exchange: parse requirements from stream clone specification string Stream clone bundles can only be consumed if the consumer supports the exact format requirements that were present on the producer. This patch adds support for encoding and verifying the format requirements on the bundle specification string for a stream clone bundle are supported by the local repository. If they aren't, we raise an UnsupportedBundleSpecification, just like we do when an unknown compression or bundle type is encountered. The impetus for this patch is so the clone bundles manifest can advertise stream clone bundles and so clients can filter out stream clones with unsupported format requirements. e.g. a stream clone produced with the not-yet-invented "revlogv2" format will be ignored by clients that only support "revlogv1."

exchange: support parameters in bundle specification strings Sometimes a basic type string is not sufficient for representing the contents of a bundle. Take bundle2 for example: future bundle2 files may contain parts that today's bundle2 parser can't read. Another example is stream clone data. These require clients to support specific repository formats or they won't be able to read the written files. In both scenarios, we need to describe additional metadata beyond the outer container type. Furthermore, this metadata behaves more like an unordered set, so an order-based declaration format (such as static strings) is not sufficient. We introduce support for "parameters" into the bundle specification string. These are essentially key-value pairs that can be used to encode additional metadata about the bundle. Semicolons are used as the delimiter partially to increase similarity to MIME parameter values (see RFC 2231) and because they are relatively safe from the command line (although values will need quotes to avoid interpretation as multiple shell commands). Alternatives considered were spaces (a bit annoying to encode) and '&' (similar to URL query strings) (which will do bad things in a shell if unquoted). The parsing function now returns a dict of parsed parameters and consumers have been updated accordingly.

commands: support consuming stream clone bundles For the same reasons that we don't produce stream clone bundles with `hg bundle`, we don't support consuming stream clone bundles with `hg unbundle`. We introduce a complementary debug command for applying stream clone bundles. This command is mostly to facilitate testing. Although it may be used to manually apply stream clone bundles until a more formal mechanism is (possibly) adopted.