histedit: allow "-" as a command file When "-" is specified as a command file, we read rules from stdin. Alter a single test to demo the behavior, but most of them could benefit from this. There is minor change in test output resulting from the fact we no longer change log messages.

histedit: properly handle --continue on empty fold When all changes from the fold have been dropped, the --continue code was confused. This changeset handles this case. The test for this case existed but was broken.

histedit-test: replace obscure python script by a plain file One of the tests uses a python script to edit the histedit commands on the fly. It was hard to read and likely to break. This is replaced by a plain command file. Doing so made me discover that the python script is incorrect. The "+6" regexp never matched because the revision number is wrong. This error is kept in the replacement for now. Fixing the histedit command triggers a traceback in histedit. A later changeset will fix the error and restore the intended test.

test: improve documentation of some histedit tests Each test section is clearly separated from the others and gains some helpful documentation.

test: use a lighter log style in histedit test The default log displays a log of information that is useless for histedit tests. Having a cleaner log help readability of those tests a lot. This does not change anything to the test semantic.

subrepo: add regression test for issue3870