#include?“cache.h“

/*
?*?Do?not?use?this?for?inspecting?*tracked*?content.??When?path?is?a
?*?symlink?to?a?directory?we?do?not?want?to?say?it?is?a?directory?when
?*?dealing?with?tracked?content?in?the?working?tree.
?*/
int?is_directory（const?char?*path）
{
	struct?stat?st;
	return?（!stat（path?&st）?&&?S_ISDIR（st.st_mode））;
}

/*?We?allow?“recursive“?symbolic?links.?Only?within?reason?though.?*/
#define?MAXDEPTH?5

/*
?*?Return?the?real?path?（i.e.?absolute?path?with?symlinks?resolved
?*?and?extra?slashes?removed）?equivalent?to?the?specified?path.??（If
?*?you?want?an?absolute?path?but?don‘t?mind?links?use
?*?absolute_path（）.）??The?return?value?is?a?pointer?to?a?static
?*?buffer.
?*
?*?The?input?and?all?intermediate?paths?must?be?shorter?than?MAX_PATH.
?*?The?directory?part?of?path?（i.e.?everything?up?to?the?last
?*?dir_sep）?must?denote?a?valid?existing?directory?but?the?last
?*?component?need?not?exist.??If?die_on_error?is?set?then?die?with?an
?*?informative?error?message?if?there?is?a?problem.??Otherwise?return
?*?NULL?on?errors?（without?generating?any?output）.
?*
?*?If?path?is?our?buffer?then?return?path?as?it‘s?already?what?the
?*?user?wants.
?*/
static?const?char?*real_path_internal（const?char?*path?int?die_on_error）
{
	static?struct?strbuf?sb?=?STRBUF_INIT;
	char?*retval?=?NULL;

	/*
	?*?If?we?have?to?temporarily?chdir（）?store?the?original?CWD
	?*?here?so?that?we?can?chdir（）?back?to?it?at?the?end?of?the
	?*?function:
	?*/
	struct?strbuf?cwd?=?STRBUF_INIT;

	int?depth?=?MAXDEPTH;
	char?*last_elem?=?NULL;
	struct?stat?st;

	/*?We‘ve?already?done?it?*/
	if?（path?==?sb.buf）
		return?path;

	if?（!*path）?{
		if?（die_on_error）
			die（“The?empty?string?is?not?a?valid?path“）;
		else
			goto?error_out;
	}

	strbuf_reset（&sb）;
	strbuf_addstr（&sb?path）;

	while?（depth--）?{
		if?（!is_directory（sb.buf））?{
			char?*last_slash?=?find_last_dir_sep（sb.buf）;
			if?（last_slash）?{
				last_elem?=?xstrdup（last_slash?+?1）;
				strbuf_setlen（&sb?last_slash?-?sb.buf?+?1）;
			}?else?{
				last_elem?=?xmemdupz（sb.buf?sb.len）;
				strbuf_reset（&sb）;
			}
		}

		if?（sb.len）?{
			if?（!cwd.len?&&?strbuf_getcwd（&cwd））?{
				if?（die_on_error）
					die_errno（“Could?not?get?current?working?directory“）;
				else
					goto?error_out;
			}

			if?（chdir（sb.buf））?{
				if?（die_on_error）
					die_errno（“Could?not?switch?to?‘%s‘“
						??sb.buf）;
				else
					goto?error_out;
			}
		}
		if?（strbuf_getcwd（&sb））?{
			if?（die_on_error）
				die_errno（“Could?not?get?current?working?directory“）;
			else
				goto?error_out;
		}

		if?（last_elem）?{
			if?（sb.len?&&?!is_dir_sep（sb.buf[sb.len?-?1]））
				strbuf_addch（&sb?‘/‘）;
			strbuf_addstr（&sb?last_elem）;
			free（last_elem）;
			last_elem?=?NULL;
		}

		if?（!lstat（sb.buf?&st）?&&?S_ISLNK（st.st_mode））?{
			struct?strbuf?next_sb?=?STRBUF_INIT;
			ssize_t?len?=?strbuf_readlink（&next_sb?sb.buf?0）;
			if?（len?				if?（die_on_error）
					die_errno（“Invalid?symlink?‘%s‘“
						??sb.buf）;
				else
					goto?error_out;