A template in the block format registered garbage. conf_parse_file()
routed every file with an '@' in its name straight to the legacy
parser, which read the block line by line: the section header became a
service whose command was the section title, and each key = value line
below it became an environment variable.
service serv:%i { ... } -> service 'serv:eth0' with argument '{'
Substitute %i over the whole file before parsing instead, so format
detection and both parsers see finished text. A bare name@.conf is
still skipped, it is the template rather than an instance of one.
The legacy parser no longer opens the file or substitutes per line, it
is handed the instantiated buffer, so the template convention now has
one implementation instead of two. conf_is_template() applies
basenm(), a directory with an '@' in its name is not a template.
libconfuse cannot name a buffer it parses before 3.4, so a typo in a
template would be reported against "[buf]". Parse through fmemopen()
with the file name preset until the floor moves.
Signed-off-by: Joachim Wiberg <troglobit@gmail.com>