grep: fix bug when recursing with relative pathspec

When using the --recurse-submodules flag with a relative pathspec which
includes "..", an error is produced inside the child process spawned for
a submodule.  When creating the pathspec struct in the child, the ".."
is interpreted to mean "go up a directory" which causes an error stating
that the path ".." is outside of the repository.

While it is true that ".." is outside the scope of the submodule, it is
confusing to a user who originally invoked the command where ".." was
indeed still inside the scope of the superproject.  Since the child
process launched for the submodule has some context that it is operating
underneath a superproject, this error could be avoided.

This patch fixes the bug by passing the 'prefix' to the child process.
Now each child process that works on a submodule has two points of
reference to the superproject: (1) the 'super_prefix' which is the path
from the root of the superproject down to root of the submodule and (2)
the 'prefix' which is the path from the root of the superproject down to
the directory where the user invoked the git command.

With these two pieces of information a child process can correctly
interpret the pathspecs provided by the user as well as being able to
properly format its output relative to the directory the user invoked
the original command from.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/grep.c

@@ -310,10 +310,7 @@ static int grep_sha1(struct grep_opt *opt, const unsigned char *sha1,
 {
 	struct strbuf pathbuf = STRBUF_INIT;
 
-	if (opt->relative && opt->prefix_length) {
-		quote_path_relative(filename + tree_name_len, opt->prefix, &pathbuf);
-		strbuf_insert(&pathbuf, 0, filename, tree_name_len);
-	} else if (super_prefix) {
+	if (super_prefix) {
 		strbuf_add(&pathbuf, filename, tree_name_len);
 		strbuf_addstr(&pathbuf, super_prefix);
 		strbuf_addstr(&pathbuf, filename + tree_name_len);
@@ -321,6 +318,13 @@ static int grep_sha1(struct grep_opt *opt, const unsigned char *sha1,
 		strbuf_addstr(&pathbuf, filename);
 	}
 
+	if (opt->relative && opt->prefix_length) {
+		char *name = strbuf_detach(&pathbuf, NULL);
+		quote_path_relative(name + tree_name_len, opt->prefix, &pathbuf);
+		strbuf_insert(&pathbuf, 0, name, tree_name_len);
+		free(name);
+	}
+
 #ifndef NO_PTHREADS
 	if (num_threads) {
 		add_work(opt, GREP_SOURCE_SHA1, pathbuf.buf, path, sha1);
@@ -345,12 +349,14 @@ static int grep_file(struct grep_opt *opt, const char *filename)
 {
 	struct strbuf buf = STRBUF_INIT;
 
+	if (super_prefix)
+		strbuf_addstr(&buf, super_prefix);
+	strbuf_addstr(&buf, filename);
+
 	if (opt->relative && opt->prefix_length) {
-		quote_path_relative(filename, opt->prefix, &buf);
-	} else {
-		if (super_prefix)
-			strbuf_addstr(&buf, super_prefix);
-		strbuf_addstr(&buf, filename);
+		char *name = strbuf_detach(&buf, NULL);
+		quote_path_relative(name, opt->prefix, &buf);
+		free(name);
 	}
 
 #ifndef NO_PTHREADS
@@ -399,13 +405,12 @@ static void run_pager(struct grep_opt *opt, const char *prefix)
 }
 
 static void compile_submodule_options(const struct grep_opt *opt,
-				      const struct pathspec *pathspec,
+				      const char **argv,
 				      int cached, int untracked,
 				      int opt_exclude, int use_index,
 				      int pattern_type_arg)
 {
 	struct grep_pat *pattern;
-	int i;
 
 	if (recurse_submodules)
 		argv_array_push(&submodule_options, "--recurse-submodules");
@@ -523,9 +528,8 @@ static void compile_submodule_options(const struct grep_opt *opt,
 
 	/* Add Pathspecs */
 	argv_array_push(&submodule_options, "--");
-	for (i = 0; i < pathspec->nr; i++)
-		argv_array_push(&submodule_options,
-				pathspec->items[i].original);
+	for (; *argv; argv++)
+		argv_array_push(&submodule_options, *argv);
 }
 
