Merge branch 'jn/maint-setup-fix' (early part) into jn/paginate-fix

* 'jn/maint-setup-fix' (early part):
  Revert "rehabilitate 'git index-pack' inside the object store"
  setup: do not forget working dir from subdir of gitdir
  t4111 (apply): refresh index before applying patches to it
  setup: split off get_device_or_die helper
  setup: split off a function to handle hitting ceiling in repo search
  setup: split off code to handle stumbling upon a repository
  setup: split off a function to checks working dir for .git file
  setup: split off $GIT_DIR-set case from setup_git_directory_gently
  tests: try git apply from subdir of toplevel
  t1501 (rev-parse): clarify

4 files changed, 556 insertions, 264 deletions

diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index a89ae831dd..89a1f12d61 100644
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -880,29 +880,15 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 	char *index_name_buf = NULL, *keep_name_buf = NULL;
 	struct pack_idx_entry **idx_objects;
 	unsigned char pack_sha1[20];
+	int nongit;
 
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage(index_pack_usage);
 
-	/*
-	 * We wish to read the repository's config file if any, and
-	 * for that it is necessary to call setup_git_directory_gently().
-	 * However if the cwd was inside .git/objects/pack/ then we need
-	 * to go back there or all the pack name arguments will be wrong.
-	 * And in that case we cannot rely on any prefix returned by
-	 * setup_git_directory_gently() either.
-	 */
-	{
-		char cwd[PATH_MAX+1];
-		int nongit;
-
-		if (!getcwd(cwd, sizeof(cwd)-1))
-			die("Unable to get current working directory");
-		setup_git_directory_gently(&nongit);
-		git_config(git_index_pack_config, NULL);
-		if (chdir(cwd))
-			die("Cannot come back to cwd");
-	}
+	prefix = setup_git_directory_gently(&nongit);
+	git_config(git_index_pack_config, NULL);
+	if (prefix && chdir(prefix))
+		die("Cannot come back to cwd");
 
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
diff --git a/setup.c b/setup.c
index 28a2b69d05..6ee1e28bd8 100644
--- a/setup.c
+++ b/setup.c
@@ -313,6 +313,93 @@ const char *read_gitfile_gently(const char *path)
 	return path;
 }
 
+static const char *setup_explicit_git_dir(const char *gitdirenv,
+				const char *work_tree_env, int *nongit_ok)
+{
+	static char buffer[1024 + 1];
+	const char *retval;
+
+	if (PATH_MAX - 40 < strlen(gitdirenv))
+		die("'$%s' too big", GIT_DIR_ENVIRONMENT);
+	if (!is_git_directory(gitdirenv)) {
+		if (nongit_ok) {
+			*nongit_ok = 1;
+			return NULL;
+		}
+		die("Not a git repository: '%s'", gitdirenv);
+	}
+	if (!work_tree_env) {
+		retval = set_work_tree(gitdirenv);
+		/* config may override worktree */
+		if (check_repository_format_gently(nongit_ok))
+			return NULL;
+		return retval;
+	}
+	if (check_repository_format_gently(nongit_ok))
+		return NULL;
+	retval = get_relative_cwd(buffer, sizeof(buffer) - 1,
+			get_git_work_tree());
+	if (!retval || !*retval)
+		return NULL;
+	set_git_dir(make_absolute_path(gitdirenv));
+	if (chdir(work_tree_env) < 0)
+		die_errno ("Could not chdir to '%s'", work_tree_env);
+	strcat(buffer, "/");
+	return retval;
+}
+
+static int cwd_contains_git_dir(const char **gitfile_dirp)
+{
+	const char *gitfile_dir = read_gitfile_gently(DEFAULT_GIT_DIR_ENVIRONMENT);
+	*gitfile_dirp = gitfile_dir;
+	if (gitfile_dir) {
+		if (set_git_dir(gitfile_dir))
+			die("Repository setup failed");
+		return 1;
+	}
+	return is_git_directory(DEFAULT_GIT_DIR_ENVIRONMENT);
+}
+
+static const char *setup_bare_git_dir(const char *work_tree_env,
+		int offset, int len, char *cwd, int *nongit_ok)
+{
+	int root_len;
+
+	inside_git_dir = 1;
+	if (!work_tree_env)
+		inside_work_tree = 0;
+	if (offset != len) {
+		if (chdir(cwd))
+			die_errno("Cannot come back to cwd");
+		root_len = offset_1st_component(cwd);
+		cwd[offset > root_len ? offset : root_len] = '\0';
+		set_git_dir(cwd);
+	} else
+		set_git_dir(".");
+	check_repository_format_gently(nongit_ok);
+	return NULL;
+}
+
+static const char *setup_nongit(const char *cwd, int *nongit_ok)
+{
+	if (!nongit_ok)
+		die("Not a git repository (or any of the parent directories): %s", DEFAULT_GIT_DIR_ENVIRONMENT);
+	if (chdir(cwd))
+		die_errno("Cannot come back to cwd");
+	*nongit_ok = 1;
+	return NULL;
+}
+
+static dev_t get_device_or_die(const char *path, const char *prefix)
+{
+	struct stat buf;
+	if (stat(path, &buf))
+		die_errno("failed to stat '%s%s%s'",
+				prefix ? prefix : "",
+				prefix ? "/" : "", path);
+	return buf.st_dev;
+}
+
 /*
  * We cannot decide in this function whether we are in the work tree or
  * not, since the config can only be read _after_ this function was called.
@@ -327,7 +414,6 @@ static const char *setup_git_directory_gently_1(int *nongit_ok)
 	int len, offset, ceil_offset, root_len;
 	dev_t current_device = 0;
 	int one_filesystem = 1;
-	struct stat buf;
 
