Merge with stable.

manifestmerge: local unknown, remote created: don't traverse symlinks To figure out what to do with locally unknown files, Mercurial attempts to read them if they exist. When an attempt is made to read a file that exists but traverses a symlink, Mercurial aborts. With this patch, we first ensure that the file doesn't traverse a symlink before opening it. This is fine because a file being "remote created" means the symlink doesn't exist remotely, which means it will be deleted in the apply phase.

subrepo: open files in 'rb' mode to read exact data in (issue3926) Before this patch, "subrepo._calcfilehash()" opens files by "open()" without any mode specification. This implies "text mode" on Windows. When target file contains '\x00' byte, "read()" in "text mode" reads file contents in without data after '\x00'. This causes invalid SHA1 hash calculation in "subrepo._calcfilehash()". This patch opens files in 'rb' mode to read exact data in.

patch: use scmutil.marktouched instead of scmutil.addremove addremove required paths relative to the cwd, which meant a lot of extra code that transformed paths into relative ones. That code is now gone as well.

scmutil: add a function to mark that files have been operated on Several places use scmutil.addremove as a means to declare that certain files have been operated on. This is ugly because: - addremove takes patterns relative to the cwd, not paths relative to the root, which means extra contortions for callers. - addremove doesn't make clear what happens to files whose status hasn't changed. This new method accepts filenames relative to the repo root, and has a much clearer contract. It also allows future modifications that do more with files whose status hasn't changed.

scmutil.addremove: factor out code to mark added/removed/renames An upcoming patch will reuse this code in another function.

scmutil.addremove: factor out code to find renames This code will be used in a different context in upcoming patches.

scmutil.addremove: rename local 'copies' to 'renames' An upcoming patch will refactor some code out into a method called _findrenames. Having a line saying "copies = _findrenames..." is confusing. Besides, 'renames' is a more precise name for this local anyway.

scmutil.addremove: factor out dirstate walk into another function Upcoming patches will reuse and expand on this function for other purposes.

filecontext: use 'is not None' to check for filelog existence Previously we used 'if filelog:' to check if the filelog existed. If the instance did exist, this pattern then calls len() on the filelog to see if it is empty. I'm developing a filelog replacement that doesn't have len() implemented, so it's better to do an explicit 'is not None' check here instead. Also change _changeid() to return the _changeid attribute if it has it. Previously it would try to obtain it from the _changectx(), and if that did not exist it would construct the _changectx() using the linkrev. In the extension I'm working on, filectx's don't have easy access to linkrevs so avoiding this when possible is better.