api: added edit comment api

permissions: flush all when running remap and rescan.

release: Bump version 4.19.0 to 4.20.0

pull-requests: use proper diff calculation for versioning of PRs.

caches: use better name for empty user cache, None was confusing, and looked as if it would be an error.

create: fixed case for repo groups that didn't pre-fill the repo group from GET param. - also added similar to repo selector for personal repo group.

caches: log errors when doing an initilize of DB caches.

tests: fixed some tests after recent changes.

permissions: allow users to update settings for repository groups they still own, or have admin perms, when they don't change their name. - this before gave no-permission errors as the parent group access was checked - since the group parent permission should be checked at creation, or name change this commit fixes such case

summary: fixed summary page total commits count.