When "git merge" detects a path that is renamed in one history
while the other history deleted (or modified) it, it now reports
both paths to help the user understand what is going on in the two
histories being merged.
* mm/merge-rename-delete-message:
merge-recursive: make "CONFLICT (rename/delete)" message show both paths
Apply the semantic patch swap.cocci to convert hand-rolled swaps to use
the macro SWAP. The resulting code is shorter and easier to read, the
object code is effectively unchanged.
The patch for object.c had to be hand-edited in order to preserve the
comment before the change; Coccinelle tried to eat it for some reason.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The current message printed by "git merge-recursive" for a rename/delete
conflict is like this:
CONFLICT (rename/delete): new-path deleted in HEAD and renamed in
other-branch. Version other-branch of new-path left in tree.
To be more helpful, the message should show both paths of the rename and
state that the deletion occurred at the old path, not the new path. So
change the message to the following format:
CONFLICT (rename/delete): old-path deleted in HEAD and renamed to
new-path in other-branch. Version other-branch of new-path left in tree.
Since this doubles the number of cases in handle_change_delete (modify vs.
rename), refactor the code to halve the number of cases again by merging the
cases where o->branch1 has the change and o->branch2 has the delete with the
cases that are the other way around.
Also add a simple test of the new conflict message.
Signed-off-by: Matt McCutchen <matt@mattmccutchen.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Fix a corner case in merge-recursive regression that crept in
during 2.10 development cycle.
* jc/renormalize-merge-kill-safer-crlf:
convert: git cherry-pick -Xrenormalize did not work
merge-recursive: handle NULL in add_cacheinfo() correctly
cherry-pick: demonstrate a segmentation fault
Git 2.11 had a minor regression in "merge --ff-only" that competed
with another process that simultanously attempted to update the
index. We used to explain what went wrong with an error message,
but the new code silently failed. The error message has been
resurrected.
* jc/lock-report-on-error:
lockfile: LOCK_REPORT_ON_ERROR
hold_locked_index(): align error handling with hold_lockfile_for_update()
wt-status: implement opportunisitc index update correctly
Fix a corner case in merge-recursive regression that crept in
during 2.10 development cycle.
* jc/renormalize-merge-kill-safer-crlf:
convert: git cherry-pick -Xrenormalize did not work
merge-recursive: handle NULL in add_cacheinfo() correctly
cherry-pick: demonstrate a segmentation fault
Callers of the hold_locked_index() function pass 0 when they want to
prepare to write a new version of the index file without wishing to
die or emit an error message when the request fails (e.g. somebody
else already held the lock), and pass 1 when they want the call to
die upon failure.
This option is called LOCK_DIE_ON_ERROR by the underlying lockfile
API, and the hold_locked_index() function translates the paramter to
LOCK_DIE_ON_ERROR when calling the hold_lock_file_for_update().
Replace these hardcoded '1' with LOCK_DIE_ON_ERROR and stop
translating. Callers other than the ones that are replaced with
this change pass '0' to the function; no behaviour change is
intended with this patch.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
Among the callers of hold_locked_index() that passes 0:
- diff.c::refresh_index_quietly() at the end of "git diff" is an
opportunistic update; it leaks the lockfile structure but it is
just before the program exits and nobody should care.
- builtin/describe.c::cmd_describe(),
builtin/commit.c::cmd_status(),
sequencer.c::read_and_refresh_cache() are all opportunistic
updates and they are OK.
- builtin/update-index.c::cmd_update_index() takes a lock upfront
but we may end up not needing to update the index (i.e. the
entries may be fully up-to-date), in which case we do not need to
issue an error upon failure to acquire the lock. We do diagnose
and die if we indeed need to update, so it is OK.
- wt-status.c::require_clean_work_tree() IS BUGGY. It asks
silence, does not check the returned value. Compare with
callsites like cmd_describe() and cmd_status() to notice that it
is wrong to call update_index_if_able() unconditionally.
Merge-recursive sorts a string list using a raw qsort(), where it
feeds the "items" from one struct but the "nr" and size fields from
another struct. This isn't a bug because one list is a copy of the
other, but it's unnecessarily confusing (and also caused our recent
QSORT() cleanups via coccinelle to miss this call site).
