add/rm: allow adding sparse entries when virtual

Upstream, a20f704 (add: warn when asked to update SKIP_WORKTREE entries,
2021-04-08) modified how 'git add <pathspec>' works with cache entries
marked with the SKIP_WORKTREE bit. The intention is to prevent a user
from accidentally adding a path that is outside their sparse-checkout
definition but somehow matches an existing index entry.

A similar change for 'git rm' happened in d5f4b82 (rm: honor sparse
checkout patterns, 2021-04-08).

This breaks when using the virtual filesystem in VFS for Git. It is
rare, but we could be in a scenario where the user has staged a change
and then the file is projected away. If the user re-adds the file, then
this warning causes the command to fail with the advise message.

Disable this logic when core_virtualfilesystem is enabled.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

builtin/add.c

@@ -1,9 +1,12 @@
+#define USE_THE_REPOSITORY_VARIABLE
+
 /*
  * "git add" builtin command
  *
  * Copyright (C) 2006 Linus Torvalds
  */
 #include "builtin.h"
+#include "environment.h"
 #include "advice.h"
 #include "config.h"
 #include "lockfile.h"
@@ -46,6 +49,7 @@ static int chmod_pathspec(struct repository *repo,
 		int err;
 
 		if (!include_sparse &&
+		    !core_virtualfilesystem &&
 		    (ce_skip_worktree(ce) ||
 		     !path_in_sparse_checkout(ce->name, repo->index)))
 			continue;
@@ -131,8 +135,9 @@ static int refresh(struct repository *repo, int verbose, const struct pathspec *
 		if (!seen[i]) {
 			const char *path = pathspec->items[i].original;
 
-			if (matches_skip_worktree(pathspec, i, &skip_worktree_seen) ||
-			    !path_in_sparse_checkout(path, repo->index)) {
+			if (!core_virtualfilesystem &&
+			    (matches_skip_worktree(pathspec, i, &skip_worktree_seen) ||
+			     !path_in_sparse_checkout(path, repo->index))) {
 				string_list_append(&only_match_skip_worktree,
 						   pathspec->items[i].original);
 			} else {
@@ -142,7 +147,11 @@ static int refresh(struct repository *repo, int verbose, const struct pathspec *
 		}
 	}
 
-	if (only_match_skip_worktree.nr) {
+	/*
+	 * When using a virtual filesystem, we might re-add a path
+	 * that is currently virtual and we want that to succeed.
+	 */
+	if (!core_virtualfilesystem && only_match_skip_worktree.nr) {
 		advise_on_updating_sparse_paths(&only_match_skip_worktree);
 		ret = 1;
 	}
@@ -527,7 +536,11 @@ int cmd_add(int argc,
 			if (seen[i])
 				continue;
 
-			if (!include_sparse &&
+			/*
+			 * When using a virtual filesystem, we might re-add a path
+			 * that is currently virtual and we want that to succeed.
+			 */
+			if (!include_sparse && !core_virtualfilesystem &&
 			    matches_skip_worktree(&pathspec, i, &skip_worktree_seen)) {
 				string_list_append(&only_match_skip_worktree,
 						   pathspec.items[i].original);
@@ -551,7 +564,6 @@ int cmd_add(int argc,
 			}
 		}
 
-
 		if (only_match_skip_worktree.nr) {
 			advise_on_updating_sparse_paths(&only_match_skip_worktree);
 			exit_status = 1;

builtin/rm.c

@@ -5,6 +5,7 @@
  */
 #define USE_THE_REPOSITORY_VARIABLE
 #include "builtin.h"
+#include "environment.h"
 #include "advice.h"
 #include "config.h"
 #include "lockfile.h"
@@ -314,7 +315,7 @@ int cmd_rm(int argc,
 	for (i = 0; i < the_repository->index->cache_nr; i++) {
 		const struct cache_entry *ce = the_repository->index->cache[i];
 
-		if (!include_sparse &&
+		if (!include_sparse && !core_virtualfilesystem &&
 		    (ce_skip_worktree(ce) ||
 		     !path_in_sparse_checkout(ce->name, the_repository->index)))
 			continue;
@@ -351,7 +352,11 @@ int cmd_rm(int argc,
 				    *original ? original : ".");
 		}
 
-		if (only_match_skip_worktree.nr) {
+		/*
+		 * When using a virtual filesystem, we might re-add a path
+		 * that is currently virtual and we want that to succeed.
+		 */
+		if (!core_virtualfilesystem && only_match_skip_worktree.nr) {
 			advise_on_updating_sparse_paths(&only_match_skip_worktree);
 			ret = 1;
 		}

read-cache.c

@@ -3968,7 +3968,7 @@ static void update_callback(struct diff_queue_struct *q,
 		struct diff_filepair *p = q->queue[i];
 		const char *path = p->one->path;
 
-		if (!data->include_sparse &&
+		if (!data->include_sparse && !core_virtualfilesystem &&
 		    !path_in_sparse_checkout(path, data->index))
 			continue;