largefiles: fix test and check code

histedit: always abort with same message when working dir is wrong. Using only one message makes live easier for translators. The clearer error message was supposed by Augie Fackler.

histedit: report when revisions to edit are not ancestors of working dir Editing the history only is possible when the working dir is a descendant of the revisions to edit. When this happens explain it by writing abort: %s is not an ancestor of working directory

Merge

manifestmerge: handle abort on local unknown, remote created files This replaces the _checkunknown call in calculateupdates with a more performant version. On a repository with over 150,000 files, this speeds up an update by 0.6-0.8 seconds, which is up to 25%. This does not introduce any UI changes. There is existing test coverage for every case, mostly in test-merge*.t.

manifestmerge: pass in branchmerge and force separately This will be used in an upcoming patch.

manifest: use a size 3 LRU cache to store parsed manifests Previously, the manifest cache would store the last manifest parsed. We could run into situations with operations like update where we would try parsing the manifest for a revision r1, then r2, then r1 again. This increases the cache size to 3 to avoid that bit of performance fragility.

util: add an LRU cache dict In certain cases we would like to have a cache of the last N results of a given computation, where N is small. This will be used in an upcoming patch to increase the size of the manifest cache from 1 to 3.