Resurrect "git grep --no-index"

This reverts commit 3c8f6c8 (Revert 30816237 and 7e62265, 2010-02-05) as
the issue has been sorted out.

builtin-grep.c

@@ -14,6 +14,7 @@
 #include "userdiff.h"
 #include "grep.h"
 #include "quote.h"
+#include "dir.h"
 
 #ifndef NO_PTHREADS
 #include "thread-utils.h"
@@ -645,6 +646,24 @@ static int grep_object(struct grep_opt *opt, const char **paths,
 	die("unable to grep from object of type %s", typename(obj->type));
 }
 
+static int grep_directory(struct grep_opt *opt, const char **paths)
+{
+	struct dir_struct dir;
+	int i, hit = 0;
+
+	memset(&dir, 0, sizeof(dir));
+	setup_standard_excludes(&dir);
+
+	fill_directory(&dir, paths);
+	for (i = 0; i < dir.nr; i++) {
+		hit |= grep_file(opt, dir.entries[i]->name);
+		if (hit && opt->status_only)
+			break;
+	}
+	free_grep_patterns(opt);
+	return hit;
+}
+
 static int context_callback(const struct option *opt, const char *arg,
 			    int unset)
 {
@@ -739,9 +758,12 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 	const char **paths = NULL;
 	int i;
 	int dummy;
+	int nongit = 0, use_index = 1;
 	struct option options[] = {
 		OPT_BOOLEAN(0, "cached", &cached,
 			"search in index instead of in the work tree"),
+		OPT_BOOLEAN(0, "index", &use_index,
+			"--no-index finds in contents not managed by git"),
 		OPT_GROUP(""),
 		OPT_BOOLEAN('v', "invert-match", &opt.invert,
 			"show non-matching lines"),
@@ -824,6 +846,8 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		OPT_END()
 	};
 
+	prefix = setup_git_directory_gently(&nongit);
+
 	/*
 	 * 'git grep -h', unlike 'git grep -h <pattern>', is a request
 	 * to show usage information and exit.
@@ -861,6 +885,10 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 			     PARSE_OPT_STOP_AT_NON_OPTION |
 			     PARSE_OPT_NO_INTERNAL_HELP);
 
+	if (use_index && nongit)
+		/* die the same way as if we did it at the beginning */
+		setup_git_directory();
+
 	/* First unrecognized non-option token */
 	if (argc > 0 && !opt.pattern_list) {
 		append_grep_pattern(&opt, argv[0], "command line", 0,
@@ -922,6 +950,18 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 		paths[1] = NULL;
 	}
 
+	if (!use_index) {
+		int hit;
+		if (cached)
+			die("--cached cannot be used with --no-index.");
+		if (list.nr)
+			die("--no-index cannot be used with revs.");
+		hit = grep_directory(&opt, paths);
+		if (use_threads)
+			hit |= wait_all();
+		return !hit;
+	}
+
 	if (!list.nr) {
 		int hit;
 		if (!cached)

git.c

@@ -317,7 +317,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "fsck-objects", cmd_fsck, RUN_SETUP },
 		{ "gc", cmd_gc, RUN_SETUP },
 		{ "get-tar-commit-id", cmd_get_tar_commit_id },
-		{ "grep", cmd_grep, RUN_SETUP | USE_PAGER },
+		{ "grep", cmd_grep, USE_PAGER },
 		{ "hash-object", cmd_hash_object },
 		{ "help", cmd_help },
 		{ "index-pack", cmd_index_pack },

t/t7002-grep.sh

@@ -434,4 +434,56 @@ test_expect_success 'grep -Fi' '
 	test_cmp expected actual
 '
 
+test_expect_success 'outside of git repository' '
+	rm -fr non &&
+	mkdir -p non/git/sub &&
+	echo hello >non/git/file1 &&
+	echo world >non/git/sub/file2 &&
+	echo ".*o*" >non/git/.gitignore &&
+	{
+		echo file1:hello &&
+		echo sub/file2:world
+	} >non/expect.full &&
+	echo file2:world >non/expect.sub
+	(
+		GIT_CEILING_DIRECTORIES="$(pwd)/non/git" &&
+		export GIT_CEILING_DIRECTORIES &&
+		cd non/git &&
+		test_must_fail git grep o &&
+		git grep --no-index o >../actual.full &&
+		test_cmp ../expect.full ../actual.full
+		cd sub &&
+		test_must_fail git grep o &&
+		git grep --no-index o >../../actual.sub &&
+		test_cmp ../../expect.sub ../../actual.sub
+	)
+'
+
+test_expect_success 'inside git repository but with --no-index' '
+	rm -fr is &&
+	mkdir -p is/git/sub &&
+	echo hello >is/git/file1 &&
+	echo world >is/git/sub/file2 &&
+	echo ".*o*" >is/git/.gitignore &&
+	{
+		echo file1:hello &&
+		echo sub/file2:world
+	} >is/expect.full &&
+	: >is/expect.empty &&
+	echo file2:world >is/expect.sub
+	(
+		cd is/git &&
+		git init &&
+		test_must_fail git grep o >../actual.full &&
+		test_cmp ../expect.empty ../actual.full &&
+		git grep --no-index o >../actual.full &&
+		test_cmp ../expect.full ../actual.full &&
+		cd sub &&
+		test_must_fail git grep o >../../actual.sub &&
+		test_cmp ../../expect.empty ../../actual.sub &&
+		git grep --no-index o >../../actual.sub &&
+		test_cmp ../../expect.sub ../../actual.sub
+	)
+'
+
 test_done