revset: improve filter argument handling

commands: format is a Python2.6 function

debugbuilddag: build a changelog dag from a concise description Useful in tests to quickly build a complex DAG in an empty repo. Handles local tags and named branches. Options to, at each rev, - create a new file, - overwrite the same file, - append to the same file, - write to a specific line in a mergeable file. Can run shell commands during DAG buildup.

debugdag and debugindexdag: emit changelog/revlog DAGs as concise text Mainly useful for reusing DAGs somewhere else, for example for attaching them to a bug report, or for importing them into other environments (like my test environment for incoming/outgoing discovery).