rm: add --sparse option

As we did previously in 'git add', add a '--sparse' option to 'git rm'
that allows modifying paths outside of the sparse-checkout definition.
The existing checks in 'git rm' are restricted to tracked files that
have the SKIP_WORKTREE bit in the current index. Future changes will
cause 'git rm' to reject removing paths outside of the sparse-checkout
definition, even if they are untracked or do not have the SKIP_WORKTREE
bit.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rm.txt

@@ -72,6 +72,12 @@ For more details, see the 'pathspec' entry in linkgit:gitglossary[7].
 --ignore-unmatch::
 	Exit with a zero status even if no files matched.
 
+--sparse::
+	Allow updating index entries outside of the sparse-checkout cone.
+	Normally, `git rm` refuses to update index entries whose paths do
+	not fit within the sparse-checkout cone. See
+	linkgit:git-sparse-checkout[1] for more.
+
 -q::
 --quiet::
 	`git rm` normally outputs one line (in the form of an `rm` command)

builtin/rm.c

@@ -237,6 +237,7 @@ static int check_local_mod(struct object_id *head, int index_only)
 
 static int show_only = 0, force = 0, index_only = 0, recursive = 0, quiet = 0;
 static int ignore_unmatch = 0, pathspec_file_nul;
+static int include_sparse;
 static char *pathspec_from_file;
 
 static struct option builtin_rm_options[] = {
@@ -247,6 +248,7 @@ static struct option builtin_rm_options[] = {
 	OPT_BOOL('r', NULL,             &recursive,  N_("allow recursive removal")),
 	OPT_BOOL( 0 , "ignore-unmatch", &ignore_unmatch,
 				N_("exit with a zero status even if nothing matched")),
+	OPT_BOOL(0, "sparse", &include_sparse, N_("allow updating entries outside of the sparse-checkout cone")),
 	OPT_PATHSPEC_FROM_FILE(&pathspec_from_file),
 	OPT_PATHSPEC_FILE_NUL(&pathspec_file_nul),
 	OPT_END(),
@@ -298,7 +300,8 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 	ensure_full_index(&the_index);
 	for (i = 0; i < active_nr; i++) {
 		const struct cache_entry *ce = active_cache[i];
-		if (ce_skip_worktree(ce))
+
+		if (!include_sparse && ce_skip_worktree(ce))
 			continue;
 		if (!ce_path_match(&the_index, ce, &pathspec, seen))
 			continue;
@@ -322,7 +325,8 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 				seen_any = 1;
 			else if (ignore_unmatch)
 				continue;
-			else if (matches_skip_worktree(&pathspec, i, &skip_worktree_seen))
+			else if (!include_sparse &&
+				 matches_skip_worktree(&pathspec, i, &skip_worktree_seen))
 				string_list_append(&only_match_skip_worktree, original);
 			else
 				die(_("pathspec '%s' did not match any files"), original);

t/t3602-rm-sparse-checkout.sh

@@ -43,6 +43,18 @@ test_expect_success 'recursive rm does not remove sparse entries' '
 	test_cmp expected actual
 '
 
+test_expect_success 'recursive rm --sparse removes sparse entries' '
+	git reset --hard &&
+	git sparse-checkout set "sub/dir" &&
+	git rm --sparse -r sub &&
+	git status --porcelain -uno >actual &&
+	cat >expected <<-\EOF &&
+	D  sub/d
+	D  sub/dir/e
+	EOF
+	test_cmp expected actual
+'
+
 test_expect_success 'rm obeys advice.updateSparsePath' '
 	git reset --hard &&
 	git sparse-checkout set a &&