index: create function for deleting node from nodetree A node is marked deleted by nt_insert(self, node, -1), but "-1" could mean so many things (notably nullrev), so let's hide it in a function. The function could possibly also remove nodes from the tree in the future (it currently only marks them deleted). Differential Revision: https://phab.mercurial-scm.org/D4004

revlog: remove some knowledge of sentinel nullid in index I think the "-2" to mean "last position in index, not counting the null revision at the end" is an implementation detail of the index that we should avoid spreading knowledge of. I hope we can even remove support for index[-2]. Differential Revision: https://phab.mercurial-scm.org/D4016

scmutil: make shortest() respect disambiguation revset The previous patch would let you use a shorter prefix if the prefix is unique within a configured revset. However, that's not very useful if there's no simple way of knowing what that shorter prefix is. This patch adapts the shortest() template function to use the shorter prefixes for nodes in the configured revset. This is currently extremely slow, because it calculates the revset for each call to shortest(). To make this faster, the next patch will start caching the revset instance. Ideally we'd cache a prefix tree instance instead. Differential Revision: https://phab.mercurial-scm.org/D4038

lookup: add option to disambiguate prefix within revset When resolving a nodeid prefix that is not unique within the repo and the user has configured a revset that they want to disambiguate within, we now try to look up within that revset before we fail. If there is a unique match within the revset, we use that. This is of course most effective at allowing a short prefix if the revset contains few nodes. For most of our internal users at Google, "not public()" is sufficiently small that a hex digit or two is enough. The implementation is currently pretty slow, but good enough for small revsets (which is the expected use case). The scan in the revset is linear. We may want to use a prefix tree if we want to allow users to use a larger revset. Credit for the idea goes to Kyle Lippincott. Differential Revision: https://phab.mercurial-scm.org/D4037

revlog: use specialized exception for ambiguous prefix lookup It's useful to be able to catch a specific exception for this case. We'll use it soon. Differential Revision: https://phab.mercurial-scm.org/D4036

narrowspec: remove the unused _parsestoredpatterns() function Previous patch started using sparse.parseconfig() to read narrowspec and now we don't need this function. Differential Revision: https://phab.mercurial-scm.org/D4058

narrowspec: use sparse.parseconfig() to parse narrowspec file (BC) This also make narrow files use 'include' and 'exclude' instead of plural forms which are 'includes' and 'excludes'. This is BC because existing narrowspecs have to replace excludes, includes words with exclude and include i.e. their singular versions. Differential Revision: https://phab.mercurial-scm.org/D4057

sparse: add an action argument to parseconfig() This will help us in reusing this function to parse narrow config files and unfiying the config file parsing logic. Differential Revision: https://phab.mercurial-scm.org/D4056

tests: avoid unnecessarily looking inside .hg/ in test-narrow* Many of the narrow tests were looking at .hg/narrowspec. I think most of them were written before we added `hg tracked`, but now that we have that command, we should fix the tests. There were also a few instances of tests looking at .hg/dirstate. I fixed those to use `hg files` instead. Differential Revision: https://phab.mercurial-scm.org/D4093

narrow: extract part of narrowspec backup to core Just a little preparation for the next patch. Differential Revision: https://phab.mercurial-scm.org/D4095