Backport of 961f8e99 from master.

Backport of d293d68f from master.

Backport of 8f90593e from master.

Regression in b47552b4.

Backport of 0b98e8fd from master.

Backport of 545dae24 from master

Backport of 413583e2 from master.

Backport of 9a63d840 from master.

Backport of 5a2dd5ec from master

Backport of 7e5cb463 from master

Backport of 084536a9 from master.

Backport of 74ddd0e8 from master

Backport of eb13e6cb from master

Backport of d8f83531 from master.

[2.1.x] Fixed #29890 -- Fixed FileSystemStorage crash if concurrent saves try to create the same directory.

Regression in 632c4ffd.

Backport of 98ef3829 from master.

[2.1.x] Fixed #29896 -- Fixed incorrect Model.save() cache relation clearing for foreign keys that use to_field.

Regression in ee493061.
Backport of f77fc56c from master.

Regression in e1253bc2.
Backport of 9a88c6dd from master.

Backport of 76b33670 from master

Backport of 64174252 from master.

W504 is mutually exclusive with W503 that we follow.

Backport of 58d1e9aa from master.

Backport of 136a900e from master

Backport of b0d716cb from master

Backport of 043407ec from master.

An omission in 388165ad.
Backport of 3deea61f from master

sys.stdin.read() blocks waiting for EOF in shell.py which will
likely never come if the user provides input on stdin via the
keyboard before the shell starts. Added check for a tty to
skip reading stdin if it's not present.

This still allows piping of code into the shell (which should
have no TTY and should have an EOF) but also doesn't cause it
to hang if multi-line input is provided.

Backport of 4e78e389 from master.

Backport of a29fce89 from master.

As of cf546e11, this is the
canonical way to invoke the static tag.
Backport of 084573c7 from master.

Backport of 44f98f78 from master.

Regression in fc6528b2.

Backport of 834c4ec8,
217f82d7, and
dc5e75d4 from master.

Backport of 6752c275 from master.

Backport of 38f3de86 from master.

Backport of f07091a3 from master

Backport of a1ffbfb8 from master

Backport of cecd6561 from master.

Backport of 1b49b792 from master.

Backport of b8b1d8ca from master.

Backport of 82f286cf from master.

Backport of e90af8ba from master.

Support for passing bytestrings to the database API was removed in
301de774.
Backport of f5d9ee11 from master