revset: document the regular expression support for tag(name)
This has been supported since
20f55613fb2a, in 2.3.
help: let 'hg help debug' show the list of secret debug commands
The names of the debug commands are not easy to remember and they are not easy
to find.
tests: add run-tests --changed option for running tests changed in revisions
Convenient when polishing patches and changing details of how they change test
output.
This will probably break in weird ways for revsets with special quoting ... but
it is good enough for run-tests.
Usage example:
yes | ./run-tests.py -li --changed qparent