* maint-2.32:
Git 2.32.3
Git 2.31.4
Git 2.30.5
setup: tighten ownership checks post CVE-2022-24765
git-compat-util: allow root to access both SUDO_UID and root owned
t0034: add negative tests and allow git init to mostly work under sudo
git-compat-util: avoid failing dir ownership checks if running privileged
t: regression git needs safe.directory when using sudo
* maint-2.31:
Git 2.31.4
Git 2.30.5
setup: tighten ownership checks post CVE-2022-24765
git-compat-util: allow root to access both SUDO_UID and root owned
t0034: add negative tests and allow git init to mostly work under sudo
git-compat-util: avoid failing dir ownership checks if running privileged
t: regression git needs safe.directory when using sudo
* maint-2.30:
Git 2.30.5
setup: tighten ownership checks post CVE-2022-24765
git-compat-util: allow root to access both SUDO_UID and root owned
t0034: add negative tests and allow git init to mostly work under sudo
git-compat-util: avoid failing dir ownership checks if running privileged
t: regression git needs safe.directory when using sudo
setup: tighten ownership checks post CVE-2022-24765
8959555cee7 (setup_git_directory(): add an owner check for the top-level
directory, 2022-03-02), adds a function to check for ownership of
repositories using a directory that is representative of it, and ways to
add exempt a specific repository from said check if needed, but that
check didn't account for owership of the gitdir, or (when used) the
gitfile that points to that gitdir.
An attacker could create a git repository in a directory that they can
write into but that is owned by the victim to work around the fix that
was introduced with CVE-2022-24765 to potentially run code as the
victim.
An example that could result in privilege escalation to root in *NIX would
be to set a repository in a shared tmp directory by doing (for example):
$ git -C /tmp init
To avoid that, extend the ensure_valid_ownership function to be able to
check for all three paths.
This will have the side effect of tripling the number of stat() calls
when a repository is detected, but the effect is expected to be likely
minimal, as it is done only once during the directory walk in which Git
looks for a repository.
Additionally make sure to resolve the gitfile (if one was used) to find
the relevant gitdir for checking.
While at it change the message printed on failure so it is clear we are
referring to the repository by its worktree (or gitdir if it is bare) and
not to a specific directory.
Helped-by: Junio C Hamano <junio@pobox.com> Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Junio C Hamano [Thu, 26 May 2022 21:51:32 +0000 (14:51 -0700)]
Merge branch 'cb/path-owner-check-with-sudo'
With a recent update to refuse access to repositories of other
people by default, "sudo make install" and "sudo git describe"
stopped working. This series intends to loosen it while keeping
the safety.
* cb/path-owner-check-with-sudo:
t0034: add negative tests and allow git init to mostly work under sudo
git-compat-util: avoid failing dir ownership checks if running privileged
t: regression git needs safe.directory when using sudo
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
git-compat-util: allow root to access both SUDO_UID and root owned
Previous changes introduced a regression which will prevent root for
accessing repositories owned by thyself if using sudo because SUDO_UID
takes precedence.
Loosen that restriction by allowing root to access repositories owned
by both uid by default and without having to add a safe.directory
exception.
A previous workaround that was documented in the tests is no longer
needed so it has been removed together with its specially crafted
prerequisite.
Helped-by: Johanness Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
t0034: add negative tests and allow git init to mostly work under sudo
Add a support library that provides one function that can be used
to run a "scriplet" of commands through sudo and that helps invoking
sudo in the slightly awkward way that is required to ensure it doesn't
block the call (if shell was allowed as tested in the prerequisite)
and it doesn't run the command through a different shell than the one
we intended.
Add additional negative tests as suggested by Junio and that use a
new workspace that is owned by root.
Document a regression that was introduced by previous commits where
root won't be able anymore to access directories they own unless
SUDO_UID is removed from their environment.
The tests document additional ways that this new restriction could
be worked around and the documentation explains why it might be instead
considered a feature, but a "fix" is planned for a future change.
