grep: prepare to run outside of a work tree

This moves the call to setup_git_directory() for running "grep" from
the "git" wrapper to the implementation of the "grep" subcommand.  A
new variable "use_index" is always true at this stage in the series,
and when it is on, we require that we are in a directory that is under
git control.  To make sure we die the same way, we make a second call
into setup_git_directory() when we detect this situation.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-grep.c

@@ -414,6 +414,7 @@ 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"),
@@ -497,6 +498,8 @@ 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.
@@ -534,6 +537,10 @@ 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,

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 },
 		{ "help", cmd_help },
 		{ "init", cmd_init_db },
 		{ "init-db", cmd_init_db },