obshistory: use formatter instead of ui.write in the debugobshistory command Replace ui.write with a formater to have template support and json output. Update tests to assert json outputs.

ui: Fix hg stack json output Previously 'hg stack -Tjson' generated invalid output like: [ { "isentry": true, "topic.stack.desc": "...", "topic.stack.index": 1, "topic.stack.state": "current", "topic.stack.state.symbol": "@" } ] , { "isentry": true, "topic.stack.desc": "...", "topic.stack.index": 1, "topic.stack.state": "current", "topic.stack.state.symbol": "@" }, { "isentry": false, "topic.stack.desc": "...", "topic.stack.state": "base", "topic.stack.state.symbol": "^" } ] I de-indented the fmt.end() to generate this output: [ { "isentry": true, "topic.stack.desc": "...", "topic.stack.index": 1, "topic.stack.state": "current", "topic.stack.state.symbol": "@" }, { "isentry": false, "topic.stack.desc": "...", "topic.stack.state": "base", "topic.stack.state.symbol": "^" } ] I've also added a test case.