Helped-by: Junio C Hamano <gitster@pobox.com> Helped-by: Phillip Wood <phillip.wood123@gmail.com> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
git-compat-util: avoid failing dir ownership checks if running privileged
bdc77d1d685 (Add a function to determine whether a path is owned by the
current user, 2022-03-02) checks for the effective uid of the running
process using geteuid() but didn't account for cases where that user was
root (because git was invoked through sudo or a compatible tool) and the
original uid that repository trusted for its config was no longer known,
therefore failing the following otherwise safe call:
guy@renard ~/Software/uncrustify $ sudo git describe --always --dirty
[sudo] password for guy:
fatal: unsafe repository ('/home/guy/Software/uncrustify' is owned by someone else)
Attempt to detect those cases by using the environment variables that
those tools create to keep track of the original user id, and do the
ownership check using that instead.
This assumes the environment the user is running on after going
privileged can't be tampered with, and also adds code to restrict that
the new behavior only applies if running as root, therefore keeping the
most common case, which runs unprivileged, from changing, but because of
that, it will miss cases where sudo (or an equivalent) was used to change
to another unprivileged user or where the equivalent tool used to raise
privileges didn't track the original id in a sudo compatible way.
Because of compatibility with sudo, the code assumes that uid_t is an
unsigned integer type (which is not required by the standard) but is used
that way in their codebase to generate SUDO_UID. In systems where uid_t
is signed, sudo might be also patched to NOT be unsigned and that might
be able to trigger an edge case and a bug (as described in the code), but
it is considered unlikely to happen and even if it does, the code would
just mostly fail safely, so there was no attempt either to detect it or
prevent it by the code, which is something that might change in the future,
based on expected user feedback.
Reported-by: Guy Maurel <guy.j@maurel.de> Helped-by: SZEDER Gábor <szeder.dev@gmail.com> Helped-by: Randall Becker <rsbecker@nexbridge.com> Helped-by: Phillip Wood <phillip.wood123@gmail.com> Suggested-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
t: regression git needs safe.directory when using sudo
Originally reported after release of v2.35.2 (and other maint branches)
for CVE-2022-24765 and blocking otherwise harmless commands that were
done using sudo in a repository that was owned by the user.
Add a new test script with very basic support to allow running git
commands through sudo, so a reproduction could be implemented and that
uses only `git status` as a proxy of the issue reported.
Note that because of the way sudo interacts with the system, a much
more complete integration with the test framework will require a lot
more work and that was therefore intentionally punted for now.
The current implementation requires the execution of a special cleanup
function which should always be kept as the last "test" or otherwise
the standard cleanup functions will fail because they can't remove
the root owned directories that are used. This also means that if
failures are found while running, the specifics of the failure might
not be kept for further debugging and if the test was interrupted, it
will be necessary to clean the working directory manually before
restarting by running:
The test file also uses at least one initial "setup" test that creates
a parallel execution directory under the "root" sub directory, which
should be used as top level directory for all repositories that are
used in this test file. Unlike all other tests the repository provided
by the test framework should go unused.
Special care should be taken when invoking commands through sudo, since
the environment is otherwise independent from what the test framework
setup and might have changed the values for HOME, SHELL and dropped
several relevant environment variables for your test. Indeed `git status`
was used as a proxy because it doesn't even require commits in the
repository to work and usually doesn't require much from the environment
to run, but a future patch will add calls to `git init` and that will
fail to honor the default branch name, unless that setting is NOT
provided through an environment variable (which means even a CI run
could fail that test if enabled incorrectly).
A new SUDO prerequisite is provided that does some sanity checking
to make sure the sudo command that will be used allows for passwordless
execution as root without restrictions and doesn't mess with git's
execution path. This matches what is provided by the macOS agents that
are used as part of GitHub actions and probably nowhere else.
