read-cache: set sparsity when index is new

When the index read in 'do_read_index()' does not exist on-disk, mark the
index "sparse" if the executing command does not require a full index and
sparse index is otherwise enabled.

Some commands (such as 'git stash -u') implicitly create a new index (when
the 'GIT_INDEX_FILE' variable points to a non-existent file) and perform
some operation on it. However, when this index is created, it isn't created
with the same sparsity settings as the repo index. As a result, while these
indexes may be sparse during the operation, they are always expanded before
being written to disk. We can avoid that expansion by defaulting the index
to "sparse", in which case it will only be expanded if the full index is
needed.

Note that the function 'set_new_index_sparsity()' is created despite having
only a single caller because additional callers will be added in a
subsequent patch.

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

diff --git a/read-cache.c b/read-cache.c
index 4df97e185e9c80cd061ab1d00143eceed81a0242..60355f5ad6a9a689fd02cd98f126e084c2c74216 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -2260,6 +2260,20 @@ static unsigned long load_cache_entries_threaded(struct index_state *istate, con
        return consumed;
 }
 
+static void set_new_index_sparsity(struct index_state *istate)
+{
+       /*
+        * If the index's repo exists, mark it sparse according to
+        * repo settings.
+        */
+       if (istate->repo) {
+               prepare_repo_settings(istate->repo);
+               if (!istate->repo->settings.command_requires_full_index &&
+                   is_sparse_index_allowed(istate, 0))
+                       istate->sparse_index = 1;
+       }
+}
+
 /* remember to discard_cache() before reading a different cache! */
 int do_read_index(struct index_state *istate, const char *path, int must_exist)
 {
@@ -2281,8 +2295,10 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
        istate->timestamp.nsec = 0;
        fd = open(path, O_RDONLY);
        if (fd < 0) {
-               if (!must_exist && errno == ENOENT)
+               if (!must_exist && errno == ENOENT) {
+                       set_new_index_sparsity(istate);
                        return 0;
+               }
                die_errno(_("%s: index file open failed"), path);
        }
 

diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index 75d844cd71df8dad1cff66a9e87c06ccf1942536..85c6a56f1b7e0bca0fa54f994f95ce5436f53abc 100755 (executable)
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -1389,7 +1389,7 @@ test_expect_success 'sparse-index is not expanded: stash' '
        ensure_not_expanded stash drop stash@{0} &&
 
        echo >>sparse-index/deep/new &&
-       ! ensure_not_expanded stash -u &&
+       ensure_not_expanded stash -u &&
        (
                WITHOUT_UNTRACKED_TXT=1 &&
                ! ensure_not_expanded stash pop