[PATCH] reset: behave correctly with sparse-checkout

[PATCH] reset: behave correctly with sparse-checkout

[Derrick Stolee via GitGitGadget]

From: Kevin Willford <kewillf@microsoft.com>

When using the sparse checkout feature, 'git reset' will add entries to
the index that will have the skip-worktree bit off but will leave the
working directory empty. File data is lost because the index version of
the files has been changed but there is nothing that is in the working
directory. This will cause the next 'git status' call to show either
deleted for files modified or deleting or nothing for files added. The
added files should be shown as untracked and modified files should be
shown as modified.

To fix this when the reset is running if there is not a file in the
working directory and if it will be missing with the new index entry or
was not missing in the previous version, we create the previous index
version of the file in the working directory so that status will report
correctly and the files will be availble for the user to deal with.

This fixes a documented failure from t1092 that was created in 19a0acc
(t1092: test interesting sparse-checkout scenarios, 2021-01-23).

Signed-off-by: Kevin Willford <kewillf@microsoft.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
    reset: behave correctly with sparse-checkout
    
    This is a version of a commit [1] that has been in the microsoft/git
    fork for a while (authored in March 2017). I finally got around to
    figuring out why a test marked as 'test_expect_failure' was succeeding
    in our fork by bisecting to this commit.
    
    I only made superficial modifications from Kevin's original commit. Some
    style things, including whitespace and variable names, plus the switch
    to 'test_expect_success' in t1092.
    
    [1]
    https://github.com/microsoft/git/commit/6b8a074edfe3f4c06d08c3e1f2e496d3aef0a056
    
    Thanks, Stolee

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1047%2Fderrickstolee%2Fsparse-checkout%2Freset-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1047/derrickstolee/sparse-checkout/reset-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1047

 builtin/reset.c                          | 39 +++++++++++++++
 t/t1092-sparse-checkout-compatibility.sh |  4 +-
 t/t7114-reset-sparse-checkout.sh         | 61 ++++++++++++++++++++++++
 3 files changed, 101 insertions(+), 3 deletions(-)
 create mode 100755 t/t7114-reset-sparse-checkout.sh

diff --git a/builtin/reset.c b/builtin/reset.c
index 51c9e2f43ff..8ffcd713720 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -25,6 +25,8 @@
 #include "cache-tree.h"
 #include "submodule.h"
 #include "submodule-config.h"
+#include "dir.h"
+#include "entry.h"
 
 #define REFRESH_INDEX_DELAY_WARNING_IN_MS (2 * 1000)
 
@@ -127,12 +129,49 @@ static void update_index_from_diff(struct diff_queue_struct *q,
 		struct diff_options *opt, void *data)
 {
 	int i;
+	int pos;
 	int intent_to_add = *(int *)data;
 
 	for (i = 0; i < q->nr; i++) {
 		struct diff_filespec *one = q->queue[i]->one;
+		struct diff_filespec *two = q->queue[i]->two;
 		int is_missing = !(one->mode && !is_null_oid(&one->oid));
+		int was_missing = !two->mode && is_null_oid(&two->oid);
 		struct cache_entry *ce;
+		struct cache_entry *ce_before;
+		struct checkout state = CHECKOUT_INIT;
+
+		/*
+		 * When using the sparse-checkout feature the cache entries
+		 * that are added here will not have the skip-worktree bit
+		 * set. Without this code there is data that is lost because
+		 * the files that would normally be in the working directory
+		 * are not there and show as deleted for the next status.
+		 * In the case of added files, they just disappear.
+		 *
+		 * We need to create the previous version of the files in
+		 * the working directory so that they will have the right
+		 * content and the next status call will show modified or
+		 * untracked files correctly.
+		 */
+		if (core_apply_sparse_checkout && !file_exists(two->path)) {
+			pos = cache_name_pos(two->path, strlen(two->path));
+			if ((pos >= 0 && ce_skip_worktree(active_cache[pos])) &&
+			    (is_missing || !was_missing)) {
+				state.force = 1;
+				state.refresh_cache = 1;
+				state.istate = &the_index;
+
+				ce_before = make_cache_entry(&the_index, two->mode,
+							     &two->oid, two->path,
+							     0, 0);
+				if (!ce_before)
+					die(_("make_cache_entry failed for path '%s'"),
+						two->path);
+
+				checkout_entry(ce_before, &state, NULL, NULL);
+			}
+		}
 