 /*
@@ -549,6 +553,11 @@ static int grep_submodule_launch(struct grep_opt *opt,
 	prepare_submodule_repo_env(&cp.env_array);
 	argv_array_push(&cp.env_array, GIT_DIR_ENVIRONMENT);
 
+	if (opt->relative && opt->prefix_length)
+		argv_array_pushf(&cp.env_array, "%s=%s",
+				 GIT_TOPLEVEL_PREFIX_ENVIRONMENT,
+				 opt->prefix);
+
 	/* Add super prefix */
 	argv_array_pushf(&cp.args, "--super-prefix=%s%s/",
 			 super_prefix ? super_prefix : "",
@@ -1206,7 +1215,7 @@ int cmd_grep(int argc, const char **argv, const char *prefix)
 
 	if (recurse_submodules) {
 		gitmodules_config();
-		compile_submodule_options(&opt, &pathspec, cached, untracked,
+		compile_submodule_options(&opt, argv + i, cached, untracked,
 					  opt_exclude, use_index,
 					  pattern_type_arg);
 	}

t/t7814-grep-recurse-submodules.sh

@@ -227,6 +227,81 @@ test_expect_success 'grep history with moved submoules' '
 	test_cmp expect actual
 '
 
+test_expect_success 'grep using relative path' '
+	test_when_finished "rm -rf parent sub" &&
+	git init sub &&
+	echo "foobar" >sub/file &&
+	git -C sub add file &&
+	git -C sub commit -m "add file" &&
+
+	git init parent &&
+	echo "foobar" >parent/file &&
+	git -C parent add file &&
+	mkdir parent/src &&
+	echo "foobar" >parent/src/file2 &&
+	git -C parent add src/file2 &&
+	git -C parent submodule add ../sub &&
+	git -C parent commit -m "add files and submodule" &&
+
+	# From top works
+	cat >expect <<-\EOF &&
+	file:foobar
+	src/file2:foobar
+	sub/file:foobar
+	EOF
+	git -C parent grep --recurse-submodules -e "foobar" >actual &&
+	test_cmp expect actual &&
+
+	# Relative path to top
+	cat >expect <<-\EOF &&
+	../file:foobar
+	file2:foobar
+	../sub/file:foobar
+	EOF
+	git -C parent/src grep --recurse-submodules -e "foobar" -- .. >actual &&
+	test_cmp expect actual &&
+
+	# Relative path to submodule
+	cat >expect <<-\EOF &&
+	../sub/file:foobar
+	EOF
+	git -C parent/src grep --recurse-submodules -e "foobar" -- ../sub >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'grep from a subdir' '
+	test_when_finished "rm -rf parent sub" &&
+	git init sub &&
+	echo "foobar" >sub/file &&
+	git -C sub add file &&
+	git -C sub commit -m "add file" &&
+
+	git init parent &&
+	mkdir parent/src &&
+	echo "foobar" >parent/src/file &&
+	git -C parent add src/file &&
+	git -C parent submodule add ../sub src/sub &&
+	git -C parent submodule add ../sub sub &&
+	git -C parent commit -m "add files and submodules" &&
+
+	# Verify grep from root works
+	cat >expect <<-\EOF &&
+	src/file:foobar
+	src/sub/file:foobar
+	sub/file:foobar
+	EOF
+	git -C parent grep --recurse-submodules -e "foobar" >actual &&
+	test_cmp expect actual &&
+
+	# Verify grep from a subdir works
+	cat >expect <<-\EOF &&
+	file:foobar
+	sub/file:foobar
+	EOF
+	git -C parent/src grep --recurse-submodules -e "foobar" >actual &&
+	test_cmp expect actual
+'
+
 test_incompatible_with_recurse_submodules ()
 {
 	test_expect_success "--recurse-submodules and $1 are incompatible" "