 	/*
 	 * Let's assume that we are in a git repository.
@@ -343,38 +429,8 @@ static const char *setup_git_directory_gently_1(int *nongit_ok)
 	 * validation.
 	 */
 	gitdirenv = getenv(GIT_DIR_ENVIRONMENT);
-	if (gitdirenv) {
-		if (PATH_MAX - 40 < strlen(gitdirenv))
-			die("'$%s' too big", GIT_DIR_ENVIRONMENT);
-		if (is_git_directory(gitdirenv)) {
-			static char buffer[1024 + 1];
-			const char *retval;
-
-			if (!work_tree_env) {
-				retval = set_work_tree(gitdirenv);
-				/* config may override worktree */
-				if (check_repository_format_gently(nongit_ok))
-					return NULL;
-				return retval;
-			}
-			if (check_repository_format_gently(nongit_ok))
-				return NULL;
-			retval = get_relative_cwd(buffer, sizeof(buffer) - 1,
-					get_git_work_tree());
-			if (!retval || !*retval)
-				return NULL;
-			set_git_dir(make_absolute_path(gitdirenv));
-			if (chdir(work_tree_env) < 0)
-				die_errno ("Could not chdir to '%s'", work_tree_env);
-			strcat(buffer, "/");
-			return retval;
-		}
-		if (nongit_ok) {
-			*nongit_ok = 1;
-			return NULL;
-		}
-		die("Not a git repository: '%s'", gitdirenv);
-	}
+	if (gitdirenv)
+		return setup_explicit_git_dir(gitdirenv, work_tree_env, nongit_ok);
 
