[PATCH v2 2/7] status: fix nested sparse directory diff in sparse index

["Victoria Dye via GitGitGadget" <gitgitgadget@gmail.com>]

From: Victoria Dye <vdye@github.com>

Add the 'recursive' flag to 'wt_status_collect_changes_index(...)'. Without
the 'recursive' flag, 'git status' could report index changes incorrectly
when the following conditions were met:

* sparse index is enabled
* there is a difference between the index and HEAD in a file inside a
  *subdirectory* of a sparse directory
* the sparse directory index entry is *not* expanded in-core

In this scenario, 'git status' would not recurse into the sparse directory's
subdirectories to identify which file contained the difference between the
index and HEAD. Instead, it would report the immediate subdirectory itself
as "modified".

Example:

$ git init
$ mkdir -p sparse/sub
$ echo test >sparse/sub/foo
$ git add .
$ git commit -m "commit 1"
$ echo somethingelse >sparse/sub/foo
$ git add .
$ git commit -a -m "commit 2"
$ git sparse-checkout set --cone --sparse-index 'sparse'
$ git reset --soft HEAD~1
$ git status
On branch master
You are in a sparse checkout.

Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        modified:   sparse/sub

The 'recursive' diff option in 'wt_status_collect_changes_index' corrects
this by indicating that 'git status' should recurse into sparse directories
to find modified files. Given the same repository setup as the example
above, the corrected result of `git status` is:

$ git status
On branch master
You are in a sparse checkout.

Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        modified:   sparse/sub/foo

Signed-off-by: Victoria Dye <vdye@github.com>
---
 t/t1092-sparse-checkout-compatibility.sh | 7 +++++++
 wt-status.c                              | 9 +++++++++
 2 files changed, 16 insertions(+)

diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 9ef7cd80885..b1dcaa0e642 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -278,6 +278,13 @@ test_expect_success 'status with options' '
 	test_all_match git status --porcelain=v2 -uno
 '
 
+test_expect_success 'status with diff in unexpanded sparse directory' '
+	init_repos &&
+	test_all_match git checkout rename-base &&
+	test_all_match git reset --soft rename-out-to-out &&
+	test_all_match git status --porcelain=v2
+'
+
 test_expect_success 'status reports sparse-checkout' '
 	init_repos &&
 	git -C sparse-checkout status >full &&
diff --git a/wt-status.c b/wt-status.c
index 335e723a71e..4a5b9beeca1 100644
--- a/wt-status.c
+++ b/wt-status.c
@@ -651,6 +651,15 @@ static void wt_status_collect_changes_index(struct wt_status *s)
 	rev.diffopt.detect_rename = s->detect_rename >= 0 ? s->detect_rename : rev.diffopt.detect_rename;
 	rev.diffopt.rename_limit = s->rename_limit >= 0 ? s->rename_limit : rev.diffopt.rename_limit;
 	rev.diffopt.rename_score = s->rename_score >= 0 ? s->rename_score : rev.diffopt.rename_score;
+
+	/*
+	 * The `recursive` option must be enabled to show differences in files
+	 * *more than* one level deep in a sparse directory index entry (e.g., given
+	 * sparse directory 'sparse-dir/', reporting a difference in the file
+	 * 'sparse-dir/another-dir/my-file').
+	 */
+	rev.diffopt.flags.recursive = 1;
+
 	copy_pathspec(&rev.prune_data, &s->pathspec);
 	run_diff_index(&rev, 1);
 	object_array_clear(&rev.pending);
-- 
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