)
> +		pathspec_file(&pathspec_argv, "-");
> +
>  	if (use_index && !startup_info->have_repository) {
>  		int fallback = 0;
>  		git_config_get_bool("grep.fallbacktonoindex", &fallback);
> @@ -1057,7 +1103,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
>  	parse_pathspec(&pathspec, 0,
>  		       PATHSPEC_PREFER_CWD |
>  		       (opt.max_depth != -1 ? PATHSPEC_MAXDEPTH_VALID : 0),
> -		       prefix, argv + i);
> +		       prefix,
> +		       (pathspec_argv.argc ? pathspec_argv.argv : argv) + i);
>  	pathspec.max_depth = opt.max_depth;
>  	pathspec.recursive = 1;
>  	pathspec.recurse_submodules = !!recurse_submodules;
> diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
> index 7d7b396c23..be8e60cfa0 100755
> --- a/t/t7810-grep.sh
> +++ b/t/t7810-grep.sh
> @@ -549,6 +549,10 @@ test_expect_success 'grep -f, non-existent file' '
>  	test_must_fail git grep -f patterns
>  '
>  
> +text_expect_success 'grep --pathspec-file, non-existent file' '
> +	test_must_fail git grep --pathspecs-file pathspecs
> +'
> +
>  cat >expected <<EOF
>  file:foo mmap bar
>  file:foo_mmap bar
> @@ -582,8 +586,8 @@ mmap
>  vvv
>  EOF
>  
> -test_expect_success 'grep -f, multiple patterns' '
> -	git grep -f patterns >actual &&
> +test_expect_success 'grep --patterns-file, multiple patterns' '
> +	git grep --patterns-file patterns >actual &&
>  	test_cmp expected actual
>  '
>  
> @@ -621,6 +625,11 @@ test_expect_success 'grep -f, ignore empty lines, read patterns from stdin' '
>  	test_cmp expected actual
>  '
>  
> +test_expect_success 'grep --stdin--patterns' '
> +	git grep --stdin-patterns <patterns >actual &&
> +	test_cmp expected actual
> +'
> +
>  cat >expected <<EOF
>  y:y yy
>  --
> @@ -1125,6 +1134,45 @@ test_expect_success 'grep --no-index descends into repos, but not .git' '
>  	)
>  '
>  
> +test_expect_success 'setup pathspecs-file tests' '
> +cat >excluded-file <<EOF &&
> +bar
> +EOF
> +cat >pathspec-file <<EOF &&
> +foo
> +bar
> +baz
> +EOF
> +cat >unrelated-file <<EOF &&
> +xyz
> +EOF
> +git add excluded-file pathspec-file unrelated-file
> +'

Please indent these commands in and use `-\EOF` for the here-doc.

> +
> +cat >pathspecs <<EOF
> +pathspec-file
> +unrelated-file
> +EOF
> +
> +cat >expected <<EOF
> +pathspec-file:bar
> +EOF

Is there any reason why these two aren't part of the setup above?

Also, even though 'expect' is the conventional name for the expected
output file, it seems like the rest of the test uses 'expected' so I
guess it's fine to leave it as is.

Thanks,

Denton

> +
> +test_expect_success 'grep --stdin-pathspecs' '
> +	git grep --stdin-pathspecs "bar" <pathspecs >actual &&
> +	test_cmp expected actual
> +'
> +
> +test_expect_success 'grep --pathspecs-file with file' '
> +	git grep --pathspecs-file pathspecs "bar" >actual &&
> +	test_cmp expected actual
> +'
> +
> +test_expect_success 'grep --pathspec-file with stdin' '
> +	git grep --pathspecs-file - "bar" <pathspecs >actual &&
> +	test_cmp expected actual
> +'
> +
>  test_expect_success 'setup double-dash tests' '
>  cat >double-dash <<EOF &&
>  --
> -- 
> 2.24.0.432.g9d3f5f5b63-goog
>