fastexport: simple improvements
The main purpose of this series is to fix an inconsistency between git and hg commit messages. All conversion tools add a newline to hg commit messages, see for example (hg-git, git-remote-hg, and hg-fast-export.
hg fastexport
should do the same.
While at it, I reorganized the code of write_data()
a little bit.
Edited by Felipe Contreras