 		if (is_missing && !intent_to_add) {
 			remove_file_from_cache(one->path);
diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 886e78715fe..c5977152661 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -459,9 +459,7 @@ test_expect_failure 'blame with pathspec outside sparse definition' '
 	test_all_match git blame deep/deeper2/deepest/a
 '
 
-# NEEDSWORK: a sparse-checkout behaves differently from a full checkout
-# in this scenario, but it shouldn't.
-test_expect_failure 'checkout and reset (mixed)' '
+test_expect_success 'checkout and reset (mixed)' '
 	init_repos &&
 
 	test_all_match git checkout -b reset-test update-deep &&
diff --git a/t/t7114-reset-sparse-checkout.sh b/t/t7114-reset-sparse-checkout.sh
new file mode 100755
index 00000000000..a8029707fb1
--- /dev/null
+++ b/t/t7114-reset-sparse-checkout.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+
+test_description='reset when using a sparse-checkout'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_tick &&
+	echo "checkout file" >c &&
+	echo "modify file" >m &&
+	echo "delete file" >d &&
+	git add . &&
+	git commit -m "initial commit" &&
+	echo "added file" >a &&
+	echo "modification of a file" >m &&
+	git rm d &&
+	git add . &&
+	git commit -m "second commit" &&
+	git checkout -b endCommit
+'
+
+test_expect_success 'reset when there is a sparse-checkout' '
+	echo "/c" >.git/info/sparse-checkout &&
+	test_config core.sparsecheckout true &&
+	git checkout -B resetBranch &&
+	test_path_is_missing m &&
+	test_path_is_missing a &&
+	test_path_is_missing d &&
+	git reset HEAD~1 &&
+	echo "checkout file" >expect &&
+	test_cmp expect c &&
+	echo "added file" >expect &&
+	test_cmp expect a &&
+	echo "modification of a file" >expect &&
+	test_cmp expect m &&
+	test_path_is_missing d
+'
+
+test_expect_success 'reset after deleting file without skip-worktree bit' '
+	git checkout -f endCommit &&
+	git clean -xdf &&
+	cat >.git/info/sparse-checkout <<-\EOF &&
+	/c
+	/m
+	EOF
+	test_config core.sparsecheckout true &&
+	git checkout -B resetAfterDelete &&
+	test_path_is_file m &&
+	test_path_is_missing a &&
+	test_path_is_missing d &&
+	rm -f m &&
+	git reset HEAD~1 &&
+	echo "checkout file" >expect &&
+	test_cmp expect c &&
+	echo "added file" >expect &&
+	test_cmp expect a &&
+	test_path_is_missing m &&
+	test_path_is_missing d
+'
+
+test_done

base-commit: ddb1055343948e0d0bc81f8d20245f1ada6430a0
-- 
gitgitgadget

Re: [PATCH] reset: behave correctly with sparse-checkout

[Derrick Stolee]

On 9/28/2021 11:20 AM, Derrick Stolee via GitGitGadget wrote:
> From: Kevin Willford <kewillf@microsoft.com>
> 
> When using the sparse checkout feature, 'git reset' will add entries to
> the index that will have the skip-worktree bit off but will leave the
> working directory empty. File data is lost because the index version of
> the files has been changed but there is nothing that is in the working
> directory. This will cause the next 'git status' call to show either
> deleted for files modified or deleting or nothing for files added. The
> added files should be shown as untracked and modified files should be
> shown as modified.

Sorry for the noise, but hold off on this patch. It will be joining
a larger series involving getting 'git reset' working with the sparse
index.

Thanks,
-Stolee