sparse-index: update do_read_index to ensure correct sparsity

Unless `command_requires_full_index` forces index expansion, ensure in-core
index sparsity matches config settings on read by calling
`ensure_correct_sparsity`. This makes the behavior of the in-core index more
consistent between different methods of updating sparsity: manually changing
the `index.sparse` config setting vs. executing
`git sparse-checkout --[no-]sparse-index init`

Although index sparsity is normally updated with `git sparse-checkout init`,
ensuring correct sparsity after a manual `index.sparse` change has some
practical benefits:

1. It allows for command-by-command sparsity toggling with
   `-c index.sparse=<true|false>`, e.g. when troubleshooting issues with the
   sparse index.
2. It prevents users from experiencing abnormal slowness after setting
   `index.sparse` to `true` due to use of a full index in all commands until
   the on-disk index is updated.

Helped-by: Junio C Hamano <gitster@pobox.com>
Co-authored-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Victoria Dye <vdye@github.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/read-cache.c b/read-cache.c
index a78b88a41bf01c5fa131b2f3d6d683bff465690b..b3772ba70a13664c36b024b7acb51aaaf4d88c8f 100644 (file)
--- a/read-cache.c
+++ b/read-cache.c
@@ -2337,9 +2337,17 @@ int do_read_index(struct index_state *istate, const char *path, int must_exist)
 
        if (!istate->repo)
                istate->repo = the_repository;
+
+       /*
+        * If the command explicitly requires a full index, force it
+        * to be full. Otherwise, correct the sparsity based on repository
+        * settings and other properties of the index (if necessary).
+        */
        prepare_repo_settings(istate->repo);
        if (istate->repo->settings.command_requires_full_index)
                ensure_full_index(istate);
+       else
+               ensure_correct_sparsity(istate);
 
        return istate->cache_nr;
 

diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index ca91c6a67f8fb7223b05870be0c40c013a51f5dc..59accde1fa3d2ed4f5e858223fb01f94adaeee6e 100755 (executable)
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh
@@ -694,6 +694,37 @@ test_expect_success 'sparse-index is expanded and converted back' '
        test_region index ensure_full_index trace2.txt
 '
 
+test_expect_success 'index.sparse disabled inline uses full index' '
+       init_repos &&
+
+       # When index.sparse is disabled inline with `git status`, the
+       # index is expanded at the beginning of the execution then never
+       # converted back to sparse. It is then written to disk as a full index.
+       rm -f trace2.txt &&
+       GIT_TRACE2_EVENT="$(pwd)/trace2.txt" GIT_TRACE2_EVENT_NESTING=10 \
+               git -C sparse-index -c index.sparse=false status &&
+       ! test_region index convert_to_sparse trace2.txt &&
+       test_region index ensure_full_index trace2.txt &&
+
+       # Since index.sparse is set to true at a repo level, the index
+       # is converted from full to sparse when read, then never expanded
+       # over the course of `git status`. It is written to disk as a sparse
+       # index.
+       rm -f trace2.txt &&
+       GIT_TRACE2_EVENT="$(pwd)/trace2.txt" GIT_TRACE2_EVENT_NESTING=10 \
+               git -C sparse-index status &&
+       test_region index convert_to_sparse trace2.txt &&
+       ! test_region index ensure_full_index trace2.txt &&
+
+       # Now that the index has been written to disk as sparse, it is not
+       # converted to sparse (or expanded to full) when read by `git status`.
+       rm -f trace2.txt &&
+       GIT_TRACE2_EVENT="$(pwd)/trace2.txt" GIT_TRACE2_EVENT_NESTING=10 \
+               git -C sparse-index status &&
+       ! test_region index convert_to_sparse trace2.txt &&
+       ! test_region index ensure_full_index trace2.txt
+'
+
 ensure_not_expanded () {
        rm -f trace2.txt &&
        echo >>sparse-index/untracked.txt &&