 	if (!getcwd(cwd, sizeof(cwd)-1))
 		die_errno("Unable to read current working directory");
@@ -396,49 +452,20 @@ static const char *setup_git_directory_gently_1(int *nongit_ok)
 	 */
 	offset = len = strlen(cwd);
 	one_filesystem = !git_env_bool("GIT_DISCOVERY_ACROSS_FILESYSTEM", 0);
-	if (one_filesystem) {
-		if (stat(".", &buf))
-			die_errno("failed to stat '.'");
-		current_device = buf.st_dev;
-	}
+	if (one_filesystem)
+		current_device = get_device_or_die(".", NULL);
 	for (;;) {
-		gitfile_dir = read_gitfile_gently(DEFAULT_GIT_DIR_ENVIRONMENT);
-		if (gitfile_dir) {
-			if (set_git_dir(gitfile_dir))
-				die("Repository setup failed");
-			break;
-		}
-		if (is_git_directory(DEFAULT_GIT_DIR_ENVIRONMENT))
+		if (cwd_contains_git_dir(&gitfile_dir))
 			break;
-		if (is_git_directory(".")) {
-			inside_git_dir = 1;
-			if (!work_tree_env)
-				inside_work_tree = 0;
-			if (offset != len) {
-				root_len = offset_1st_component(cwd);
-				cwd[offset > root_len ? offset : root_len] = '\0';
-				set_git_dir(cwd);
-			} else
-				set_git_dir(".");
-			check_repository_format_gently(nongit_ok);
-			return NULL;
-		}
+		if (is_git_directory("."))
+			return setup_bare_git_dir(work_tree_env, offset,
+							len, cwd, nongit_ok);
 		while (--offset > ceil_offset && cwd[offset] != '/');
-		if (offset <= ceil_offset) {
-			if (nongit_ok) {
-				if (chdir(cwd))
-					die_errno("Cannot come back to cwd");
-				*nongit_ok = 1;
-				return NULL;
-			}
-			die("Not a git repository (or any of the parent directories): %s", DEFAULT_GIT_DIR_ENVIRONMENT);
-		}
+		if (offset <= ceil_offset)
+			return setup_nongit(cwd, nongit_ok);
 		if (one_filesystem) {
-			if (stat("..", &buf)) {
-				cwd[offset] = '\0';
-				die_errno("failed to stat '%s/..'", cwd);
-			}
-			if (buf.st_dev != current_device) {
+			dev_t parent_device = get_device_or_die("..", cwd);
+			if (parent_device != current_device) {
 				if (nongit_ok) {
 					if (chdir(cwd))
 						die_errno("Cannot come back to cwd");
diff --git a/t/t1501-worktree.sh b/t/t1501-worktree.sh
index bd8b60732b..2c8f01f668 100755
--- a/t/t1501-worktree.sh
+++ b/t/t1501-worktree.sh
@@ -3,183 +3,320 @@
 test_description='test separate work tree'
 . ./test-lib.sh
 
