rm: honor sparse checkout patterns

`git add` refrains from adding or updating index entries that are
outside the current sparse checkout, but `git rm` doesn't follow the
same restriction. This is somewhat counter-intuitive and inconsistent.
So make `rm` honor the sparsity rules and advise on how to remove
SKIP_WORKTREE entries just like `add` does. Also add some tests for the
new behavior.

Suggested-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/advice.txt

@@ -120,6 +120,7 @@ advice.*::
 		Advice shown if a user runs the add command without providing
 		the pathspec parameter.
 	updateSparsePath::
-		Advice shown when linkgit:git-add[1] is asked to update index
-		entries outside the current sparse checkout.
+		Advice shown when either linkgit:git-add[1] or linkgit:git-rm[1]
+		is asked to update index entries outside the current sparse
+		checkout.
 --

Documentation/git-rm.txt

@@ -23,7 +23,9 @@ branch, and no updates to their contents can be staged in the index,
 though that default behavior can be overridden with the `-f` option.
 When `--cached` is given, the staged content has to
 match either the tip of the branch or the file on disk,
-allowing the file to be removed from just the index.
+allowing the file to be removed from just the index. When
+sparse-checkouts are in use (see linkgit:git-sparse-checkout[1]),
+`git rm` will only remove paths within the sparse-checkout patterns.
 
 
 OPTIONS

builtin/rm.c

@@ -5,6 +5,7 @@
  */
 #define USE_THE_INDEX_COMPATIBILITY_MACROS
 #include "builtin.h"
+#include "advice.h"
 #include "config.h"
 #include "lockfile.h"
 #include "dir.h"
@@ -254,7 +255,7 @@ static struct option builtin_rm_options[] = {
 int cmd_rm(int argc, const char **argv, const char *prefix)
 {
 	struct lock_file lock_file = LOCK_INIT;
-	int i;
+	int i, ret = 0;
 	struct pathspec pathspec;
 	char *seen;
 
@@ -295,6 +296,8 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 
 	for (i = 0; i < active_nr; i++) {
 		const struct cache_entry *ce = active_cache[i];
+		if (ce_skip_worktree(ce))
+			continue;
 		if (!ce_path_match(&the_index, ce, &pathspec, seen))
 			continue;
 		ALLOC_GROW(list.entry, list.nr + 1, list.alloc);
@@ -308,24 +311,34 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 	if (pathspec.nr) {
 		const char *original;
 		int seen_any = 0;
+		char *skip_worktree_seen = NULL;
+		struct string_list only_match_skip_worktree = STRING_LIST_INIT_NODUP;
+
 		for (i = 0; i < pathspec.nr; i++) {
 			original = pathspec.items[i].original;
-			if (!seen[i]) {
-				if (!ignore_unmatch) {
-					die(_("pathspec '%s' did not match any files"),
-					    original);
-				}
-			}
-			else {
+			if (seen[i])
 				seen_any = 1;
-			}
+			else if (ignore_unmatch)
+				continue;
+			else if (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);
+
 			if (!recursive && seen[i] == MATCHED_RECURSIVELY)
 				die(_("not removing '%s' recursively without -r"),
 				    *original ? original : ".");
 		}
 
+		if (only_match_skip_worktree.nr) {
+			advise_on_updating_sparse_paths(&only_match_skip_worktree);
+			ret = 1;
+		}
+		free(skip_worktree_seen);
+		string_list_clear(&only_match_skip_worktree, 0);
+
 		if (!seen_any)
-			exit(0);
+			exit(ret);
 	}
 
 	if (!index_only)
@@ -405,5 +418,5 @@ int cmd_rm(int argc, const char **argv, const char *prefix)
 			       COMMIT_LOCK | SKIP_IF_UNCHANGED))
 		die(_("Unable to write new index file"));
 
-	return 0;
+	return ret;
 }

t/t3602-rm-sparse-checkout.sh

@@ -0,0 +1,78 @@
+#!/bin/sh
+
+test_description='git rm in sparse checked out working trees'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' "
+	mkdir -p sub/dir &&
+	touch a b c sub/d sub/dir/e &&
+	git add -A &&
+	git commit -m files &&
+
+	cat >sparse_error_header <<-EOF &&
+	The following pathspecs didn't match any eligible path, but they do match index
+	entries outside the current sparse checkout:
+	EOF
+
+	cat >sparse_hint <<-EOF &&
+	hint: Disable or modify the sparsity rules if you intend to update such entries.
+	hint: Disable this message with \"git config advice.updateSparsePath false\"
+	EOF
+
+	echo b | cat sparse_error_header - >sparse_entry_b_error &&
+	cat sparse_entry_b_error sparse_hint >b_error_and_hint
+"
+
+for opt in "" -f --dry-run
+do
+	test_expect_success "rm${opt:+ $opt} does not remove sparse entries" '
+		git sparse-checkout set a &&
+		test_must_fail git rm $opt b 2>stderr &&
+		test_cmp b_error_and_hint stderr &&
+		git ls-files --error-unmatch b
+	'
+done
+
+test_expect_success 'recursive rm does not remove sparse entries' '
+	git reset --hard &&
+	git sparse-checkout set sub/dir &&
+	git rm -r sub &&
+	git status --porcelain -uno >actual &&
+	echo "D  sub/dir/e" >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success 'rm obeys advice.updateSparsePath' '
+	git reset --hard &&
+	git sparse-checkout set a &&
+	test_must_fail git -c advice.updateSparsePath=false rm b 2>stderr &&
+	test_cmp sparse_entry_b_error stderr
+'
+
+test_expect_success 'do not advice about sparse entries when they do not match the pathspec' '
+	git reset --hard &&
+	git sparse-checkout set a &&
+	test_must_fail git rm nonexistent 2>stderr &&
+	grep "fatal: pathspec .nonexistent. did not match any files" stderr &&
+	! grep -F -f sparse_error_header stderr
+'
+
+test_expect_success 'do not warn about sparse entries when pathspec matches dense entries' '
+	git reset --hard &&
+	git sparse-checkout set a &&
+	git rm "[ba]" 2>stderr &&
+	test_must_be_empty stderr &&
+	git ls-files --error-unmatch b &&
+	test_must_fail git ls-files --error-unmatch a
+'
+
+test_expect_success 'do not warn about sparse entries with --ignore-unmatch' '
+	git reset --hard &&
+	git sparse-checkout set a &&
+	git rm --ignore-unmatch b 2>stderr &&
+	test_must_be_empty stderr &&
+	git ls-files --error-unmatch b
+'
+
+test_done

t/t7011-skip-worktree-reading.sh

@@ -132,11 +132,6 @@ test_expect_success 'diff-files does not examine skip-worktree dirty entries' '
 	test -z "$(git diff-files -- one)"
 '
 
-test_expect_success 'git-rm succeeds on skip-worktree absent entries' '
-	setup_absent &&
-	git rm 1
-'
-
 test_expect_success 'commit on skip-worktree absent entries' '
 	git reset &&
 	setup_absent &&