Most of those characteristics make this test mostly only suitable for
CI, but it might be executed locally if special care is taken to provide
for all of them in the local configuration and maybe making use of the
sudo credential cache by first invoking sudo, entering your password if
needed, and then invoking the test with:
If it fails to run, then it means your local setup wouldn't work for the
test because of the configuration sudo has or other system settings, and
things that might help are to comment out sudo's secure_path config, and
make sure that the account you are using has no restrictions on the
commands it can run through sudo, just like is provided for the user in
the CI.
For example (assuming a username of marta for you) something probably
similar to the following entry in your /etc/sudoers (or equivalent) file:
marta ALL=(ALL:ALL) NOPASSWD: ALL
Reported-by: SZEDER Gábor <szeder.dev@gmail.com> Helped-by: Phillip Wood <phillip.wood123@gmail.com> Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
With the addition of the safe.directory in 8959555ce
(setup_git_directory(): add an owner check for the top-level directory,
2022-03-02) released in v2.35.2, we are receiving feedback from a
variety of users about the feature.
Some users have a very large list of shared repositories and find it
cumbersome to add this config for every one of them.
In a more difficult case, certain workflows involve running Git commands
within containers. The container boundary prevents any global or system
config from communicating `safe.directory` values from the host into the
container. Further, the container almost always runs as a different user
than the owner of the directory in the host.
To simplify the reactions necessary for these users, extend the
definition of the safe.directory config value to include a possible '*'
value. This value implies that all directories are safe, providing a
single setting to opt-out of this protection.
Note that an empty assignment of safe.directory clears all previous
values, and this is already the case with the "if (!value || !*value)"
condition.
Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
It seems that nothing is ever checking to make sure the safe directories
in the configs actually have the key safe.directory, so some unrelated
config that has a value with a certain directory would also make it a
safe directory.
Signed-off-by: Matheus Valadares <me@m28.io> Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
It is difficult to change the ownership on a directory in our test
suite, so insert a new GIT_TEST_ASSUME_DIFFERENT_OWNER environment
variable to trick Git into thinking we are in a differently-owned
directory. This allows us to test that the config is parsed correctly.
Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
* maint-2.32:
Git 2.32.1
Git 2.31.2
Git 2.30.3
setup_git_directory(): add an owner check for the top-level directory
Add a function to determine whether a path is owned by the current user
* maint-2.31:
Git 2.31.2
Git 2.30.3
setup_git_directory(): add an owner check for the top-level directory
Add a function to determine whether a path is owned by the current user
* maint-2.30:
Git 2.30.3
setup_git_directory(): add an owner check for the top-level directory
Add a function to determine whether a path is owned by the current user
Fix `GIT_CEILING_DIRECTORIES` with `C:\` and the likes
When determining the length of the longest ancestor of a given path with
respect to to e.g. `GIT_CEILING_DIRECTORIES`, we special-case the root
directory by returning 0 (i.e. we pretend that the path `/` does not end
in a slash by virtually stripping it).
That is the correct behavior because when normalizing paths, the root
directory is special: all other directory paths have their trailing
slash stripped, but not the root directory's path (because it would
become the empty string, which is not a legal path).
However, this special-casing of the root directory in
`longest_ancestor_length()` completely forgets about Windows-style root
directories, e.g. `C:\`. These _also_ get normalized with a trailing
slash (because `C:` would actually refer to the current directory on
that drive, not necessarily to its root directory).
In fc56c7b34b (mingw: accomodate t0060-path-utils for MSYS2,
2016-01-27), we almost got it right. We noticed that
`longest_ancestor_length()` expects a slash _after_ the matched prefix,
and if the prefix already ends in a slash, the normalized path won't
ever match and -1 is returned.
But then that commit went astray: The correct fix is not to adjust the
_tests_ to expect an incorrect -1 when that function is fed a prefix
that ends in a slash, but instead to treat such a prefix as if the
trailing slash had been removed.
