Adding the option to
`checkout-index` (and changing the corresponding default behavior to respect
the `skip-worktree` bit) is especially helpful for sparse-checkout: it
prevents inadvertent creation of *all* files outside the sparse definition
on disk and eliminates the need to expand a sparse index by default when
using the `--all` option.

Internal usage of `checkout-index` in `git stash` and `git filter-branch` do
not make explicit use of files with `skip-worktree` enabled, so
`--ignore-skip-worktree-bits` is not added to them.

Signed-off-by: Victoria Dye <redacted>
---
 Documentation/git-checkout-index.txt     | 11 +++++++++--
 builtin/checkout-index.c                 | 12 ++++++++++--
 t/t1092-sparse-checkout-compatibility.sh | 10 +++++-----
 3 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/Documentation/git-checkout-index.txt b/Documentation/git-checkout-index.txt
index 4d33e7be0f5..2815f3d4b19 100644
--- a/Documentation/git-checkout-index.txt
+++ b/Documentation/git-checkout-index.txt

@@ -12,6 +12,7 @@ SYNOPSIS
 'git checkout-index' [-u] [-q] [-a] [-f] [-n] [--prefix=<string>]
                   [--stage=<number>|all]
                   [--temp]
+                  [--ignore-skip-worktree-bits]
                   [-z] [--stdin]
                   [--] [<file>...]

@@ -37,8 +38,9 @@ OPTIONS

 -a::
 --all::
-       checks out all files in the index.  Cannot be used
-       together with explicit filenames.
+       checks out all files in the index except for those with the
+       skip-worktree bit set (see `--ignore-skip-worktree-bits`).
+       Cannot be used together with explicit filenames.

 -n::
 --no-create::

@@ -59,6 +61,11 @@ OPTIONS
        write the content to temporary files.  The temporary name
        associations will be written to stdout.

+--ignore-skip-worktree-bits::
+       Check out all files, including those with the skip-worktree bit
+       set. Note: may only be used with `--all`; skip-worktree is
+       ignored when explicit filenames are specified.

+
 --stdin::
        Instead of taking list of paths from the command line,
        read list of paths from the standard input.  Paths are

diff --git a/builtin/checkout-index.c b/builtin/checkout-index.c
index e21620d964e..2053a80103a 100644
--- a/builtin/checkout-index.c
+++ b/builtin/checkout-index.c

@@ -7,6 +7,7 @@
 #define USE_THE_INDEX_COMPATIBILITY_MACROS
 #include "builtin.h"
 #include "config.h"
+#include "dir.h"
 #include "lockfile.h"
 #include "quote.h"
 #include "cache-tree.h"

@@ -116,7 +117,7 @@ static int checkout_file(const char *name, const char *prefix)
        return -1;
 }

-static int checkout_all(const char *prefix, int prefix_length)
+static int checkout_all(const char *prefix, int prefix_length, int ignore_skip_worktree)
 {
        int i, errs = 0;
        struct cache_entry *last_ce = NULL;

@@ -125,6 +126,8 @@ static int checkout_all(const char *prefix, int prefix_length)
        ensure_full_index(&the_index);
        for (i = 0; i < active_nr ; i++) {
                struct cache_entry *ce = active_cache[i];
+               if (!ignore_skip_worktree && ce_skip_worktree(ce))
+                       continue;

                if (ce_stage(ce) != checkout_stage
                    && (CHECKOUT_ALL != checkout_stage || !ce_stage(ce)))
                        continue;

@@ -176,6 +179,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
        int i;
        struct lock_file lock_file = LOCK_INIT;
        int all = 0;
+       int ignore_skip_worktree = 0;
        int read_from_stdin = 0;
        int prefix_length;
        int force = 0, quiet = 0, not_new = 0;

@@ -185,6 +189,8 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
        struct option builtin_checkout_index_options[] = {
                OPT_BOOL('a', "all", &all,
                        N_("check out all files in the index")),
+               OPT_BOOL(0, "ignore-skip-worktree-bits", &ignore_skip_worktree,
+                       N_("do not skip files with skip-worktree set")),
                OPT__FORCE(&force, N_("force overwrite of existing files"), 0),
                OPT__QUIET(&quiet,
                        N_("no warning for existing files and files not in index")),

@@ -247,6 +253,8 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)

                if (all)
                        die("git checkout-index: don't mix '--all' and explicit filenames");
+               if (ignore_skip_worktree)
+                       die("git checkout-index: don't mix '--ignore-skip-worktree-bits' and explicit filenames");
                if (read_from_stdin)
                        die("git checkout-index: don't mix '--stdin' and explicit filenames");
                p = prefix_path(prefix, prefix_length, arg);

@@ -280,7 +288,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
        }

        if (all)
-               err |= checkout_all(prefix, prefix_length);
+               err |= checkout_all(prefix, prefix_length, ignore_skip_worktree);

        if (pc_workers > 1)
                err |= run_parallel_checkout(&state, pc_workers, pc_threshold,

diff --git a/t/t1092-sparse-checkout-compatibility.sh b/t/t1092-sparse-checkout-compatibility.sh
index db7ad41109b..fad61d96107 100755
--- a/t/t1092-sparse-checkout-compatibility.sh
+++ b/t/t1092-sparse-checkout-compatibility.sh

@@ -799,14 +799,14 @@ test_expect_success 'checkout-index with folders' '
        test_all_match test_must_fail git checkout-index -f -- folder1/
 '

-# NEEDSWORK: even in sparse checkouts, checkout-index --all will create all
-# files (even those outside the sparse definition) on disk. However, these files
-# don't appear in the percentage of tracked files in git status.
-test_expect_failure 'checkout-index --all' '
+test_expect_success 'checkout-index --all' '
        init_repos &&

        test_all_match git checkout-index --all &&
-       test_sparse_match test_path_is_missing folder1
+       test_sparse_match test_path_is_missing folder1 &&
+
+       test_all_match git checkout-index --ignore-skip-worktree-bits --all &&
+       test_all_match test_path_exists folder1