Git - v2.37.4

This primarily is to backport various fixes accumulated on the 'master'
front since 2.37.3, and also includes the same security fixes as in
v2.30.6.

Fixes since v2.37.3

• CVE-2022-39253:
  When relying on the --local clone optimization, Git dereferences
  symbolic links in the source repository before creating hardlinks
  (or copies) of the dereferenced link in the destination repository.
  This can lead to surprising behavior where arbitrary files are
  present in a repository's $GIT_DIR when cloning from a malicious
  repository.

Git will no longer dereference symbolic links via the --local
clone mechanism, and will instead refuse to clone repositories that
have symbolic links present in the $GIT_DIR/objects directory.

Additionally, the value of protocol.file.allow is changed to be
"user" by default.

Credit for finding CVE-2022-39253 goes to Cory Snider of Mirantis.
The fix was authored by Taylor Blau, with help from Johannes
Schindelin.

• CVE-2022-39260:
  An overly-long command string given to git shell can result in
  overflow in split_cmdline(), leading to arbitrary heap writes and
  remote code execution when git shell is exposed and the directory
  $HOME/git-shell-commands exists.

git shell is taught to refuse interactive commands that are
longer than 4MiB in size. split_cmdline() is hardened to reject
inputs larger than 2GiB.

Credit for finding CVE-2022-39260 goes to Kevin Backhouse of
GitHub. The fix was authored by Kevin Backhouse, Jeff King, and
Taylor Blau.

• An earlier optimization discarded a tree-object buffer that is
  still in use, which has been corrected.

• Fix deadlocks between main Git process and subprocess spawned via
  the pipe_command() API, that can kill "git add -p" that was
  reimplemented in C recently.

• xcalloc(), imitating calloc(), takes "number of elements of the
  array", and "size of a single element", in this order. A call that
  does not follow this ordering has been corrected.

• The preload-index codepath made copies of pathspec to give to
  multiple threads, which were left leaked.

• Update the version of Ubuntu used for GitHub Actions CI from 18.04
  to 22.04.

• The auto-stashed local changes created by "git merge --autostash"
  was mixed into a conflicted state left in the working tree, which
  has been corrected.

Also contains other minor documentation updates and code clean-ups.