-test_rev_parse() {
-	name=$1
-	shift
-
-	test_expect_success "$name: is-bare-repository" \
-	"test '$1' = \"\$(git rev-parse --is-bare-repository)\""
-	shift
-	[ $# -eq 0 ] && return
-
-	test_expect_success "$name: is-inside-git-dir" \
-	"test '$1' = \"\$(git rev-parse --is-inside-git-dir)\""
-	shift
-	[ $# -eq 0 ] && return
-
-	test_expect_success "$name: is-inside-work-tree" \
-	"test '$1' = \"\$(git rev-parse --is-inside-work-tree)\""
-	shift
-	[ $# -eq 0 ] && return
-
-	test_expect_success "$name: prefix" \
-	"test '$1' = \"\$(git rev-parse --show-prefix)\""
-	shift
-	[ $# -eq 0 ] && return
-}
-
-EMPTY_TREE=$(git write-tree)
-mkdir -p work/sub/dir || exit 1
-mkdir -p work2 || exit 1
-mv .git repo.git || exit 1
-
-say "core.worktree = relative path"
-GIT_DIR=repo.git
-GIT_CONFIG="$(pwd)"/$GIT_DIR/config
-export GIT_DIR GIT_CONFIG
-unset GIT_WORK_TREE
-git config core.worktree ../work
-test_rev_parse 'outside'      false false false
-cd work || exit 1
-GIT_DIR=../repo.git
-GIT_CONFIG="$(pwd)"/$GIT_DIR/config
-test_rev_parse 'inside'       false false true ''
-cd sub/dir || exit 1
-GIT_DIR=../../../repo.git
-GIT_CONFIG="$(pwd)"/$GIT_DIR/config
-test_rev_parse 'subdirectory' false false true sub/dir/
-cd ../../.. || exit 1
-
-say "core.worktree = absolute path"
-GIT_DIR=$(pwd)/repo.git
-GIT_CONFIG=$GIT_DIR/config
-git config core.worktree "$(pwd)/work"
-test_rev_parse 'outside'      false false false
-cd work2
-test_rev_parse 'outside2'     false false false
-cd ../work || exit 1
-test_rev_parse 'inside'       false false true ''
-cd sub/dir || exit 1
-test_rev_parse 'subdirectory' false false true sub/dir/
-cd ../../.. || exit 1
-
-say "GIT_WORK_TREE=relative path (override core.worktree)"
-GIT_DIR=$(pwd)/repo.git
-GIT_CONFIG=$GIT_DIR/config
-git config core.worktree non-existent
-GIT_WORK_TREE=work
-export GIT_WORK_TREE
-test_rev_parse 'outside'      false false false
-cd work2
-test_rev_parse 'outside'      false false false
-cd ../work || exit 1
-GIT_WORK_TREE=.
-test_rev_parse 'inside'       false false true ''
-cd sub/dir || exit 1
-GIT_WORK_TREE=../..
-test_rev_parse 'subdirectory' false false true sub/dir/
-cd ../../.. || exit 1
-
-mv work repo.git/work
-mv work2 repo.git/work2
-
-say "GIT_WORK_TREE=absolute path, work tree below git dir"
-GIT_DIR=$(pwd)/repo.git
-GIT_CONFIG=$GIT_DIR/config
-GIT_WORK_TREE=$(pwd)/repo.git/work
-test_rev_parse 'outside'              false false false
-cd repo.git || exit 1
-test_rev_parse 'in repo.git'              false true  false
-cd objects || exit 1
-test_rev_parse 'in repo.git/objects'      false true  false
-cd ../work2 || exit 1
-test_rev_parse 'in repo.git/work2'      false true  false
-cd ../work || exit 1
-test_rev_parse 'in repo.git/work'         false true true ''
