sparse-index: prevent repo root from becoming sparse

Prevent the repository root from being collapsed into a sparse directory by
treating an empty path as "inside the sparse-checkout". When collapsing a
sparse index (e.g. in 'git sparse-checkout reapply'), the root directory
typically could not become a sparse directory due to the presence of in-cone
root-level files and directories. However, if no such in-cone files or
directories were present, there was no explicit check signaling that the
"repository root path" (an empty string, in the case of
'convert_to_sparse(...)') was in-cone, and a sparse directory index entry
would be created from the repository root directory.

The documentation in Documentation/git-sparse-checkout.txt explicitly states
that the files in the root directory are expected to be in-cone for a
cone-mode sparse-checkout. Collapsing the root into a sparse directory entry
violates that assumption, as sparse directory entries are expected to be
outside the sparse cone and have SKIP_WORKTREE enabled. This invalid state
in turn causes issues with commands that interact with the index, e.g.
'git status'.

Treating an empty (root) path as in-cone prevents the creation of a root
sparse directory in 'convert_to_sparse(...)'. Because the repository root is
otherwise never compared with sparse patterns (in both cone-mode and
non-cone sparse-checkouts), the new check does not cause additional changes
to how sparse patterns are applied.

Helped-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Victoria Dye <vdye@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/dir.c b/dir.c
index d91295f2bcdcf86f0b1c41a32ac6a17d5d3cf65e..a136377eb499270c9bb91ac2c72db03d72a111a5 100644 (file)
--- a/dir.c
+++ b/dir.c
@@ -1463,10 +1463,11 @@ static int path_in_sparse_checkout_1(const char *path,
        const char *end, *slash;
 
        /*
-        * We default to accepting a path if there are no patterns or
-        * they are of the wrong type.
+        * We default to accepting a path if the path is empty, there are no
+        * patterns, or the patterns are of the wrong type.
         */
-       if (init_sparse_checkout_patterns(istate) ||
+       if (!*path ||
+           init_sparse_checkout_patterns(istate) ||
            (require_cone_mode &&
             !istate->sparse_checkout_patterns->use_cone_patterns))
                return 1;

diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index f3a059e5af557aacf113909aa06e089d9fd43e8c..9ef7cd808851e7d5e99262d29082191d9f2117a2 100755 (executable)
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -244,6 +244,24 @@ test_expect_success 'expanded in-memory index matches full index' '
        test_sparse_match git ls-files --stage
 '
 
+test_expect_success 'root directory cannot be sparse' '
+       init_repos &&
+
+       # Remove all in-cone files and directories from the index, collapse index
+       # with `git sparse-checkout reapply`
+       git -C sparse-index rm -r . &&
+       git -C sparse-index sparse-checkout reapply &&
+
+       # Verify sparse directories still present, root directory is not sparse
+       cat >expect <<-EOF &&
+       folder1/
+       folder2/
+       x/
+       EOF
+       git -C sparse-index ls-files --sparse >actual &&
+       test_cmp expect actual
+'
+
 test_expect_success 'status with options' '
        init_repos &&
        test_sparse_match ls &&