Likewise, that function needs to handle the case where it is fed a path
that ends in a slash (not only a prefix that ends in a slash): if it
matches the prefix (plus trailing slash), we still need to verify that
the path does not end there, otherwise the prefix is not actually an
ancestor of the path but identical to it (and we need to return -1 in
that case).
With these two adjustments, we no longer need to play games in t0060
where we only add `$rootoff` if the passed prefix is different from the
MSYS2 pseudo root, instead we also add it for the MSYS2 pseudo root
itself. We do have to be careful to skip that logic entirely for Windows
paths, though, because they do are not subject to that MSYS2 pseudo root
treatment.
This patch fixes the scenario where a user has set
`GIT_CEILING_DIRECTORIES=C:\`, which would be ignored otherwise.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
setup_git_directory(): add an owner check for the top-level directory
It poses a security risk to search for a git directory outside of the
directories owned by the current user.
For example, it is common e.g. in computer pools of educational
institutes to have a "scratch" space: a mounted disk with plenty of
space that is regularly swiped where any authenticated user can create
a directory to do their work. Merely navigating to such a space with a
Git-enabled `PS1` when there is a maliciously-crafted `/scratch/.git/`
can lead to a compromised account.
The same holds true in multi-user setups running Windows, as `C:\` is
writable to every authenticated user by default.
To plug this vulnerability, we stop Git from accepting top-level
directories owned by someone other than the current user. We avoid
looking at the ownership of each and every directories between the
current and the top-level one (if there are any between) to avoid
introducing a performance bottleneck.
This new default behavior is obviously incompatible with the concept of
shared repositories, where we expect the top-level directory to be owned
by only one of its legitimate users. To re-enable that use case, we add
support for adding exceptions from the new default behavior via the
config setting `safe.directory`.
The `safe.directory` config setting is only respected in the system and
global configs, not from repository configs or via the command-line, and
can have multiple values to allow for multiple shared repositories.
We are particularly careful to provide a helpful message to any user
trying to use a shared repository.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Add a function to determine whether a path is owned by the current user
This function will be used in the next commit to prevent
`setup_git_directory()` from discovering a repository in a directory
that is owned by someone other than the current user.
Note: We cannot simply use `st.st_uid` on Windows just like we do on
Linux and other Unix-like platforms: according to
https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/stat-functions
this field is always zero on Windows (because Windows' idea of a user ID
does not fit into a single numerical value). Therefore, we have to do
something a little involved to replicate the same functionality there.
Also note: On Windows, a user's home directory is not actually owned by
said user, but by the administrator. For all practical purposes, it is
under the user's control, though, therefore we pretend that it is owned
by the user.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
mingw-w64's pthread_unistd.h had a bug that mistakenly (because there is
no support for the *lockfile() functions required[1]) defined
_POSIX_THREAD_SAFE_FUNCTIONS and that was being worked around since 3ecd153a3b (compat/mingw: support MSys2-based MinGW build, 2016-01-14).
The bug was fixed in winphtreads, but as a side effect, leaves the
reentrant functions from time.h no longer visible and therefore breaks
the build.
Since the intention all along was to avoid using the fallback functions,
formalize the use of POSIX by setting the corresponding feature flag and
compile out the implementation for the fallback functions.
[1] https://unix.org/whitepapers/reentrant.html
Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com> Acked-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Victoria Dye [Thu, 4 Nov 2021 04:01:03 +0000 (04:01 +0000)]
async_die_is_recursing: work around GCC v11.x issue on Fedora
This fix corrects an issue found in the `dockerized(pedantic, fedora)` CI
build, first appearing after the introduction of a new version of the Fedora
docker image version. This image includes a version of `glibc` with the
attribute `__attr_access_none` added to `pthread_setspecific` [1], the
implementation of which only exists for GCC 11.X - the version included in
the Fedora image. The attribute requires that the pointer provided in the
second argument of `pthread_getspecific` must, if not NULL, be a pointer to
a valid object. In the usage in `async_die_is_recursing`, `(void *)1` is not
valid, causing the error.
