Ordinary shell conditionals with "if" or "case" aren't actually safe in configure.ac; it's sometimes necessary to use AS_IF, AS_CASE. Ideally, we should do that consistently across all projects.
Here's a start on that: making that change to just telepathy-glib.
Created attachment 65501 [details] [review]
1/3] configure.ac: don't rely on test -a
test EXPR -a EXPR is a common extension (present in bash, dash etc.), but
is not guaranteed by POSIX.
Created attachment 65502 [details] [review]
2/3] configure.ac: use AS_IF instead of if/then/[else/]fi
AS_IF is always safe, whereas if/fi usually works in practice, but
sometimes fails to do the right thing with Autoconf macro dependencies.
See <https://bugzilla.gnome.org/show_bug.cgi?id=681413> for more
Created attachment 65503 [details] [review]
3/3] configure.ac: use AS_CASE instead of case/esac
This is the same as AS_IF, but for "case". It's safer for the same
I've edited http://telepathy.freedesktop.org/wiki/Style to recommend AS_IF, AS_CASE.
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Fixed in git for 0.19.7, thanks. I've opened many clones for our other non-obsolete Autotools projects.