count-objects: report unused files in $GIT_DIR/worktrees/...

In linked checkouts, borrowed parts like config is taken from
$GIT_COMMON_DIR. $GIT_DIR/config is never used. Report them as
garbage.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/count-objects.c

@@ -70,8 +70,10 @@ int cmd_count_objects(int argc, const char **argv, const char *prefix)
 	/* we do not take arguments other than flags for now */
 	if (argc)
 		usage_with_options(count_objects_usage, opts);
-	if (verbose)
+	if (verbose) {
 		report_garbage = real_report_garbage;
+		report_linked_checkout_garbage();
+	}
 
 	for_each_loose_file_in_objdir(get_object_directory(),
 				      count_loose, count_cruft, NULL, NULL);

cache.h

@@ -695,6 +695,7 @@ extern const char *mkpath(const char *fmt, ...) __attribute__((format (printf, 1
 extern const char *git_path(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
 extern const char *git_path_submodule(const char *path, const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
+extern void report_linked_checkout_garbage(void);
 
 /*
  * Return the name of the file in the local object database that would

path.c

@@ -4,6 +4,7 @@
 #include "cache.h"
 #include "strbuf.h"
 #include "string-list.h"
+#include "dir.h"
 
 static int get_st_mode_bits(const char *path, int *mode)
 {
@@ -91,9 +92,9 @@ static void replace_dir(struct strbuf *buf, int len, const char *newdir)
 }
 
 static const char *common_list[] = {
-	"/branches", "/hooks", "/info", "/logs", "/lost-found", "/modules",
+	"/branches", "/hooks", "/info", "!/logs", "/lost-found", "/modules",
 	"/objects", "/refs", "/remotes", "/worktrees", "/rr-cache", "/svn",
-	"config", "gc.pid", "packed-refs", "shallow",
+	"config", "!gc.pid", "packed-refs", "shallow",
 	NULL
 };
 
@@ -107,6 +108,8 @@ static void update_common_dir(struct strbuf *buf, int git_dir_len)
 	for (p = common_list; *p; p++) {
 		const char *path = *p;
 		int is_dir = 0;
+		if (*path == '!')
+			path++;
 		if (*path == '/') {
 			path++;
 			is_dir = 1;
@@ -122,6 +125,28 @@ static void update_common_dir(struct strbuf *buf, int git_dir_len)
 	}
 }
 
+void report_linked_checkout_garbage(void)
+{
+	struct strbuf sb = STRBUF_INIT;
+	const char **p;
+	int len;
+
+	if (!git_common_dir_env)
+		return;
+	strbuf_addf(&sb, "%s/", get_git_dir());
+	len = sb.len;
+	for (p = common_list; *p; p++) {
+		const char *path = *p;
+		if (*path == '!')
+			continue;
+		strbuf_setlen(&sb, len);
+		strbuf_addstr(&sb, path);
+		if (file_exists(sb.buf))
+			report_garbage("unused in linked checkout", sb.buf);
+	}
+	strbuf_release(&sb);
+}
+
 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 {
 	const char *base = buf->buf + git_dir_len;