This fix imitates a workaround added in SELinux [2] by using the pointer to
the static `async_die_counter` itself as the second argument to
`pthread_setspecific`. This guaranteed non-NULL, valid pointer matches the
intent of the current usage while not triggering the build error.
Co-authored-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Victoria Dye <vdye@github.com> Acked-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Phillip Wood [Tue, 2 Nov 2021 21:30:51 +0000 (21:30 +0000)]
rebase -i: fix rewording with --committer-date-is-author-date
baf8ec8d3a (rebase -r: don't write .git/MERGE_MSG when
fast-forwarding, 2021-08-20) stopped reading the author script in
run_git_commit() when rewording a commit. This is normally safe
because "git commit --amend" preserves the authorship. However if the
user passes "--committer-date-is-author-date" then we need to read the
author date from the author script when rewording. Fix this regression
by tightening the check for when it is safe to skip reading the author
script.
Reported-by: Jonas Kittner <jonas.kittner@ruhr-uni-bochum.de> Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Jeff King [Fri, 29 Oct 2021 21:10:03 +0000 (17:10 -0400)]
log: document --encoding behavior on iconv() failure
We already note that we may produce invalid output when we skip calling
iconv() altogether. But we may also do so if iconv() fails, and we have
no good alternative. Let's document this to avoid surprising users.
Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Junio C Hamano [Fri, 29 Oct 2021 20:48:58 +0000 (13:48 -0700)]
Revert "logmsg_reencode(): warn when iconv() fails"
This reverts commit fd680bc5 (logmsg_reencode(): warn when iconv()
fails, 2021-08-27). Throwing a warning for each and every commit
that gets reencoded, without allowing a way to squelch, would make
it unpleasant for folks who have to deal with an ancient part of the
history in an old project that used wrong encoding in the commits.
Junio C Hamano [Tue, 12 Oct 2021 20:51:48 +0000 (13:51 -0700)]
Merge branch 'cb/cvsserver' into maint
"git cvsserver" had a long-standing bug in its authentication code,
which has finally been corrected (it is unclear and is a separate
question if anybody is seriously using it, though).
* cb/cvsserver:
Documentation: cleanup git-cvsserver
git-cvsserver: protect against NULL in crypt(3)
git-cvsserver: use crypt correctly to compare password hashes
Junio C Hamano [Tue, 12 Oct 2021 20:51:46 +0000 (13:51 -0700)]
Merge branch 'rs/no-mode-to-open-when-appending' into maint
The "mode" word is useless in a call to open(2) that does not
create a new file. Such a call in the files backend of the ref
subsystem has been cleaned up.
* rs/no-mode-to-open-when-appending:
refs/files-backend: remove unused open mode parameter
Junio C Hamano [Tue, 12 Oct 2021 20:51:45 +0000 (13:51 -0700)]
Merge branch 'tb/pack-finalize-ordering' into maint
The order in which various files that make up a single (conceptual)
packfile has been reevaluated and straightened up. This matters in
correctness, as an incomplete set of files must not be shown to a
running Git.
* tb/pack-finalize-ordering:
pack-objects: rename .idx files into place after .bitmap files
pack-write: split up finish_tmp_packfile() function
builtin/index-pack.c: move `.idx` files into place last
index-pack: refactor renaming in final()
builtin/repack.c: move `.idx` files into place last
pack-write.c: rename `.idx` files after `*.rev`
pack-write: refactor renaming in finish_tmp_packfile()
bulk-checkin.c: store checksum directly
pack.h: line-wrap the definition of finish_tmp_packfile()
Junio C Hamano [Tue, 12 Oct 2021 20:51:44 +0000 (13:51 -0700)]
Merge branch 'jc/trivial-threeway-binary-merge' into maint
The "git apply -3" code path learned not to bother the lower level
merge machinery when the three-way merge can be trivially resolved
without the content level merge.