Let's use string_list_sort() instead, which is more concise and harder
to get wrong. Note that we need to adjust our comparison function,
which gets fed only the strings now, not the string_list_items. That's
OK because we don't use the "util" field as part of our sort.
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1335d76e45 ("merge: avoid "safer crlf" during recording of merge
results", 2016-07-08) tried to split make_cache_entry() call made
with CE_MATCH_REFRESH into a call to make_cache_entry() without one,
followed by a call to add_cache_entry(), refresh_cache() and another
add_cache_entry() as needed. However the conversion was botched in
that it forgot that refresh_cache() can return NULL, which was
handled correctly in make_cache_entry() but in the updated code.
This fixes https://github.com/git-for-windows/git/issues/952
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When a submodule is being merged or cherry-picked into a working
tree that already contains a corresponding empty directory, do not
record a conflict.
One situation where this bug appears is:
- Commit 1 adds a submodule
- Commit 2 removes that submodule and re-adds it into a subdirectory
(sub1 to sub1/sub1).
- Commit 3 adds an unrelated file.
Now the user checks out commit 1 (first deinitializing the submodule),
and attempts to cherry-pick commit 3. Previously, this would fail,
because the incoming submodule sub1/sub1 would falsely conflict with
the empty sub1 directory.
This patch ignores the empty sub1 directory, fixing the bug. We only
ignore the empty directory if the object being emplaced is a
submodule, which expects an empty directory.
Signed-off-by: David Turner <dturner@twosigma.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Call strbuf_add_unique_abbrev() to add abbreviated hashes to strbufs
instead of taking detours through find_unique_abbrev() and its static
buffer. This is shorter in most cases and a bit more efficient.
The changes here are not easily handled by a semantic patch because
they involve removing temporary variables and deconstructing format
strings for strbuf_addf().
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Code cleanup.
* rs/cocci:
use strbuf_addstr() for adding constant strings to a strbuf, part 2
add coccicheck make target
contrib/coccinelle: fix semantic patch for oid_to_hex_r()
Replace uses of strbuf_addf() for adding strings with more lightweight
strbuf_addstr() calls. This makes the intent clearer and avoids
potential issues with printf format specifiers.
02962d3684 already converted six cases,
this patch covers eleven more.
A semantic patch for Coccinelle is included for easier checking for
new cases that might be introduced in the future.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Since all of its callers have been updated, convert read_mmblob to take
a pointer to struct object_id.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert struct cache_entry to use struct object_id by applying the
following semantic patch and the object_id transforms from contrib, plus
the actual change to the struct:
@@
struct cache_entry E1;
@@
- E1.sha1
+ E1.oid.hash
@@
struct cache_entry *E1;
@@
- E1->sha1
+ E1->oid.hash
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When "git merge-recursive" works on history with many criss-cross
merges in "verbose" mode, the names the command assigns to the
virtual merge bases could have overwritten each other by unintended
reuse of the same piece of memory.
* rs/pull-signed-tag:
commit: use FLEX_ARRAY in struct merge_remote_desc
merge-recursive: fix verbose output for multiple base trees
commit: factor out set_merge_remote_desc()
commit: use xstrdup() in get_merge_parent()
One of the indirect callers of make_virtual_commit() passes the result of
oid_to_hex() as the name, i.e. a pointer to a static buffer. Since the
function uses that string pointer directly in building a struct
merge_remote_desc, multiple entries can end up sharing the same name
inadvertently.
Fix that by calling set_merge_remote_desc(), which creates a copy of the
string, instead of building the struct by hand.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Initialize a string_list right when it's defined. That's shorter, saves
a function call and makes it more obvious that we're using the NODUP
variant here.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Ever since 66a155b (Enable output buffering in merge-recursive.,
2007-01-14), we had a problem: When the merge failed in a fatal way, all
regular output was swallowed because we called die() and did not get a
chance to drain the output buffers.
