hgweb: test the order of archive links

revlog: REVIDX_EXTSTORED flag This flag will be used by the lfs extension to mark the revision data as stored externally.

revlog: flag processor Add the ability for revlog objects to process revision flags and apply registered transforms on read/write operations. This patch introduces: - the 'revlog._processflags()' method that looks at revision flags and applies flag processors registered on them. Due to the need to handle non-commutative operations, flag transforms are applied in stable order but the order in which the transforms are applied is reversed between read and write operations. - the 'addflagprocessor()' method allowing to register processors on flags. Flag processors are defined as a 3-tuple of (read, write, raw) functions to be applied depending on the operation being performed. - an update on 'revlog.addrevision()' behavior. The current flagprocessor design relies on extensions to wrap around 'addrevision()' to set flags on revision data, and on the flagprocessor to perform the actual transformation of its contents. In the lfs case, this means we need to process flags before we meet the 2GB size check, leading to performing some operations before it happens: - if flags are set on the revision data, we assume some extensions might be modifying the contents using the flag processor next, and we compute the node for the original revision data (still allowing extension to override the node by wrapping around 'addrevision()'). - we then invoke the flag processor to apply registered transforms (in lfs's case, drastically reducing the size of large blobs). - finally, we proceed with the 2GB size check. Note: In the case a cachedelta is passed to 'addrevision()' and we detect the flag processor modified the revision data, we chose to trust the flag processor and drop the cachedelta.

revlog: pass revlog flags to addrevision Adding the ability to passing flags to addrevision instead of simply passing default flags to _addrevision will allow extensions relying on flag transforms to wrap around addrevision() in order to update revlog flags. The first use case of this patch will be the lfs extension marking nodes as stored externally when the contents are larger than the defined threshold. One of the reasons leading to setting flags in addrevision() wrappers in the flag processor design is that it allows to detect files larger than the 2GB limit before the check is performed, which allows lfs to transform the contents into metadata.

revlog: add 'raw' argument to revision and _addrevision This patch introduces a new 'raw' argument (defaults to False) to revlog's revision() and _addrevision() methods. When the 'raw' argument is set to True, it indicates the revision data should be handled as raw data by the flagprocessor. Note: Given revlog.addgroup() calls are restricted to changegroup generation, we can always set raw to True when calling revlog._addrevision() from revlog.addgroup().

pager: do not special case chg Since chg has its own _runpager implementation, it's no longer necessary to special-case chg in the pager extension. This will effectively enable the new chg pager code path that runs inside runcommand.

chg: remove getpager support We have enough bits to switch to the new chg pager code path in runcommand. So just remove the legacy getpager support. This is a red-only patch, and will break chg's pager support temporarily.

chgserver: implement chgui._runpager This patch implements chgui._runpager in a relatively simple way. A more clean way is to move the core logic of "attachio" to "ui", which will be done later after chg runs uisetup per request.