largefiles: replace invocation of os.path module by vfs in lfcommands.py

cache: rebuild branch cache from scratch when inconsistencies are detected This should recover automatically from some corruptions that for unknown reasons are seen in the wild.

cache: safer handling of failing seek when writing revision branch cache If the seek for some reason fails (perhaps because the file is too short to search to the requested position), make sure we seek to the start and rewrite everything. It is unknown if this fixes a real problem that ever happened.

cache: remove branch revision file before rewriting the branch name file New branch names are usually appended to the branch name file. If that fails or the file has been modified by another process, it is rewritten. That left a small opportunity that there could be references to non-existent entries in the file while it was rewritten. To avoid that, remove the revision branch cache file with the references to the branch name file before rewriting the branch name file. Worst case, when interrupted at the wrong time, the cache will be lost and rebuilt next time. It is unknown if this fixes a real problem that ever happened.

chg: do not redirect stdout to /dev/null Redirecting stdout to /dev/null has unwanted side effects, namely ui.write will stop working. This patch removes the redirection code and helps chg to pass test-bad-extension.t.

pager: skip uisetup if chg is detected chg has its own pager implementation that it wants to skip pager's uisetup. It is currently done by redirecting stdout to /dev/null, which has unintended side effects. This patch makes pager aware of chg and skip uisetup directly from pager. We may want to merge chg and pager's pager implementation to make this unnecessary in the future.

chgserver: add an explicit gc to trigger __del__ SocketServer.ForkingMixIn uses os._exit which will skip all cleanup handlers. We want to run __del__ to make things like transactions, {ssh,http}peer, atomictempfile, dirstateguard, etc. work. This patch adds a "gc.collect()" to trigger __del__. It is helpful for chg to pass some test cases in test-devel-warnings.t.