-cd sub/dir || exit 1
-test_rev_parse 'in repo.git/sub/dir' false true true sub/dir/
-cd ../../../.. || exit 1
-
-test_expect_success 'repo finds its work tree' '
-	(cd repo.git &&
-	 : > work/sub/dir/untracked &&
-	 test sub/dir/untracked = "$(git ls-files --others)")
-'
-
-test_expect_success 'repo finds its work tree from work tree, too' '
-	(cd repo.git/work/sub/dir &&
-	 : > tracked &&
-	 git --git-dir=../../.. add tracked &&
-	 cd ../../.. &&
-	 test sub/dir/tracked = "$(git ls-files)")
+test_expect_success 'setup' '
+	EMPTY_TREE=$(git write-tree) &&
+	EMPTY_BLOB=$(git hash-object -t blob --stdin </dev/null) &&
+	CHANGED_BLOB=$(echo changed | git hash-object -t blob --stdin) &&
+	ZEROES=0000000000000000000000000000000000000000 &&
+	EMPTY_BLOB7=$(echo $EMPTY_BLOB | sed "s/\(.......\).*/\1/") &&
+	CHANGED_BLOB7=$(echo $CHANGED_BLOB | sed "s/\(.......\).*/\1/") &&
+
+	mkdir -p work/sub/dir &&
+	mkdir -p work2 &&
+	mv .git repo.git
+'
+
+test_expect_success 'setup: helper for testing rev-parse' '
+	test_rev_parse() {
+		echo $1 >expected.bare &&
+		echo $2 >expected.inside-git &&
+		echo $3 >expected.inside-worktree &&
+		if test $# -ge 4
+		then
+			echo $4 >expected.prefix
+		fi &&
+
+		git rev-parse --is-bare-repository >actual.bare &&
+		git rev-parse --is-inside-git-dir >actual.inside-git &&
+		git rev-parse --is-inside-work-tree >actual.inside-worktree &&
+		if test $# -ge 4
+		then
+			git rev-parse --show-prefix >actual.prefix
+		fi &&
+
+		test_cmp expected.bare actual.bare &&
+		test_cmp expected.inside-git actual.inside-git &&
+		test_cmp expected.inside-worktree actual.inside-worktree &&
+		if test $# -ge 4
+		then
+			# rev-parse --show-prefix should output
+			# a single newline when at the top of the work tree,
+			# but we test for that separately.
+			test -z "$4" && ! test -s actual.prefix ||
+			test_cmp expected.prefix actual.prefix
+		fi
+	}
+'
+
+test_expect_success 'setup: core.worktree = relative path' '
+	unset GIT_WORK_TREE;
+	GIT_DIR=repo.git &&
+	GIT_CONFIG="$(pwd)"/$GIT_DIR/config &&
+	export GIT_DIR GIT_CONFIG &&
+	git config core.worktree ../work
+'
+
+test_expect_success 'outside' '
+	test_rev_parse false false false
+'
+
+test_expect_success 'inside work tree' '
+	(
+		cd work &&
+		GIT_DIR=../repo.git &&
+		GIT_CONFIG="$(pwd)"/$GIT_DIR/config &&
+		test_rev_parse false false true ""
+	)
+'
+
+test_expect_failure 'empty prefix is actually written out' '
+	echo >expected &&
+	(
+		cd work &&
+		GIT_DIR=../repo.git &&
+		GIT_CONFIG="$(pwd)"/$GIT_DIR/config &&
+		git rev-parse --show-prefix >../actual
+	) &&
+	test_cmp expected actual
+'
+
+test_expect_success 'subdir of work tree' '
+	(
+		cd work/sub/dir &&
+		GIT_DIR=../../../repo.git &&
+		GIT_CONFIG="$(pwd)"/$GIT_DIR/config &&