* jc/trivial-threeway-binary-merge:
apply: resolve trivial merge without hitting ll-merge with "--3way"
Junio C Hamano [Tue, 12 Oct 2021 20:51:43 +0000 (13:51 -0700)]
Merge branch 'mh/send-email-reset-in-reply-to' into maint
Even when running "git send-email" without its own threaded
discussion support, a threading related header in one message is
carried over to the subsequent message to result in an unwanted
threading, which has been corrected.
Junio C Hamano [Tue, 12 Oct 2021 20:51:42 +0000 (13:51 -0700)]
Merge branch 'sg/set-ceiling-during-tests' into maint
Buggy tests could damage repositories outside the throw-away test
area we created. We now by default export GIT_CEILING_DIRECTORIES
to limit the damage from such a stray test.
* sg/set-ceiling-during-tests:
test-lib: set GIT_CEILING_DIRECTORIES to protect the surrounding repository
Junio C Hamano [Tue, 12 Oct 2021 20:51:41 +0000 (13:51 -0700)]
Merge branch 'cb/makefile-apple-clang' into maint
Build update for Apple clang.
* cb/makefile-apple-clang:
build: catch clang that identifies itself as "$VENDOR clang"
build: clang version may not be followed by extra words
build: update detect-compiler for newer Xcode version
Junio C Hamano [Tue, 12 Oct 2021 20:51:39 +0000 (13:51 -0700)]
Merge branch 'pw/rebase-r-fixes' into maint
Various bugs in "git rebase -r" have been fixed.
* pw/rebase-r-fixes:
rebase -r: fix merge -c with a merge strategy
rebase -r: don't write .git/MERGE_MSG when fast-forwarding
rebase -i: add another reword test
rebase -r: make 'merge -c' behave like reword
Junio C Hamano [Tue, 12 Oct 2021 20:51:39 +0000 (13:51 -0700)]
Merge branch 'pw/rebase-skip-final-fix' into maint
Checking out all the paths from HEAD during the last conflicted
step in "git rebase" and continuing would cause the step to be
skipped (which is expected), but leaves MERGE_MSG file behind in
$GIT_DIR and confuses the next "git commit", which has been
corrected.
* pw/rebase-skip-final-fix:
rebase --continue: remove .git/MERGE_MSG
rebase --apply: restore some tests
t3403: fix commit authorship
Junio C Hamano [Tue, 12 Oct 2021 20:51:38 +0000 (13:51 -0700)]
Merge branch 'jk/range-diff-fixes' into maint
"git range-diff" code clean-up.
* jk/range-diff-fixes:
range-diff: use ssize_t for parsed "len" in read_patches()
range-diff: handle unterminated lines in read_patches()
range-diff: drop useless "offset" variable from read_patches()
Junio C Hamano [Tue, 12 Oct 2021 20:51:36 +0000 (13:51 -0700)]
Merge branch 'en/pull-conflicting-options' into maint
"git pull" had various corner cases that were not well thought out
around its --rebase backend, e.g. "git pull --ff-only" did not stop
but went ahead and rebased when the history on other side is not a
descendant of our history. The series tries to fix them up.
* en/pull-conflicting-options:
pull: fix handling of multiple heads
pull: update docs & code for option compatibility with rebasing
pull: abort by default when fast-forwarding is not possible
pull: make --rebase and --no-rebase override pull.ff=only
pull: since --ff-only overrides, handle it first
pull: abort if --ff-only is given and fast-forwarding is impossible
t7601: add tests of interactions with multiple merge heads and config
t7601: test interaction of merge/rebase/fast-forward flags and options
Junio C Hamano [Tue, 12 Oct 2021 20:51:36 +0000 (13:51 -0700)]
Merge branch 'jt/push-negotiation-fixes' into maint
Bugfix for common ancestor negotiation recently introduced in "git
push" codepath.
* jt/push-negotiation-fixes:
fetch: die on invalid --negotiation-tip hash
send-pack: fix push nego. when remote has refs
send-pack: fix push.negotiate with remote helper