I found I couldn't craft a usable ges-launch rendering description from the existing help text. Here's a possible improved version:

Usage:
  lt-ges-launch-0.10 [OPTION...] [timeline] - plays or renders a timeline.

ges-launch renders a timeline, which can be specified on the commandline,
or loaded from a file using the -q option.

A timeline is a list of files, patterns, and transitions to be rendered
one after the other. Files and Patterns provide video and audio as the
primary input, and transitions animate between the end of one file/pattern
and the beginning of a new one. Hence, transitions can only be listed
in between patterns or files.

A file is a triplet of filename, inpoint (in seconds) and
duration (in seconds). If the duration is 0, the full file length is used.

Patterns and transitions are triplets that begin with either "+pattern"
or "+transition", followed by a <type> and duration (in seconds, must be
greater than 0)

Durations in all cases can be fractions of a second.

Example:
ges-launch file1.avi 0 45 +transition crossfade 3.5 file2.avi 0 0