scmutil: match no longer accepts repo objects

scmutil: switch match users to supplying contexts The most appropriate context is not always clearly defined. The obvious cases: For working directory commands, we use None For commands (eg annotate) with single revs, we use that revision The less obvious cases: For commands (eg status, diff) with a pair of revs, we use the second revision For commands that take a range (like log), we use None

scmutil: match now accepts a context or a repo

context: add a match builder method This is groundwork for matching against filesets in contexts