Harden the sparse-checkout builtin

Documentation/git-sparse-checkout.txt

@@ -50,6 +50,14 @@ To avoid interfering with other worktrees, it first enables the
 +
 When the `--stdin` option is provided, the patterns are read from
 standard in as a newline-delimited list instead of from the arguments.
++
+When `core.sparseCheckoutCone` is enabled, the input list is considered a
+list of directories instead of sparse-checkout patterns. The command writes
+patterns to the sparse-checkout file to include all files contained in those
+directories (recursively) as well as files that are siblings of ancestor
+directories. The input format matches the output of `git ls-tree --name-only`.
+This includes interpreting pathnames that begin with a double quote (") as
+C-style quoted strings.
 
 'disable'::
 	Disable the `core.sparseCheckout` config setting, and restore the
@@ -106,7 +114,7 @@ The full pattern set allows for arbitrary pattern matches and complicated
 inclusion/exclusion rules. These can result in O(N*M) pattern matches when
 updating the index, where N is the number of patterns and M is the number
 of paths in the index. To combat this performance issue, a more restricted
-pattern set is allowed when `core.spareCheckoutCone` is enabled.
+pattern set is allowed when `core.sparseCheckoutCone` is enabled.
 
 The accepted patterns in the cone pattern set are:
 
@@ -128,9 +136,12 @@ the following patterns:
 ----------------
 
 This says "include everything in root, but nothing two levels below root."
-If we then add the folder `A/B/C` as a recursive pattern, the folders `A` and
-`A/B` are added as parent patterns. The resulting sparse-checkout file is
-now
+
+When in cone mode, the `git sparse-checkout set` subcommand takes a list of
+directories instead of a list of sparse-checkout patterns. In this mode,
+the command `git sparse-checkout set A/B/C` sets the directory `A/B/C` as
+a recursive pattern, the directories `A` and `A/B` are added as parent
+patterns. The resulting sparse-checkout file is now
 
 ----------------
 /*

builtin/clone.c

@@ -1130,7 +1130,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 	if (option_required_reference.nr || option_optional_reference.nr)
 		setup_reference();
 
-	if (option_sparse_checkout && git_sparse_checkout_init(repo))
+	if (option_sparse_checkout && git_sparse_checkout_init(dir))
 		return 1;
 
 	remote = remote_get(option_origin);

builtin/sparse-checkout.c

@@ -13,6 +13,7 @@
 #include "resolve-undo.h"
 #include "unpack-trees.h"
 #include "wt-status.h"
+#include "quote.h"
 
 static const char *empty_base = "";
 
@@ -77,8 +78,10 @@ static int sparse_checkout_list(int argc, const char **argv)
 
 		string_list_sort(&sl);
 
-		for (i = 0; i < sl.nr; i++)
-			printf("%s\n", sl.items[i].string);
+		for (i = 0; i < sl.nr; i++) {
+			quote_c_style(sl.items[i].string, NULL, stdout, 0);
+			printf("\n");
+		}
 
 		return 0;
 	}
@@ -140,6 +143,22 @@ static int update_working_directory(struct pattern_list *pl)
 	return result;
 }
 
+static char *escaped_pattern(char *pattern)
+{
+	char *p = pattern;
+	struct strbuf final = STRBUF_INIT;
+
+	while (*p) {
+		if (is_glob_special(*p))
+			strbuf_addch(&final, '\\');
+
+		strbuf_addch(&final, *p);
+		p++;
+	}
+
+	return strbuf_detach(&final, NULL);
+}
+
 static void write_cone_to_file(FILE *fp, struct pattern_list *pl)
 {
 	int i;
@@ -164,10 +183,11 @@ static void write_cone_to_file(FILE *fp, struct pattern_list *pl)
 	fprintf(fp, "/*\n!/*/\n");
 
 	for (i = 0; i < sl.nr; i++) {
-		char *pattern = sl.items[i].string;
+		char *pattern = escaped_pattern(sl.items[i].string);
 
 		if (strlen(pattern))
 			fprintf(fp, "%s/\n!%s/*/\n", pattern, pattern);
+		free(pattern);
 	}
 
 	string_list_clear(&sl, 0);
@@ -185,8 +205,9 @@ static void write_cone_to_file(FILE *fp, struct pattern_list *pl)
 	string_list_remove_duplicates(&sl, 0);
 
 	for (i = 0; i < sl.nr; i++) {
-		char *pattern = sl.items[i].string;
+		char *pattern = escaped_pattern(sl.items[i].string);
 		fprintf(fp, "%s/\n", pattern);
+		free(pattern);
 	}
 }
 
