Kill off get_relative_cwd()

Function dir_inside_of() does something similar (correctly), but looks
easier to understand and does not bundle cwd to its business. Given
get_relative_cwd's only user is is_inside_dir, we can kill it for
good.

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

dir.c

@@ -1001,53 +1001,6 @@ int file_exists(const char *f)
 }
 
 /*
- * get_relative_cwd() gets the prefix of the current working directory
- * relative to 'dir'.  If we are not inside 'dir', it returns NULL.
- *
- * As a convenience, it also returns NULL if 'dir' is already NULL.  The
- * reason for this behaviour is that it is natural for functions returning
- * directory names to return NULL to say "this directory does not exist"
- * or "this directory is invalid".  These cases are usually handled the
- * same as if the cwd is not inside 'dir' at all, so get_relative_cwd()
- * returns NULL for both of them.
- *
- * Most notably, get_relative_cwd(buffer, size, get_git_work_tree())
- * unifies the handling of "outside work tree" with "no work tree at all".
- */
-char *get_relative_cwd(char *buffer, int size, const char *dir)
-{
-	char *cwd = buffer;
-
-	if (!dir)
-		return NULL;
-	if (!getcwd(buffer, size))
-		die_errno("can't find the current directory");
-
-	if (!is_absolute_path(dir))
-		dir = make_absolute_path(dir);
-
-	while (*dir && *dir == *cwd) {
-		dir++;
-		cwd++;
-	}
-	if (*dir)
-		return NULL;
-	switch (*cwd) {
-	case '\0':
-		return cwd;
-	case '/':
-		return cwd + 1;
-	default:
-		/*
-		 * dir can end with a path separator when it's root
-		 * directory. Return proper prefix in that case.
-		 */
-		if (dir[-1] == '/')
-			return cwd;
-		return NULL;
-	}
-}
-
  * Given two normalized paths (a trailing slash is ok), if subdir is
  * outside dir, return -1.  Otherwise return the offset in subdir that
  * can be used as relative path to dir.
@@ -1081,8 +1034,12 @@ int dir_inside_of(const char *subdir, const char *dir)
 
 int is_inside_dir(const char *dir)
 {
-	char buffer[PATH_MAX];
-	return get_relative_cwd(buffer, sizeof(buffer), dir) != NULL;
+	char cwd[PATH_MAX];
+	if (!dir)
+		return 0;
+	if (!getcwd(cwd, sizeof(cwd)))
+		die_errno("can't find the current directory");
+	return dir_inside_of(cwd, dir) >= 0;
 }
 
 int is_empty_dir(const char *path)

dir.h

@@ -81,7 +81,6 @@ extern void add_exclude(const char *string, const char *base,
 extern void free_excludes(struct exclude_list *el);
 extern int file_exists(const char *);
 
-extern char *get_relative_cwd(char *buffer, int size, const char *dir);
 extern int is_inside_dir(const char *dir);
 extern int dir_inside_of(const char *subdir, const char *dir);