revset: fix alias substitution recursion (issue3240) The revset aliases expansion worked like: expr = "some revset" for alias in aliases: expr = alias.process(expr) where "process" was replacing the alias with its *unexpanded* substitution, recursively. So it only worked when aliases were applied in proper dependency order. This patch rewrites the expansion process so all aliases are expanded recursively at every tree level, after parent alias rewriting and variable expansion.

update: just merge unknown file collisions The unknown file collision rule was introduced as an extension of the "should be clean when merging" rule. Unfortunately, it got applied to the normal update path, which should be happy to merge local changes. This patch gives us merges for unknown file collisions on update, while preserving abort for merge and update -c.

merge: don't use unknown() This removes use of unknown files for building the synthetic working directory manifest used by manifestmerge. Instead, we adopt the strategy used by _checkunknown. Side-effect: unknown files are no longer moved by remote directory renames, and now are left alone like ignored files.

merge: refactor unknown file conflict checking Previously, we would do a full working directory walk including unknown files to perform a merge. In many cases, this was painful because unknown files greatly outnumbered tracked files and generally had no useful effect on the merge. Here we instead wait until we find a file in the destination that's not tracked locally and detect if it exists and is not ignored. This is usually cheaper but can be -more- expensive in the case where we're adding a huge number of files. On the other hand, the cost of statting the new files should be dwarfed by the cost of eventually writing them. In this version, case collisions are detected implicitly by os.path.exists and wctx[f] lookup.

update: use normal update path with --check (issue2450) This avoids clobbering unknown files on update by not using overwrite mode.

fetch: use update rather than clean when updating (issue3246) We already verify the working directory is "clean" before starting so there's no advantage to clobbering the working directory.