mq: correctly make an empty line after description in new patches
There would in some cases be an empty line between headers and the description -
that does not seem right.
There should also be an empty line between description and diff - but that was
missing.
These two mistakes would sometimes make it up for each other so we fix both at
once to just show the improvement.
Instead of writing an extra newline when writing a header line, write an extra
line when it not is written as a part of the description but is necessary
anyway.
$ hg init repo
$ cd repo
$ touch foo
$ hg ci -Am 'add foo'
adding foo
$ hg up -C null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
this should be stored as a delta against rev 0
$ echo foo bar baz > foo
$ hg ci -Am 'add foo again'
adding foo
created new head
$ hg debugindex foo
rev offset length ..... linkrev nodeid p1 p2 (re)
0 0 0 ..... 0 b80de5d13875 000000000000 000000000000 (re)
1 0 24 ..... 1 0376abec49b8 000000000000 000000000000 (re)
$ cd ..