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
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state