To fix this, several modifications were necessary:
- we needed to stop die()ing, to give callers a chance to do something
when an error occurred (in this case, flush the output buffers),
- we needed to delay printing the error message so that the caller can
print the buffered output before that, and
- we needed to make sure that the output buffers are flushed even when
the return value indicates an error.
The first two changes were introduced through earlier commits in this
patch series, and this commit addresses the third one.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The recursive merge machinery accumulates its output in an output
buffer, to be flushed at the end of merge_recursive(). At this point,
we forgot to release the output buffer.
When calling merge_trees() (i.e. the non-recursive part of the recursive
merge) directly, the output buffer is never flushed because the caller
may be merge_recursive() which wants to flush the output itself.
For the same reason, merge_trees() cannot release the output buffer: it
may still be needed.
Forgetting to release the output buffer did not matter much when running
git-checkout, or git-merge-recursive, because we exited after the
operation anyway. Ever since cherry-pick learned to pick a commit range,
however, this memory leak had the potential of becoming a problem.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Since 66a155b (Enable output buffering in merge-recursive., 2007-01-14),
we already accumulate the output in a buffer. The idea was to avoid
interfering with the progress output that goes to stderr, which is
unbuffered, when we write to stdout, which is buffered.
We extend that buffering to allow the caller to handle the output
(possibly suppressing it). This will help us when extending the
sequencer to do rebase -i's brunt work: it does not want the picks to
print anything by default but instead determine itself whether to print
the output or not.
Note that we also redirect the error messages into the output buffer
when the caller asked not to flush the output buffer, for two reasons:
1) to retain the correct output order, and 2) to allow the caller to
suppress *all* output.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In 66a155b (Enable output buffering in merge-recursive., 2007-01-14), we
changed the code such that it prints the output in one go, to avoid
interfering with the progress output.
Let's make sure that the same holds true when outputting the commit
title: previously, we used several printf() statements to stdout and
assumed that stdout's buffer is large enough to hold the entire
commit title.
Apart from making that speculation unnecessary, we change the code to
add the message to the output buffer before flushing for another reason:
the next commit will introduce a new level of output buffering, where
the caller can request the output not to be flushed, but to be retained
for further processing.
This latter feature will be needed when teaching the sequencer to do
rebase -i's brunt work: it wants to control the output of the
cherry-picks (i.e. recursive merges).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The data structure passed to the recursive merge machinery has a feature
where the caller can ask for the output to be buffered into a strbuf, by
setting the field 'buffer_output'.
Previously, we died without flushing, losing accumulated output. With
this patch, we show the output first, and only then print the error
message.
Currently, the only user of that buffering is merge_recursive() itself,
to avoid the progress output to interfere.
In the next patches, we will introduce a new buffer_output mode that
forces merge_recursive() to retain the output buffer for further
processing by the caller. If the caller asked for that, we will then
also write the error messages into the output buffer. This is necessary
to give the caller more control not only how to react in case of errors
but also control how/if to display the error messages.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The recursive merge machinery is supposed to be a library function, i.e.
it should return an error when it fails. Originally the functions were
part of the builtin "merge-recursive", though, where it was simpler to
call die() and be done with error handling.
The existing callers were already prepared to detect negative return
values to indicate errors and to behave as previously: exit with code 128
(which is the same thing that die() does, after printing the message).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We are about to libify the recursive merge machinery, where we only
die() in case of a bug or memory contention. To that end, we must heed
negative return values as indicating errors.
This requires our functions to be careful to pass through error
conditions in call chains, and for quite a few functions this means
that they have to return values to begin with.
The next step will be to convert the places where we currently die() to
return negative values (read: -1) instead.
Note that we ignore errors reported by make_room_for_path(), consistent
with the previous behavior (update_file_flags() used the return value of
make_room_for_path() only to indicate an early return, but not a fatal
error): if the error is really a fatal error, we will notice later; If
not, it was not that serious a problem to begin with. (Witnesses in
favor of this reasoning are t4151-am-abort and t7610-mergetool, which
would start failing if we stopped on errors reported by
make_room_for_path()).
