abspath: move related functions to abspath

Move abspath-related functions from strbuf.[ch] to abspath.[ch] so that
strbuf is focused on string manipulation routines with minimal
dependencies.

Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

abspath.h

@@ -30,4 +30,25 @@ static inline int is_absolute_path(const char *path)
 	return is_dir_sep(path[0]) || has_dos_drive_prefix(path);
 }
 
+/**
+ * Add a path to a buffer, converting a relative path to an
+ * absolute one in the process.  Symbolic links are not
+ * resolved.
+ */
+void strbuf_add_absolute_path(struct strbuf *sb, const char *path);
+
+/**
+ * Canonize `path` (make it absolute, resolve symlinks, remove extra
+ * slashes) and append it to `sb`.  Die with an informative error
+ * message if there is a problem.
+ *
+ * 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.
+ *
+ * Callers that don't mind links should use the more lightweight
+ * strbuf_add_absolute_path() instead.
+ */
+void strbuf_add_real_path(struct strbuf *sb, const char *path);
+
 #endif /* ABSPATH_H */