* Refactor Cron and merge dashboard tasks

* Merge Cron and Dashboard tasks
* Make every cron task report a system notice on completion
* Refactor the creation of these tasks
* Ensure that execution counts of tasks is correct
* Allow cron tasks to be started from the cron page

* golangci-lint fixes

* Enforce that only one task with the same name can be registered

Signed-off-by: Andrew Thornton <art27@cantab.net>

* fix name check

Signed-off-by: Andrew Thornton <art27@cantab.net>

* as per @guillep2k

* as per @lafriks

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Add git.CommandContext variants

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

* Add `gitea doctor --list` flag to list the checks that will be run, including those by default
* Add `gitea doctor --run` to run specific checks
* Add `gitea doctor --all` to run all checks
* Add db version checker
* Add non-default recalculate merge bases check/fixer to doctor
* Add hook checker (Fix #9878) and ensure hooks are executable (Fix #6319)
* Fix authorized_keys checker - slight change of functionality here because parsing the command is fragile and we should just check if the authorized_keys file is essentially the same as what gitea would produce. (This is still not perfect as order matters - we should probably just md5sum the two files.)
* Add SCRIPT_TYPE check (Fix #10977)
* Add `gitea doctor --fix` to attempt to fix what is possible to easily fix
* Add `gitea doctor --log-file` to set the log-file, be it a file, stdout or to switch off completely. (Fixes previously undetected bug with certain xorm logging configurations - see @6543 comment.)

Signed-off-by: Andrew Thornton <art27@cantab.net>

* test -x is not enough https://stackoverflow.com/a/39489087

Move more general repository functions out of models/repo.go