Also note: while this patch makes the code slightly less readable in
update_file_flags() (we introduce a new "goto free_buf;" instead of
an explicit "free(buf); return;"), it is a preparatory change for
the next patch where we will convert all of the die() calls in the same
function to go through the free_buf return path instead.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
It is possible that a tree cannot be written (think: disk full). We
will want to give the caller a chance to clean up instead of letting
the program die() in such a case.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
It is technically allowed, as per C89, for functions' return type to
be complete structs (i.e. *not* just pointers to structs).
However, it was just an oversight of this developer when converting
Python code to C code in 6d297f8 (Status update on merge-recursive in
C, 2006-07-08) which introduced such a return type.
Besides, by converting this construct to pass in the struct, we can now
start returning a value that can indicate errors in future patches. This
will help the current effort to libify merge-recursive.c.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There are a couple of places where return values never indicated errors
before, as we simply died instead of returning.
But now negative return values mean that there was an error and we have to
abort the operation. Let's do exactly that.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
It can be puzzling to see that was_tracked() asks to get an index entry
by name, but does not take a negative return value for an answer.
The reason we have to do this is that cache_name_pos() only looks for
entries in stage 0, even if nobody asked for any stage in particular.
Let's rewrite the logic a little bit, to handle the easy case early: if
cache_name_pos() returned a non-negative position, we know it is a match,
and we do not even have to compare the name again (cache_name_pos() did
that for us already). We can say right away: yes, this file was tracked.
Only if there was no exact match do we need to look harder for any
matching entry in stage 2.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
While working on the patch series that avoids die()ing in recursive
merges, the issue came up that bug reports (i.e. die("BUG: ...")
constructs) should never be translated, as the target audience is the
Git developer community, not necessarily the current user, and hence
a translated message would make it *harder* to address the problem.
So let's stop translating the obvious ones. As it is really, really
outside the purview of this patch series to see whether there are more
die() statements that report bugs and are currently translated, that
task is left for another day and patch.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The vast majority of error messages in Git's source code which report a
bug use the convention to prefix the message with "BUG:".
As part of cleaning up merge-recursive to stop die()ing except in case of
detected bugs, let's just make the remainder of the bug reports consistent
with the de facto rule.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
"git merge" with renormalization did not work well with
merge-recursive, due to "safer crlf" conversion kicking in when it
shouldn't.
* jc/renormalize-merge-kill-safer-crlf:
merge: avoid "safer crlf" during recording of merge results
convert: unify the "auto" handling of CRLF
When merge_recursive() decides what the correct blob object merge
result for a path should be, it uses update_file_flags() helper
function to write it out to a working tree file and then calls
add_cacheinfo(). The add_cacheinfo() function in turn calls
make_cache_entry() to create a new cache entry to replace the
higher-stage entries for the path that represents the conflict.
The make_cache_entry() function calls refresh_cache_entry() to fill
in the cached stat information. To mark a cache entry as
up-to-date, the data is re-read from the file in the working tree,
and goes through convert_to_git() conversion to be compared with the
blob object name the new cache entry records.
It is important to note that this happens while the higher-stage
entries, which are going to be replaced with the new entry, are
still in the index. Unfortunately, the convert_to_git() conversion
has a misguided "safer crlf" mechanism baked in, and looks at the
existing cache entry for the path to decide how to convert the
contents in the working tree file. If our side (i.e. stage#2)
records a text blob with CRLF in it, even when the system is
configured to record LF in blobs and convert them to CRLF upon
checkout (and back to LF upon checkin), the "safer crlf" mechanism
stops us doing so.
This especially poses a problem during a renormalizing merge, where
the merge result for the path is computed by first "normalizing" the
blobs involved in the merge by using convert_to_working_tree()
followed by convert_to_git() with "safer crlf" disabled. The merge
result that is computed correctly and fed to add_cacheinfo() via
update_file_flags() does _not_ match what refresh_cache_entry() sees
by converting the working tree file via convert_to_git().
We can work this around by not refreshing the new cache entry in
make_cache_entry() called by add_cacheinfo(). After add_cacheinfo()
adds the new entry, we can call refresh_cache_entry() on that,
knowing that addition of this new cache entry would have removed the
stale cache entries that had CRLF in stage #2 that were carried over
before the renormalizing merge started and will not interfere with
the correct recording of the result.
