filemerge: make capability check for internal tools ignore merge-tools section This is follow up of 4d7b11877dd0. Before this patch, capability check of internal merge tools falls back to _toolbool(), which examines configurations in "merge-tools" section. But "hg help config" explicitly says that "merge-tools" section configures external merge tools. Therefore, this patch makes capability check for internal tools in hascapability() always ignore configurations in merge-tools section. In this patch, command line configurations below are added at tests in tests/test-merge-tools.t, in order to confirm that explicit configuration is intentionally ignored at tool selection. --config merge-tools.:INTERNAL_TOOL.CAPABILITY=true