largefiles: avoid redundant standin() invocations There are some code paths, which apply standin() on same value multilpe times instead of using already standin()-ed value. "fstandin" is common name for "path to standin file" in lfutil.py, to avoid shadowing "standin()".

largefiles: replace hashrepofile by hashfile (API) There is only one user for the former, and repo.wjoin()-ed value is alread known by that user.

largefiles: call readstandin() with changectx itself instead of rev or node readstandin() takes "node" argument to get changectx by "repo[node]". There are some readstandin() invocations, which use ctx.node(), ctx.rev(), or '.' as "node" argument above, even though corresponded changectx object is already looked up on caller side. This patch calls readstandin() with already known changectx itself, to avoid meaningless re-construction of changectx (indirect case via copytostore() is also included). BTW, copytostore() uses "rev" argument only for readstandin() invocation. Therefore, this patch also renames it to "revorctx" to indicate that it can take not only revision ID or so but also changectx, for readability.

largefiles: omit redundant splitstandin() invocations There are 3 splitstandin() invocations in updatestandin() for same "standin" value.

largefiles: replace splitstandin() by isstandin() to omit str creation If splitstandin()-ed str itself isn't used, isstandin() should be used instead of it, to omit meaningless str creation.

largefiles: omit redundant isstandin() before splitstandin() There are many isstandin() invocations before splitstandin(). The former examines whether specified path starts with ".hglf/". The latter returns after ".hglf/" of specified path if it starts with that prefix, or returns None otherwise. Therefore, value returned by splitstandin() can be used for replacement of preceding isstandin(), and this replacement can omit redundant string comparison after isstandin().