The test update was taken from a series by Torsten Bögershausen
that attempted to fix this with a different approach.
Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Reviewed-by: Torsten Bögershausen <tboegi@web.de>
Convert this function and the git merge-recursive subcommand to use
struct object_id.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert all but two of the static functions in this file to use struct
object_id.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert struct merge_file_info to use struct object_id. The following
Coccinelle semantic patch was used to implement this, followed by the
transformations in object_id.cocci:
@@
struct merge_file_info o;
@@
- o.sha
+ o.oid.hash
@@
struct merge_file_info *p;
@@
- p->sha
+ p->oid.hash
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert the anonymous struct within struct stage_data to use struct
object_id. The following Coccinelle semantic patch was used to
implement this, followed by the transformations in object_id.cocci:
@@
struct stage_data o;
expression E1;
@@
- o.stages[E1].sha
+ o.stages[E1].oid.hash
@@
struct stage_data *p;
expression E1;
@@
- p->stages[E1].sha
+ p->stages[E1].oid.hash
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert struct diff_filespec's sha1 member to use a struct object_id
called "oid" instead. The following Coccinelle semantic patch was used
to implement this, followed by the transformations in object_id.cocci:
@@
struct diff_filespec o;
@@
- o.sha1
+ o.oid.hash
@@
struct diff_filespec *p;
@@
- p->sha1
+ p->oid.hash
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move from unsigned char[20] to struct object_id continues.
* bc/object-id:
match-trees: convert several leaf functions to use struct object_id
tree-walk: convert tree_entry_extract() to use struct object_id
struct name_entry: use struct object_id instead of unsigned char sha1[20]
match-trees: convert shift_tree() and shift_tree_by() to use object_id
test-match-trees: convert to use struct object_id
sha1-name: introduce a get_oid() function
There were a few cases in merge-recursive that could result in a
check for the presence of files in the working copy while trying to
create a virtual merge base. These were rare and innocuous, but
somewhat illogical. The two cases were:
* When there was naming conflicts (e.g. a D/F conflict) and we had to
pick a new unique name for a file. Since the new name is somewhat
arbitrary, it didn't matter that we consulted the working copy to
avoid picking a filename it has, but since the virtual merge base is
never checked out, it's a waste of time and slightly odd to do so.
* When two different files get renamed to the same name (on opposite
sides of the merge), we needed to delete the original filenames from
the cache and possibly also the working directory. The caller's check
for determining whether to delete from the working directory was a
call to would_lose_untracked(). It turns out this didn't matter
because remove_file() had logic to avoid modifying the working
directory when creating a virtual merge base, but there is no reason
for the caller to check the working directory in such circumstances.
It's a waste of time, if not also a bit weird.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In commit 51931bf (merge-recursive: Improve handling of rename
target vs. directory addition, 2011-08-11), I apparently added two
lines of code that were immediately duplicated a few lines later.
No idea why, other than it seems pretty clear this was a mistake:
there is no need to remove the same file twice; removing it once is
sufficient...especially since the intervening line was working with
a different file entirely.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Make the find-renames option follow the behaviour in git-diff, where it
resets the threshold when none is given. So, for instance,
"--find-renames=25 --find-renames" should result in the default
threshold (50%) instead of 25%.
Signed-off-by: Felipe Gonçalves Assis <felipegassis@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add strategy option find-renames, following git-diff interface. This
makes the option rename-threshold redundant.
Signed-off-by: Felipe Gonçalves Assis <felipegassis@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The recursive strategy turns on rename detection by default. Add a
strategy option to disable rename detection even for exact renames.
Signed-off-by: Felipe Gonçalves Assis <felipegassis@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert all instances of get_object_hash to use an appropriate reference
to the hash member of the oid member of struct object. This provides no
functional change, as it is essentially a macro substitution.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Jeff King <peff@peff.net>
Junio C Hamano
René Scharfe
Matt McCutchen
Nguyễn Thái Ngọc Duy
Johannes Schindelin
David Turner
brian m. carlson
Elijah Newren
Felipe Gonçalves Assis