When the index is locked and child processes inherit the handle to
said lock and the parent process wants to remove the lock before the
child process exits, on Windows there is a problem: it won't work
because files cannot be deleted if a process holds a handle on them.
The symptom:
Rename from 'xxx/.git/index.lock' to 'xxx/.git/index' failed.
Should I try again? (y/n)
Spawning child processes with bInheritHandles==FALSE would not work
because no file handles would be inherited, not even the hStdXxx
handles in STARTUPINFO (stdin/stdout/stderr).
Opening every file with O_NOINHERIT does not work, either, as e.g.
git-upload-pack expects inherited file handles.
This leaves us with the only way out: creating temp files with the
O_NOINHERIT flag. This flag is Windows-specific, however. For our
purposes, it is equivalent to O_CLOEXEC (which does not exist on
Windows), so let's just open temporary files with the O_CLOEXEC flag and
map that flag to O_NOINHERIT on Windows.
As Eric Wong pointed out, we need to be careful to handle the case where
the Linux headers used to compile Git support O_CLOEXEC but the Linux
kernel used to run Git does not: it returns an EINVAL.
This fixes the test that we just introduced to demonstrate the problem.
Signed-off-by: Ben Wijen <ben@wijen.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
On Windows, a file cannot be removed unless all file handles to it have
been released. Hence it is particularly important to close handles when
spawning children (which would probably not even know that they hold on
to those handles).
The example chosen for this test is a custom merge driver that indeed
has no idea that it blocks the deletion of index.lock. The full use case
is a daemon that lives on after the merge, with subsequent invocations
handing off to the daemon, thereby avoiding hefty start-up costs. We
simulate this behavior by simply sleeping one second.
Note that the test only fails on Windows, due to the file locking issue.
Since we have no way to say "expect failure with MINGW, success
otherwise", we simply skip this test on Windows for now.
Signed-off-by: Ben Wijen <ben@wijen.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
While it makes sense to allow merging unrelated histories of two
projects that started independently into one, in the way "gitk" was
merged to "git" itself aka "the coolest merge ever", such a merge is
still an unusual event. Worse, if somebody creates an independent
history by starting from a tarball of an established project and
sends a pull request to the original project, "git merge" however
happily creates such a merge without any sign of something unusual
is happening.
Teach "git merge" to refuse to create such a merge by default,
unless the user passes a new "--allow-unrelated-histories" option to
tell it that the user is aware that two unrelated projects are
merged.
Because such a "two project merge" is a rare event, a configuration
option to always allow such a merge is not added.
We could add the same option to "git pull" and have it passed
through to underlying "git merge". I do not have a fundamental
opposition against such a feature, but this commit does not do so
and instead leaves it as low-hanging fruit for others, because such
a "two project merge" would be done after fetching the other project
into some location in the working tree of an existing project and
making sure how well they fit together, it is sufficient to allow a
local merge without such an option pass-through from "git pull" to
"git merge". Many tests that are updated by this patch does the
pass-through manually by turning:
git pull something
into its equivalent:
git fetch something &&
git merge --allow-unrelated-histories FETCH_HEAD
If somebody is inclined to add such an option, updated tests in this
change need to be adjusted back to:
git pull --allow-unrelated-histories something
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Traditionally, external low-level 3-way merge drivers are expected
to produce their results based solely on the contents of the three
variants given in temporary files named by %O, %A and %B on their
command line. Additionally allow them to look at the final path
(given by %P).
* jc/ll-merge-expose-path:
ll-merge: pass the original path to external drivers
The interface to custom low-level merge driver was modeled to be
capable of driving programs like "merge" (from the RCS suite) that
can produce result solely by looking at three files that hold
contents of common ancestor, ours and theirs. The information we
feed to the external drivers via the command line placeholders %O,
%A, and %B were designed to be purely about contents by giving
names of the temporary files that hold these variants without
exposing the original pathname. No matter where the result goes,
merging the same three variants should produce the same result,
contents is the king, that is the Git way.
The external driver interface, however, is meant to help people to
step outside the Git worldview, and sometimes people want to know
the final path that the resulting merged contents would be stored
in. Expose this to the external drivers via a new placeholder %P.
Requested-by: Andreas Gondek
Signed-off-by: Junio C Hamano <gitster@pobox.com>
These are all cases where we do a setup step of the form:
for i in $foo; do
set_up $i || break
done &&
more_setup
would not notice a failure in set_up (because break always
returns a 0 exit code). These are just setup steps that we
do not expect to fail, but it does not hurt to be defensive.
Most can be fixed by converting the "break" to a "return 1"
(since we eval our tests inside a function for just this
purpose). A few of the loops are inside subshells, so we can
use just "exit 1" to break out of the subshell. And a few
can actually be made shorter by just unrolling the loop.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* mv/merge-recursive:
builtin-merge: release the lockfile in try_merge_strategy()
merge-recursive: get rid of virtual_id
merge-recursive: move current_{file,directory}_set to struct merge_options
merge-recursive: move the global obuf to struct merge_options
merge-recursive: get rid of the index_only global variable
merge-recursive: move call_depth to struct merge_options
cherry-pick/revert: make direct internal call to merge_tree()
builtin-merge: avoid run_command_v_opt() for recursive and subtree
merge-recursive: introduce merge_options
merge-recursive.c: Add more generic merge_recursive_generic()
Split out merge_recursive() to merge-recursive.c
Once we committed the locked index, we should release the lockfile. In
most cases this is done automatically when the process ends, but this is
not true in this case.
[jc: with additional tests from Eric Raible]
Signed-off-by: Miklos Vajna <vmiklos@frugalware.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This changes the configuration syntax for defining a low-level
merge driver to be:
[merge "<<drivername>>"]
driver = "<<command line>>"
name = "<<driver description>>"
which is much nicer to read and is extensible. Credit goes to
Martin Waitz and Linus.
In addition, when we use an external low-level merge driver, it
is reported as an extra output from merge-recursive, using the
value of merge.<<drivername>.name variable.
The demonstration in t6026 has also been updated.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This allows users to specify custom low-level merge driver per
path, using the attributes mechanism. Just like you can specify
one of built-in "text", "binary", "union" low-level merge
drivers by saying:
* merge=text
.gitignore merge=union
*.jpg merge=binary
pick a name of your favorite merge driver, and assign it as the
value of the 'merge' attribute.
A custom low-level merge driver is defined via the config
mechanism. This patch introduces 'merge.driver', a multi-valued
configuration. Its value is the name (i.e. the one you use as
the value of 'merge' attribute) followed by a command line
specification. The command line can contain %O, %A, and %B to
be interpolated with the names of temporary files that hold the
common ancestor version, the version from your branch, and the
version from the other branch, and the resulting command is
spawned.
The low-level merge driver is expected to update the temporary
file for your branch (i.e. %A) with the result and exit with
status 0 for a clean merge, and non-zero status for a conflicted
merge.
A new test in t6026 demonstrates a sample usage.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This demonstrates how the new low-level per-path merge backends,
union and ours, work, and shows how they are controlled by the
gitattribute mechanism.
Signed-off-by: Junio C Hamano <junkio@cox.net>
