branching: merge stable into default

lfs: fix interpolation of int and %s in an exception case Seen in the wild in a server log when MS antivirus was quarantining a file on the client side.

tests: catch "Can't assign requested address" in test-https.t (issue6726)

tests: add another variation of EADDRNOTAVAIL message (e.g. from NetBSD)

configitems: change the `verify.skipflags` default value to avoid a py3 crash The revlog and LFS modules use various `&` and `&=` operations with this value, which no longer treats `None` as 0. Since nothing cares if it was actually set in the config or not, just default to 0 for simplicity.

windows: gracefully handle when the username cannot be determined This assumes implementation details, but I don't see any other way than to check the environment variables ourselves (which would miss out on any future enhancements that Python may make). This was originally reported as https://foss.heptapod.net/mercurial/tortoisehg/thg/-/issues/5835.

shelve: do not add the dirstate backup to the transaction Otherwise the transaction will properly clean up its mess on abort… deleting the backup in the process. This break with dirstate-v2 that has more file than just the dirstate. The dirstate itself is full of various exception and is "fine" when using dirstate-v1.