+		test_rev_parse false false true sub/dir/
+	)
+'
+
+test_expect_success 'setup: core.worktree = absolute path' '
+	unset GIT_WORK_TREE;
+	GIT_DIR=$(pwd)/repo.git &&
+	GIT_CONFIG=$GIT_DIR/config &&
+	export GIT_DIR GIT_CONFIG &&
+	git config core.worktree "$(pwd)/work"
+'
+
+test_expect_success 'outside' '
+	test_rev_parse false false false &&
+	(
+		cd work2 &&
+		test_rev_parse false false false
+	)
+'
+
+test_expect_success 'inside work tree' '
+	(
+		cd work &&
+		test_rev_parse false false true ""
+	)
+'
+
+test_expect_success 'subdir of work tree' '
+	(
+		cd work/sub/dir &&
+		test_rev_parse false false true sub/dir/
+	)
+'
+
+test_expect_success 'setup: GIT_WORK_TREE=relative (override core.worktree)' '
+	GIT_DIR=$(pwd)/repo.git &&
+	GIT_CONFIG=$GIT_DIR/config &&
+	git config core.worktree non-existent &&
+	GIT_WORK_TREE=work &&
+	export GIT_DIR GIT_CONFIG GIT_WORK_TREE
+'
+
+test_expect_success 'outside' '
+	test_rev_parse false false false &&
+	(
+		cd work2 &&
+		test_rev_parse false false false
+	)
+'
+
+test_expect_success 'inside work tree' '
+	(
+		cd work &&
+		GIT_WORK_TREE=. &&
+		test_rev_parse false false true ""
+	)
+'
+
+test_expect_success 'subdir of work tree' '
+	(
+		cd work/sub/dir &&
+		GIT_WORK_TREE=../.. &&
+		test_rev_parse false false true sub/dir/
+	)
+'
+
+test_expect_success 'setup: GIT_WORK_TREE=absolute, below git dir' '
+	mv work repo.git/work &&
+	mv work2 repo.git/work2 &&
+	GIT_DIR=$(pwd)/repo.git &&
+	GIT_CONFIG=$GIT_DIR/config &&
+	GIT_WORK_TREE=$(pwd)/repo.git/work &&
+	export GIT_DIR GIT_CONFIG GIT_WORK_TREE
+'
+
+test_expect_success 'outside' '
+	echo outside &&
+	test_rev_parse false false false
+'
+
+test_expect_success 'in repo.git' '
+	(
+		cd repo.git &&
+		test_rev_parse false true false
+	) &&
+	(
+		cd repo.git/objects &&
+		test_rev_parse false true false
+	) &&
+	(
+		cd repo.git/work2 &&
+		test_rev_parse false true false
+	)
+'
+
+test_expect_success 'inside work tree' '
+	(
+		cd repo.git/work &&
+		test_rev_parse false true true ""
+	)
+'
+
+test_expect_success 'subdir of work tree' '
+	(
+		cd repo.git/work/sub/dir &&
+		test_rev_parse false true true sub/dir/
+	)
+'
+
+test_expect_success 'find work tree from repo' '
+	echo sub/dir/untracked >expected &&
+	cat <<-\EOF >repo.git/work/.gitignore &&
+	expected.*
+	actual.*
+	.gitignore
+	EOF
+	>repo.git/work/sub/dir/untracked &&
+	(
+		cd repo.git &&
+		git ls-files --others --exclude-standard >../actual
+	) &&
+	test_cmp expected actual
+'
+
+test_expect_success 'find work tree from work tree' '
+	echo sub/dir/tracked >expected &&
+	>repo.git/work/sub/dir/tracked &&
+	(
+		cd repo.git/work/sub/dir &&
+		git --git-dir=../../.. add tracked
+	) &&
+	(
+		cd repo.git &&
+		git ls-files >../actual
+	) &&
+	test_cmp expected actual
 '
 