@@ -199,6 +220,10 @@ static int write_patterns_and_update(struct pattern_list *pl)
 	int result;
 
 	sparse_filename = get_sparse_checkout_filename();
+
+	if (safe_create_leading_directories(sparse_filename))
+		die(_("failed to create directory for sparse-checkout file"));
+
 	fd = hold_lock_file_for_update(&lk, sparse_filename,
 				      LOCK_DIE_ON_ERROR);
 
@@ -419,8 +444,21 @@ static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
 		pl.use_cone_patterns = 1;
 
 		if (set_opts.use_stdin) {
-			while (!strbuf_getline(&line, stdin))
+			struct strbuf unquoted = STRBUF_INIT;
+			while (!strbuf_getline(&line, stdin)) {
+				if (line.buf[0] == '"') {
+					strbuf_reset(&unquoted);
+					if (unquote_c_style(&unquoted, line.buf, NULL))
+						die(_("unable to unquote C-style string '%s'"),
+						line.buf);
+
+					strbuf_swap(&unquoted, &line);
+				}
+
 				strbuf_to_cone_pattern(&line, &pl);
+			}
+
+			strbuf_release(&unquoted);
 		} else {
 			for (i = 0; i < argc; i++) {
 				strbuf_setlen(&line, 0);

dir.c

@@ -630,11 +630,42 @@ int pl_hashmap_cmp(const void *unused_cmp_data,
 	return strncmp(ee1->pattern, ee2->pattern, min_len);
 }
 
+static char *dup_and_filter_pattern(const char *pattern)
+{
+	char *set, *read;
+	size_t count  = 0;
+	char *result = xstrdup(pattern);
+
+	set = result;
+	read = result;
+
+	while (*read) {
+		/* skip escape characters (once) */
+		if (*read == '\\')
+			read++;
+
+		*set = *read;
+
+		set++;
+		read++;
+		count++;
+	}
+	*set = 0;
+
+	if (count > 2 &&
+	    *(set - 1) == '*' &&
+	    *(set - 2) == '/')
+		*(set - 2) = 0;
+
+	return result;
+}
+
 static void add_pattern_to_hashsets(struct pattern_list *pl, struct path_pattern *given)
 {
 	struct pattern_entry *translated;
 	char *truncated;
 	char *data = NULL;
+	const char *prev, *cur, *next;
 
 	if (!pl->use_cone_patterns)
 		return;
@@ -651,17 +682,57 @@ static void add_pattern_to_hashsets(struct pattern_list *pl, struct path_pattern
 		return;
 	}
 
+	if (given->patternlen <= 2 ||
+	    *given->pattern == '*' ||
+	    strstr(given->pattern, "**")) {
+		/* Not a cone pattern. */
+		warning(_("unrecognized pattern: '%s'"), given->pattern);
+		goto clear_hashmaps;
+	}
+
+	prev = given->pattern;
+	cur = given->pattern + 1;
+	next = given->pattern + 2;
+
+	while (*cur) {
+		/* Watch for glob characters '*', '\', '[', '?' */
+		if (!is_glob_special(*cur))
+			goto increment;
+
+		/* But only if *prev != '\\' */
+		if (*prev == '\\')
+			goto increment;
+
+		/* But allow the initial '\' */
+		if (*cur == '\\' &&
+		    is_glob_special(*next))
+			goto increment;
+
+		/* But a trailing '/' then '*' is fine */
+		if (*prev == '/' &&
+		    *cur == '*' &&
+		    *next == 0)
+			goto increment;
+
+		/* Not a cone pattern. */
+		warning(_("unrecognized pattern: '%s'"), given->pattern);
+		goto clear_hashmaps;
+
+	increment:
+		prev++;
+		cur++;
+		next++;
+	}
+
 	if (given->patternlen > 2 &&
 	    !strcmp(given->pattern + given->patternlen - 2, "/*")) {
 		if (!(given->flags & PATTERN_FLAG_NEGATIVE)) {
 			/* Not a cone pattern. */
-			pl->use_cone_patterns = 0;
 			warning(_("unrecognized pattern: '%s'"), given->pattern);
 			goto clear_hashmaps;
 		}
 
-		truncated = xstrdup(given->pattern);
-		truncated[given->patternlen - 2] = 0;
+		truncated = dup_and_filter_pattern(given->pattern);
 
 		translated = xmalloc(sizeof(struct pattern_entry));
 		translated->pattern = truncated;
@@ -695,7 +766,7 @@ static void add_pattern_to_hashsets(struct pattern_list *pl, struct path_pattern
 
 	translated = xmalloc(sizeof(struct pattern_entry));
 
-	translated->pattern = xstrdup(given->pattern);
+	translated->pattern = dup_and_filter_pattern(given->pattern);
 	translated->patternlen = given->patternlen;
 	hashmap_entry_init(&translated->ent,
 			   ignore_case ?