templates: make {indent("", " ")} be empty
indent() is documented to indent all non-empty lines, but it made an
exception for the first line, which always got indented. I also made
indent() not indent the first line even if an indent override was
given for the first line. I think that is what one would usually want.
Differential Revision: https://phab.mercurial-scm.org/D7432
(binary:application/octet-stream)