[PATCH v2] sequencer: pass absolute GIT_WORK_TREE to exec commands

["brian m. carlson" <sandals@crustytoothpaste.net>]

The sequencer currently passes GIT_DIR, but not GIT_WORK_TREE, to exec
commands.  In that configuration, we assume that whatever directory
we're in is the top level of the work tree, and git rev-parse
--show-toplevel responds accordingly.  However, when we're in a
subdirectory, that isn't correct: we respond with the subdirectory as
the top level, resulting in unexpected behavior.

Ensure that we pass GIT_WORK_TREE as well as GIT_DIR so that git
operations within subdirectories work correctly.

Note that we are guaranteed to have a work tree in this case: the
relevant sequencer functions are called only from revert, cherry-pick,
and rebase--helper; all of these commands require a working tree.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
---
 sequencer.c                   | 2 ++
 t/t3404-rebase-interactive.sh | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/sequencer.c b/sequencer.c
index 5354d4d51e..c8e16f9168 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2636,6 +2636,8 @@ static int do_exec(const char *command_line)
 	fprintf(stderr, "Executing: %s\n", command_line);
 	child_argv[0] = command_line;
 	argv_array_pushf(&child_env, "GIT_DIR=%s", absolute_path(get_git_dir()));
+	argv_array_pushf(&child_env, "GIT_WORK_TREE=%s",
+			 absolute_path(get_git_work_tree()));
 	status = run_command_v_opt_cd_env(child_argv, RUN_USING_SHELL, NULL,
 					  child_env.argv);
 
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 352a52e59d..d03055d149 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -119,6 +119,15 @@ test_expect_success 'rebase -i with exec allows git commands in subdirs' '
 	)
 '
 
+test_expect_success 'rebase -i sets work tree properly' '
+	test_when_finished "rm -rf subdir" &&
+	test_when_finished "test_might_fail git rebase --abort" &&
+	mkdir subdir &&
+	git rebase -x "(cd subdir && git rev-parse --show-toplevel)" HEAD^ \
+		>actual &&
+	! grep "/subdir$" actual
+'
+
 test_expect_success 'rebase -i with the exec command checks tree cleanness' '
 	git checkout master &&
 	set_fake_editor &&