 test_expect_success '_gently() groks relative GIT_DIR & GIT_WORK_TREE' '
-	(cd repo.git/work/sub/dir &&
-	GIT_DIR=../../.. GIT_WORK_TREE=../.. GIT_PAGER= \
+	(
+		cd repo.git/work/sub/dir &&
+		GIT_DIR=../../.. &&
+		GIT_WORK_TREE=../.. &&
+		GIT_PAGER= &&
+		export GIT_DIR GIT_WORK_TREE GIT_PAGER &&
+
 		git diff --exit-code tracked &&
-	echo changed > tracked &&
-	! GIT_DIR=../../.. GIT_WORK_TREE=../.. GIT_PAGER= \
-		git diff --exit-code tracked)
-'
-cat > diff-index-cached.expected <<\EOF
-:000000 100644 0000000000000000000000000000000000000000 e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 A	sub/dir/tracked
-EOF
-cat > diff-index.expected <<\EOF
-:000000 100644 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000 A	sub/dir/tracked
-EOF
-
-
-test_expect_success 'git diff-index' '
-	GIT_DIR=repo.git GIT_WORK_TREE=repo.git/work git diff-index $EMPTY_TREE > result &&
-	test_cmp diff-index.expected result &&
-	GIT_DIR=repo.git git diff-index --cached $EMPTY_TREE > result &&
-	test_cmp diff-index-cached.expected result
-'
-cat >diff-files.expected <<\EOF
-:100644 100644 e69de29bb2d1d6434b8b29ae775ad8c2e48c5391 0000000000000000000000000000000000000000 M	sub/dir/tracked
-EOF
-
-test_expect_success 'git diff-files' '
-	GIT_DIR=repo.git GIT_WORK_TREE=repo.git/work git diff-files > result &&
-	test_cmp diff-files.expected result
-'
-
-cat >diff-TREE.expected <<\EOF
-diff --git a/sub/dir/tracked b/sub/dir/tracked
-new file mode 100644
-index 0000000..5ea2ed4
---- /dev/null
-+++ b/sub/dir/tracked
-@@ -0,0 +1 @@
-+changed
-EOF
-cat >diff-TREE-cached.expected <<\EOF
-diff --git a/sub/dir/tracked b/sub/dir/tracked
-new file mode 100644
-index 0000000..e69de29
-EOF
-cat >diff-FILES.expected <<\EOF
-diff --git a/sub/dir/tracked b/sub/dir/tracked
-index e69de29..5ea2ed4 100644
---- a/sub/dir/tracked
-+++ b/sub/dir/tracked
-@@ -0,0 +1 @@
-+changed
-EOF
-
-test_expect_success 'git diff' '
-	GIT_DIR=repo.git GIT_WORK_TREE=repo.git/work git diff $EMPTY_TREE > result &&
-	test_cmp diff-TREE.expected result &&
-	GIT_DIR=repo.git git diff --cached $EMPTY_TREE > result &&
-	test_cmp diff-TREE-cached.expected result &&
-	GIT_DIR=repo.git GIT_WORK_TREE=repo.git/work git diff > result &&
-	test_cmp diff-FILES.expected result
+		echo changed >tracked &&
+		test_must_fail git diff --exit-code tracked
+	)
+'
+
+test_expect_success 'diff-index respects work tree under .git dir' '
+	cat >diff-index-cached.expected <<-EOF &&
+	:000000 100644 $ZEROES $EMPTY_BLOB A	sub/dir/tracked
+	EOF
+	cat >diff-index.expected <<-EOF &&
+	:000000 100644 $ZEROES $ZEROES A	sub/dir/tracked
+	EOF
+
+	(
+		GIT_DIR=repo.git &&
+		GIT_WORK_TREE=repo.git/work &&
+		export GIT_DIR GIT_WORK_TREE &&
+		git diff-index $EMPTY_TREE >diff-index.actual &&
+		git diff-index --cached $EMPTY_TREE >diff-index-cached.actual
+	) &&
+	test_cmp diff-index.expected diff-index.actual &&
+	test_cmp diff-index-cached.expected diff-index-cached.actual
+'
+
+test_expect_success 'diff-files respects work tree under .git dir' '
+	cat >diff-files.expected <<-EOF &&
+	:100644 100644 $EMPTY_BLOB $ZEROES M	sub/dir/tracked
+	EOF
+
+	(
+		GIT_DIR=repo.git &&
+		GIT_WORK_TREE=repo.git/work &&
+		export GIT_DIR GIT_WORK_TREE &&
+		git diff-files >diff-files.actual
+	) &&
+	test_cmp diff-files.expected diff-files.actual
+'
+
+test_expect_success 'git diff respects work tree under .git dir' '
+	cat >diff-TREE.expected <<-EOF &&
+	diff --git a/sub/dir/tracked b/sub/dir/tracked
+	new file mode 100644
+	index 0000000..$CHANGED_BLOB7
+	--- /dev/null
+	+++ b/sub/dir/tracked
+	@@ -0,0 +1 @@
+	+changed
+	EOF
+	cat >diff-TREE-cached.expected <<-EOF &&
+	diff --git a/sub/dir/tracked b/sub/dir/tracked
+	new file mode 100644
+	index 0000000..$EMPTY_BLOB7
+	EOF
+	cat >diff-FILES.expected <<-EOF &&
+	diff --git a/sub/dir/tracked b/sub/dir/tracked
+	index $EMPTY_BLOB7..$CHANGED_BLOB7 100644
+	--- a/sub/dir/tracked
+	+++ b/sub/dir/tracked
+	@@ -0,0 +1 @@
+	+changed
+	EOF
+
+	(
+		GIT_DIR=repo.git &&
+		GIT_WORK_TREE=repo.git/work &&
+		export GIT_DIR GIT_WORK_TREE &&
+		git diff $EMPTY_TREE >diff-TREE.actual &&
+		git diff --cached $EMPTY_TREE >diff-TREE-cached.actual &&
+		git diff >diff-FILES.actual
+	) &&
+	test_cmp diff-TREE.expected diff-TREE.actual &&
+	test_cmp diff-TREE-cached.expected diff-TREE-cached.actual &&
+	test_cmp diff-FILES.expected diff-FILES.actual
 '
 
