The submodule code has been taught to work better with separate
work trees created via "git worktree add".

* mk/submodule-gitdir-path:
  path: implement common_dir handling in git_pathdup_submodule()
  submodule refactor: use strbuf_git_path_submodule() in add_submodule_odb()

Prepare for Git on-disk repository representation to undergo
backward incompatible changes by introducing a new repository
format version "1", with an extension mechanism.

* jk/repository-extension:
  introduce "preciousObjects" repository extension
  introduce "extensions" form of core.repositoryformatversion

When submodule is a linked worktree, "git diff --submodule" and other
calls which directly access the submodule's object database do not correctly
calculate its path. Fix it by changing the git_pathdup_submodule() behavior,
to use either common or per-worktree directory.

Do it similarly as for parent repository, but ignore the GIT_COMMON_DIR
environment variable, because it would mean common directory for the parent
repository and does not make sense for submodule.

Also add test for functionality which uses this call.

Signed-off-by: Max Kirillov <max@max630.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

The code in "multiple-worktree" support that attempted to recover
from an inconsistent state updated an incorrect file.

* nd/fixup-linked-gitdir:
  setup: update the right file in multiple checkouts

All of the callsites covered by this change call write_file() or
write_file_gently() to create a one-liner file.  Drop the caller
supplied LF and let these callees to append it as necessary.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

This code is introduced in 23af91d (prune: strategies for linked
checkouts - 2014-11-30), and it's supposed to implement this rule from
that commit's message:

 - linked checkouts are supposed to keep its location in $R/gitdir up
   to date. The use case is auto fixup after a manual checkout move.

Note the name, "$R/gitdir", not "$R/gitfile". Correct the path to be
updated accordingly.

While at there, make sure I/O errors are not silently dropped.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

All callers except three passed 1 for the "fatal" parameter to ask
this function to die upon error, but to a casual reader of the code,
it was not all obvious what that 1 meant.  Instead, split the
function into two based on a common write_file_v() that takes the
flag, introduce write_file_gently() as a new way to attempt creating
a file without dying on error, and make three callers to call it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Replace "is this subdirectory a separate repository that should not
be touched?" check "git clean" does by checking if it has .git/HEAD
using the submodule-related code with a more optimized check.

* ee/clean-remove-dirs:
  read_gitfile_gently: fix use-after-free
  clean: improve performance when removing lots of directories
  p7300: add performance tests for clean
  t7300: add tests to document behavior of clean and nested git
  setup: sanity check file size in read_gitfile_gently
  setup: add gentle version of read_gitfile

The "dir" variable is a pointer into the "buf" array. When
we hit the cleanup_return path, the first thing we do is
free(buf); but one of the error messages prints "dir", which
will access the memory after the free.

We can fix this by reorganizing the error path a little. We
act on the fatal, error-printing conditions first, as they
want to access memory and do not care about freeing. Then we
free any memory, and finally return.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

If this extension is used in a repository, then no
operations should run which may drop objects from the object
storage. This can be useful if you are sharing that storage
with other repositories whose refs you cannot see.

For instance, if you do:

  $ git clone -s parent child
  $ git -C parent config extensions.preciousObjects true
  $ git -C parent config core.repositoryformatversion 1

you now have additional safety when running git in the
parent repository. Prunes and repacks will bail with an
error, and `git gc` will skip those operations (it will
continue to pack refs and do other non-object operations).
Older versions of git, when run in the repository, will
fail on every operation.

Note that we do not set the preciousObjects extension by
default when doing a "clone -s", as doing so breaks
backwards compatibility. It is a decision the user should
make explicitly.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>