subrepo: replace direct file APIs around "readlines" by "vfs.tryreadlines" This patch also replaces "self._getstorehashcachepath" (building absolute path up) by "self._getstorehashcachename" (building relative path up), because "vfs.tryreadlines" requires relative path. This patch makes "_readstorehashcache()" return "[]" (returned by "vfs.tryreadlines()"), when cache file doesn't exist, even though "_readstorehashcache()" returned '' (empty string) in such case before this patch. "_readstorehashcache()" is invoked only by the code path below in "_storeclean()": for filehash in self._readstorehashcache(path): if filehash != itercache.next(): clean = False break In this case, "[]" and '' don't differ from each other, because both of them cause avoiding iteration of "for loop".

vfs: add "readlines" and "tryreadlines" This patch allows "readlines" and "tryreadlines" to take "mode" argument, because "subrepo" requires to read files not in "rb" (binary, default for vfs) but in "r" (text) mode in subsequent patch.

subrepo: add "_cachestorehashvfs" to handle cache store hash files via vfs This "vfs" object will be used by subsequent patches to handle cache store hash files without direct file APIs. This patch decorates "_cachestorehashvfs" with "@propertycache" to delay vfs creation, because it is used only for cooperation with other repositories. In this patch, "/" is used as the path separator, even though "self._repo.join" uses platform specific path separator (e.g. "\\" on Windows). But it is reasonable enough, because "store" and other management file handling already include such implementation, and they work well.