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Git Forges may be interested in whether two branches can be merged while
not being interested in what the resulting merge tree is nor which files
conflicted. For such cases, add a new mergeability_only option. This
option allows the merge machinery to, in the "outer layer" of the merge:
* exit upon first[-ish] conflict
* avoid (not prevent) writing merged blobs/trees to the object store
I have a number of qualifiers there, so let me explain each:
"outer layer":
Note that since the recursive merge of merge bases (corresponding to
call_depth > 0) can conflict without the outer final merge
(corresponding to call_depth == 0) conflicting, we can't short-circuit
nor avoid writing merged blobs/trees to the object store during those
inner merges.
"first-ish conflict":
The current patch only exits early from process_entries() on the first
conflict it detects, but conflicts could have been detected in a
previous function call, namely detect_and_process_renames(). However:
* conflicts detected by detect_and_process_renames() are quite rare
conflict types
* the detection would still come after regular rename detection
(which is the expensive part of detect_and_process_renames()), so
it is not saving us much in computation time given that
process_entries() directly follows detect_and_process_renames()
* [this overlaps with the next bullet point] process_entries() is the
place where virtually all object writing occurs (object writing is
sometimes more of a concern for Forges than computation time), so
exiting early here isn't saving us much in object writes either
* the code changes needed to handle an earlier exit are slightly
more invasive in detect_and_process_renames() than for
process_entries().
Given the rareness of the even earlier conflicts, the limited savings
we'd get from exiting even earlier, and in an attempt to keep this
patch simpler, we don't guarantee that we actually exit on the first
conflict detected. We can always revisit this decision later if we
decide that a further micro-optimization to exit slightly earlier in
rare cases is worthwhile.
"avoid (not prevent) writing objects":
The detect_and_process_renames() call can also write objects to the
object store, when rename/rename conflicts involve one (or more) files
that have also been modified on both sides. Because of this alternate
call path leading to handle_content_merges(), our "early exit" does not
prevent writing objects entirely, even within the "outer layer"
(i.e. even within call_depth == 0). I figure that's fine though, since
we're already writing objects for the inner merges (i.e. for call_depth
> 0), which are likely going to represent vastly more objects than files
involved in rename/rename+modify/modify cases in the outer merge, on
average.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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As a wise man once told me, "Deleted code is debugged code!" So, move
the functions that are shared between merge-recursive and merge-ort from
the former to the latter, and then debug the remainder of
merge-recursive.[ch].
Joking aside, merge-ort was always intended to replace merge-recursive.
It has numerous advantages over merge-recursive (operates much faster,
can operate without a worktree or index, and fixes a number of known
bugs and suboptimal merges). Since we have now replaced all callers of
merge-recursive with equivalent functions from merge-ort, move the
shared functions from the former to the latter, and delete the remainder
of merge-recursive.[ch].
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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merge-recursive.[ch] have three entry points:
* merge_trees()
* merge_recursive()
* merge_recursive_generic()
merge-ort*.[ch] only has equivalents for the first two. Add an
equivalent for the final entry point, so we can switch callers to
use it and remove merge-recursive.[ch].
While porting it over, finally fix the issue with the label for the
ancestor (used when merge.conflictStyle=diff3 as a conflict label).
merge-recursive.c has traditionally not allowed callers to set that
label, but I have found that problematic for years.
(Side note: This function was initially part of the merge-ort rewrite,
but reviewers questioned the ancestor label funnyness which I was
never really happy with anyway. It resulted in me jettisoning it and
hoping at the time that I would eventually be able to force the existing
callers to use some other API. That worked with `git stash`, as per
874cf2a60444 (stash: apply stash using 'merge_ort_nonrecursive()',
2022-05-10), but this API is the most reasonable one for `git am` and
`git merge-recursive`, if we can just allow them some freedom over the
ancestor label.)
The merge_recursive_generic() function did not know whether it was being
invoked by `git stash`, `git merge-recursive`, or `git am`, and the
choice of meaningful ancestor label, when there is a unique ancestor,
varies for these different callers:
* git am: ancestor is a constructed "fake ancestor" that user knows
nothing about and has no access to. (And is different than
the normal thing we mean by a "virtual merge base" which is
the merging of merge bases.)
* git merge-recursive: ancestor might be a tree, but at least it
was one specified by the user (if they invoked
merge-recursive directly)
* git stash: ancestor was the commit serving as the stash base
Thus, using a label like "constructed merge base" (as
merge_recursive_generic() does) presupposes that `git am` is the only
caller; it is incorrect for other callers. This label has thrown me off
more than once. Allow the caller to override when there is a unique
merge base.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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More memory leaks have been plugged.
* ps/leakfixes-more: (29 commits)
builtin/blame: fix leaking ignore revs files
builtin/blame: fix leaking prefixed paths
blame: fix leaking data for blame scoreboards
line-range: plug leaking find functions
merge: fix leaking merge bases
builtin/merge: fix leaking `struct cmdnames` in `get_strategy()`
sequencer: fix memory leaks in `make_script_with_merges()`
builtin/clone: plug leaking HEAD ref in `wanted_peer_refs()`
apply: fix leaking string in `match_fragment()`
sequencer: fix leaking string buffer in `commit_staged_changes()`
commit: fix leaking parents when calling `commit_tree_extended()`
config: fix leaking "core.notesref" variable
rerere: fix various trivial leaks
builtin/stash: fix leak in `show_stash()`
revision: free diff options
builtin/log: fix leaking commit list in git-cherry(1)
merge-recursive: fix memory leak when finalizing merge
builtin/merge-recursive: fix leaking object ID bases
builtin/difftool: plug memory leaks in `run_dir_diff()`
object-name: free leaking object contexts
...
