record: check that we are not committing a merge before patch selection
It might sound like a good idea to use record to filter changes when merging.
If someone attemps this, it's better to tell her "no" right ahead, before the
patch generation/line selection, so she does not spend time doing it just to
receive a red light after that (sometimes rather long) process.
adding foo
adding bar
adding baz
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
created new head
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
created new head
% fail with three heads
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
abort: branch 'default' has 3 heads - please merge with an explicit rev
(run 'hg heads .' to see heads)
% close one of the heads
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
% succeed with two open heads
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)