unpack-trees: refuse to remove startup_info->original_cwd

In the past, when a directory needs to be removed to make room for a
file, we have always errored out when that directory contains any
untracked (but not ignored) files.  Add an extra condition on that: also
error out if the directory is the current working directory we inherited
from our parent process.

Acked-by: Derrick Stolee <stolee@gmail.com>
Acked-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t2501-cwd-empty.sh

@@ -113,7 +113,7 @@ test_expect_success 'checkout does not clean cwd incidentally' '
 '
 
 test_expect_success 'checkout fails if cwd needs to be removed' '
-	test_required_dir_removal failure git checkout fd_conflict
+	test_required_dir_removal success git checkout fd_conflict
 '
 
 test_expect_success 'reset --hard does not clean cwd incidentally' '
@@ -144,23 +144,17 @@ test_expect_success 'merge fails if cwd needs to be removed; recursive friendly'
 	(
 		cd dirORfile &&
 
-		# We would rather this failed, but we test for existing
-		# rather than desired behavior
-		git merge fd_conflict 2>../error
+		test_must_fail git merge fd_conflict 2>../error
 	) &&
 
-	## Here is the behavior we would rather have:
-	#test_path_is_dir dirORfile &&
-	#grep "Refusing to remove the current working directory" error
-	## But instead we test for existing behavior
-	test_path_is_file dirORfile &&
-	test_must_be_empty error
+	test_path_is_dir dirORfile &&
+	grep "Refusing to remove the current working directory" error
 '
 
 GIT_TEST_MERGE_ALGORITHM=ort
 
 test_expect_success 'merge fails if cwd needs to be removed' '
-	test_required_dir_removal failure git merge fd_conflict
+	test_required_dir_removal success git merge fd_conflict
 '
 
 test_expect_success 'cherry-pick does not clean cwd incidentally' '
@@ -168,7 +162,7 @@ test_expect_success 'cherry-pick does not clean cwd incidentally' '
 '
 
 test_expect_success 'cherry-pick fails if cwd needs to be removed' '
-	test_required_dir_removal failure git cherry-pick fd_conflict
+	test_required_dir_removal success git cherry-pick fd_conflict
 '
 
 test_expect_success 'rebase does not clean cwd incidentally' '
@@ -184,7 +178,7 @@ test_expect_success 'revert does not clean cwd incidentally' '
 '
 
 test_expect_success 'revert fails if cwd needs to be removed' '
-	test_required_dir_removal failure git revert undo_fd_conflict
+	test_required_dir_removal success git revert undo_fd_conflict
 '
 
 test_expect_success 'rm does not clean cwd incidentally' '

unpack-trees.c

@@ -36,6 +36,9 @@ static const char *unpack_plumbing_errors[NB_UNPACK_TREES_WARNING_TYPES] = {
 	/* ERROR_NOT_UPTODATE_DIR */
 	"Updating '%s' would lose untracked files in it",
 
+	/* ERROR_CWD_IN_THE_WAY */
+	"Refusing to remove '%s' since it is the current working directory.",
+
 	/* ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN */
 	"Untracked working tree file '%s' would be overwritten by merge.",
 
@@ -131,6 +134,9 @@ void setup_unpack_trees_porcelain(struct unpack_trees_options *opts,
 	msgs[ERROR_NOT_UPTODATE_DIR] =
 		_("Updating the following directories would lose untracked files in them:\n%s");
 
+	msgs[ERROR_CWD_IN_THE_WAY] =
+		_("Refusing to remove the current working directory:\n%s");
+
 	if (!strcmp(cmd, "checkout"))
 		msg = advice_enabled(ADVICE_COMMIT_BEFORE_MERGE)
 		      ? _("The following untracked working tree files would be removed by checkout:\n%%s"
@@ -2146,10 +2152,7 @@ static int verify_clean_subdirectory(const struct cache_entry *ce,
 		cnt++;
 	}
 
-	/*
-	 * Then we need to make sure that we do not lose a locally
-	 * present file that is not ignored.
-	 */
+	/* Do not lose a locally present file that is not ignored. */
 	pathbuf = xstrfmt("%.*s/", namelen, ce->name);
 
 	memset(&d, 0, sizeof(d));
@@ -2160,6 +2163,12 @@ static int verify_clean_subdirectory(const struct cache_entry *ce,
 	free(pathbuf);
 	if (i)
 		return add_rejected_path(o, ERROR_NOT_UPTODATE_DIR, ce->name);
+
+	/* Do not lose startup_info->original_cwd */
+	if (startup_info->original_cwd &&
+	    !strcmp(startup_info->original_cwd, ce->name))
+		return add_rejected_path(o, ERROR_CWD_IN_THE_WAY, ce->name);
+
 	return cnt;
 }
 

unpack-trees.h

@@ -19,6 +19,7 @@ enum unpack_trees_error_types {
 	ERROR_WOULD_OVERWRITE = 0,
 	ERROR_NOT_UPTODATE_FILE,
 	ERROR_NOT_UPTODATE_DIR,
+	ERROR_CWD_IN_THE_WAY,
 	ERROR_WOULD_LOSE_UNTRACKED_OVERWRITTEN,
 	ERROR_WOULD_LOSE_UNTRACKED_REMOVED,
 	ERROR_BIND_OVERLAP,