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The "hash-ll.h" header was introduced via d1cbe1e6d8 (hash-ll.h: split
out of hash.h to remove dependency on repository.h, 2023-04-22) to make
explicit the split between hash-related functions that rely on the
global `the_repository`, and those that don't. This split is no longer
necessary now that we we have removed the reliance on `the_repository`.
Merge "hash-ll.h" back into "hash.h". This causes some code units to not
include "repository.h" anymore, which requires us to add some forward
declarations.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When calling either the recursive or the ORT merge machineries we need
to provide a list of merge bases. The ownership of that parameter is
then implicitly transferred to the callee, which is somewhat fishy.
Furthermore, that list may leak in some cases where the merge machinery
runs into an error, thus causing a memory leak.
Refactor the code such that we stop transferring ownership. Instead, the
merge machinery will now create its own local copies of the passed in
list as required if they need to modify the list. Free the list at the
callsites as required.
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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hash.h depends upon and includes repository.h, due to the definition and
use of the_hash_algo (defined as the_repository->hash_algo). However,
most headers trying to include hash.h are only interested in the layout
of the structs like object_id. Move the parts of hash.h that do not
depend upon repository.h into a new file hash-ll.h (the "low level"
parts of hash.h), and adjust other files to use this new header where
the convenience inline functions aren't needed.
This allows hash.h and object.h to be fairly small, minimal headers. It
also exposes a lot of hidden dependencies on both path.h (which was
brought in by repository.h) and repository.h (which was previously
implicitly brought in by object.h), so also adjust other files to be
more explicit about what they depend upon.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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With the new `detailed` parameter, a new mode can be triggered when
displaying the merge messages: The `detailed` mode prints NUL-delimited
fields of the following form:
<path-count> NUL <path>... NUL <conflict-type> NUL <message>
The `<path-count>` field determines how many `<path>` fields there are.
The intention of this mode is to support server-side operations, where
worktree-less merges can lead to conflicts and depending on the type
and/or path count, the caller might know how to handle said conflict.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This allows us once again to get away with less data copying.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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To prepare for using the `merge-ort` machinery in server operations, we
cannot simply produce a free-form string that combines a variable-length
list of messages.
Instead, we need to list them one by one. The natural fit for this is a
`string_list`.
We will subsequently add even more information in the `util` attribute
of the string list items.
Based-on-a-patch-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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After a merge, this function allows the user to extract the same
information that would be printed by `ls-files -u`, which means
files with their mode, oid, and stage.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This patch includes no new code; it simply moves a bunch of lines into a
new function. As such, there are no functional changes. This is just a
preparatory step to allow the printed messages to be handled differently
by other callers, such as in `git merge-tree --write-tree`.
(Patch best viewed with
--color-moved --color-moved-ws=allow-indentation-change
to see that it is a simple code movement.)
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Conflicts such as modify/delete, rename/rename, or file/directory are
not representable via content conflict markers, and the normal output
messages notifying users about these were dropped with --remerge-diff.
While we don't want these messages randomly shown before the commit
and diff headers, we do want them to still be shown; include them as
part of the diff headers instead.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Previously, callers of the merge-ort API could have passed an
uninitialized value for struct merge_result *result. However, we want
to check result to see if it has cached renames from a previous merge
that we can reuse; such values would be found behind result->priv.
However, if result->priv is uninitialized, attempting to access behind
it will give a segfault. So, we need result->priv to be NULL (which
will be the case if the caller does a memset(&result, 0)), or be written
by a previous call to the merge-ort machinery. Documenting this
requirement may help, but despite being the person who introduced this
requirement, I still missed it once and it did not fail in a very clear
way and led to a long debugging session.
Add a _properly_initialized field to merge_result; that value will be
0 if the caller zero'ed the merge_result, it will be set to a very
specific value by a previous run by the merge-ort machinery, and if it's
uninitialized it will most likely either be 0 or some value that does
not match the specific one we'd expect allowing us to throw a much more
meaningful error.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Implement merge_incore_recursive(), mostly through the use of a new
helper function, merge_ort_internal(), which itself is based off
merge_recursive_internal() from merge-recursive.c.
This drops the number of failures in the testsuite when run under
GIT_TEST_MERGE_ALGORITHM=ort from around 1500 to 647.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Various places in merge-recursive used an err() function when it hit
some kind of unrecoverable error. That code was from the reusable bits
of merge-recursive.c that we liked, such as merge_3way, writing object
files to the object store, reading blobs from the object store, etc. So
create a similar function to allow us to port that code over, and use it
for when we detect problems returned from collect_merge_info()'s
traverse_trees() call, which we will be adding next.
While we are at it, also add more documentation for the "clean" field
from struct merge_result, particularly since the name suggests a boolean
but it is not quite one and this is our first non-boolean usage.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This is the beginning of a new merge strategy. While there are some API
differences, and the implementation has some differences in behavior, it
is essentially meant as an eventual drop-in replacement for
merge-recursive.c. However, it is being built to exist side-by-side
with merge-recursive so that we have plenty of time to find out how
those differences pan out in the real world while people can still fall
back to merge-recursive. (Also, I intend to avoid modifying
merge-recursive during this process, to keep it stable.)
The primary difference noticable here is that the updating of the
working tree and index is not done simultaneously with the merge
algorithm, but is a separate post-processing step. The new API is
designed so that one can do repeated merges (e.g. during a rebase or
cherry-pick) and only update the index and working tree one time at the
end instead of updating it with every intermediate result. Also, one
can perform a merge between two branches, neither of which match the
index or the working tree, without clobbering the index or working tree.
The next three commits will demonstrate various uses of this new API.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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