tests: add test for path conflicts during update Differential Revision: https://phab.mercurial-scm.org/D786

context: also consider path conflicts when clearing unknown files When clearing unknown files to remove path conflicts, also delete files that conflict with the target file's path. Differential Revision: https://phab.mercurial-scm.org/D785

merge: check for path conflicts when merging (issue5628) When merging, check for any path conflicts introduced by the manifest merge and rename the conflicting file to a safe name. Differential Revision: https://phab.mercurial-scm.org/D784

util: add safename function for generating safe names to rename to This function finds a name which does not clash with any other name in the manifest, and so can be used to safely rename a file. Differential Revision: https://phab.mercurial-scm.org/D783

merge: improve error messages for path conflicts during update Differential Revision: https://phab.mercurial-scm.org/D782

merge: check for path conflicts when updating (issue5628) When updating to a new revision, check for path conflicts caused by unknown files in the working directory, and handle these by backing up the file or directory and replacing it. Differential Revision: https://phab.mercurial-scm.org/D781

merge: rename conflicts to fileconflicts in _checkunknownfiles We will need to distinguish between file conflicts and path conflicts. Rename the conflicts variable so that it will be clearly distinct from pathconflicts, which will be introduced in a future commit. Differential Revision: https://phab.mercurial-scm.org/D780

merge: add _checkunknowndirs function for detecting path conflicts Add a new function which, given a file name, finds the shortest path for which there is a conflicting file or directory in the working directory. Differential Revision: https://phab.mercurial-scm.org/D779