 test_expect_success 'git grep' '
-	(cd repo.git/work/sub &&
-	GIT_DIR=../.. GIT_WORK_TREE=.. git grep -l changed | grep dir/tracked)
+	echo dir/tracked >expected.grep &&
+	(
+		cd repo.git/work/sub &&
+		GIT_DIR=../.. &&
+		GIT_WORK_TREE=.. &&
+		export GIT_DIR GIT_WORK_TREE &&
+		git grep -l changed >../../../actual.grep
+	) &&
+	test_cmp expected.grep actual.grep
 '
 
 test_expect_success 'git commit' '
@@ -191,14 +328,14 @@ test_expect_success 'git commit' '
 
 test_expect_success 'absolute pathspec should fail gracefully' '
 	(
-		cd repo.git || exit 1
-		git config --unset core.worktree
+		cd repo.git &&
+		test_might_fail git config --unset core.worktree &&
 		test_must_fail git log HEAD -- /home
 	)
 '
 
 test_expect_success 'make_relative_path handles double slashes in GIT_DIR' '
-	: > dummy_file
+	>dummy_file
 	echo git --git-dir="$(pwd)//repo.git" --work-tree="$(pwd)" add dummy_file &&
 	git --git-dir="$(pwd)//repo.git" --work-tree="$(pwd)" add dummy_file
 '
diff --git a/t/t4111-apply-subdir.sh b/t/t4111-apply-subdir.sh
new file mode 100755
index 0000000000..a52d94ae21
--- /dev/null
+++ b/t/t4111-apply-subdir.sh
@@ -0,0 +1,142 @@
+#!/bin/sh
+
+test_description='patching from inconvenient places'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	cat >patch <<-\EOF &&
+	diff file.orig file
+	--- a/file.orig
+	+++ b/file
+	@@ -1 +1,2 @@
+	 1
+	+2
+	EOF
+	patch="$(pwd)/patch" &&
+
+	echo 1 >preimage &&
+	printf "%s\n" 1 2 >postimage &&
+	echo 3 >other &&
+
+	test_tick &&
+	git commit --allow-empty -m basis
+'
+
+test_expect_success 'setup: subdir' '
+	reset_subdir() {
+		git reset &&
+		mkdir -p sub/dir/b &&
+		mkdir -p objects &&
+		cp "$1" file &&
+		cp "$1" objects/file &&
+		cp "$1" sub/dir/file &&
+		cp "$1" sub/dir/b/file &&
+		git add file sub/dir/file sub/dir/b/file objects/file &&
+		cp "$2" file &&
+		cp "$2" sub/dir/file &&
+		cp "$2" sub/dir/b/file &&
+		cp "$2" objects/file &&
+		test_might_fail git update-index --refresh -q
+	}
+'
+
+test_expect_success 'apply from subdir of toplevel' '
+	cp postimage expected &&
+	reset_subdir other preimage &&
+	(
+		cd sub/dir &&
+		git apply "$patch"
+	) &&
+	test_cmp expected sub/dir/file
+'
+
+test_expect_success 'apply --cached from subdir of toplevel' '
+	cp postimage expected &&
+	cp other expected.working &&
+	reset_subdir preimage other &&
+	(
+		cd sub/dir &&
+		git apply --cached "$patch"
+	) &&
+	git show :sub/dir/file >actual &&
+	test_cmp expected actual &&
+	test_cmp expected.working sub/dir/file
+'
+
+test_expect_success 'apply --index from subdir of toplevel' '
+	cp postimage expected &&
+	reset_subdir preimage other &&
+	(
+		cd sub/dir &&
+		test_must_fail git apply --index "$patch"
+	) &&
+	reset_subdir other preimage &&
+	(
+		cd sub/dir &&
+		test_must_fail git apply --index "$patch"
+	) &&
+	reset_subdir preimage preimage &&
+	(
+		cd sub/dir &&
+		git apply --index "$patch"
+	) &&
+	git show :sub/dir/file >actual &&
+	test_cmp expected actual &&
+	test_cmp expected sub/dir/file
+'
+
+test_expect_success 'apply from .git dir' '
+	cp postimage expected &&
+	cp preimage .git/file &&
+	cp preimage .git/objects/file
+	(
+		cd .git &&
+		git apply "$patch"
+	) &&
+	test_cmp expected .git/file
+'
+
+test_expect_success 'apply from subdir of .git dir' '
+	cp postimage expected &&
+	cp preimage .git/file &&
+	cp preimage .git/objects/file
+	(
+		cd .git/objects &&
+		git apply "$patch"
+	) &&
+	test_cmp expected .git/objects/file
+'
+
+test_expect_success 'apply --cached from .git dir' '
+	cp postimage expected &&
+	cp other expected.working &&
+	cp other .git/file &&
+	reset_subdir preimage other &&
+	(
+		cd .git &&
+		git apply --cached "$patch"
+	) &&
+	git show :file >actual &&
+	test_cmp expected actual &&
+	test_cmp expected.working file &&
+	test_cmp expected.working .git/file
+'
+
+test_expect_success 'apply --cached from subdir of .git dir' '
+	cp postimage expected &&
+	cp preimage expected.subdir &&
+	cp other .git/file &&
+	cp other .git/objects/file &&
+	reset_subdir preimage other &&
+	(
+		cd .git/objects &&
+		git apply --cached "$patch"
+	) &&
+	git show :file >actual &&
+	git show :objects/file >actual.subdir &&
+	test_cmp expected actual &&
+	test_cmp expected.subdir actual.subdir
+'
+
+test_done