Code cleanup around struct_type_init() functions.
* ab/struct-init:
string-list.h users: change to use *_{nodup,dup}()
string-list.[ch]: add a string_list_init_{nodup,dup}()
dir.[ch]: replace dir_init() with DIR_INIT
*.c *_init(): define in terms of corresponding *_INIT macro
*.h: move some *_INIT to designated initializers
The merge code had funny interactions between content based rename
detection and directory rename detection.
* en/merge-dir-rename-corner-case-fix:
merge-recursive: handle rename-to-self case
merge-ort: ensure we consult df_conflict and path_conflicts
t6423: test directory renames causing rename-to-self
Performance tweaks of "git merge -sort" around lazy fetching of objects.
* en/ort-perf-batch-13:
merge-ort: add prefetching for content merges
diffcore-rename: use a different prefetch for basename comparisons
diffcore-rename: allow different missing_object_cb functions
t6421: add tests checking for excessive object downloads during merge
promisor-remote: output trace2 statistics for number of objects fetched
More fix-ups and optimization to "merge -sort".
* en/ort-perf-batch-12:
merge-ort: miscellaneous touch-ups
Fix various issues found in comments
diffcore-rename: avoid unnecessary strdup'ing in break_idx
merge-ort: replace string_list_df_name_compare with faster alternative
Change all in-tree users of the string_list_init(LIST, BOOL) API to
use string_list_init_{nodup,dup}(LIST) instead.
As noted in the preceding commit let's leave the now-unused
string_list_init() wrapper in-place for any in-flight users, it can be
removed at some later date.
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Path conflicts (typically rename path conflicts, e.g.
rename/rename(1to2) or rename/add/delete), and directory/file conflicts
should obviously result in files not being marked as clean in the merge.
We had a codepath where we missed consulting the path_conflict and
df_conflict flags, based on match_mask. Granted, it requires an unusual
setup to trigger this codepath (directory rename causing rename-to-self
is the only case I can think of), but we still need to handle it. To
make it clear that we have audited the other codepaths that do not
explicitly mention these flags, add some assertions that the flags are
not set.
Reported-by: Anders Kaseorg <andersk@mit.edu>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Commit 7fbbcb21b1 ("diff: batch fetching of missing blobs", 2019-04-05)
introduced batching of fetching missing blobs, so that the diff
machinery would have one fetch subprocess grab N blobs instead of N
processes each grabbing 1.
However, the diff machinery is not the only thing in a merge that needs
to work on blobs. The 3-way content merges need them as well. Rather
than download all the blobs 1 at a time, prefetch all the blobs needed
for regular content merges.
This does not cover all possible paths in merge-ort that might need to
download blobs. Others include:
- The blob_unchanged() calls to avoid modify/delete conflicts (when
blob renormalization results in an "unchanged" file)
- Preliminary content merges needed for rename/add and
rename/rename(2to1) style conflicts. (Both of these types of
conflicts can result in nested conflict markers from the need to do
two levels of content merging; the first happens before our new
prefetch_for_content_merges() function.)
The first of these wouldn't be an extreme amount of work to support, and
even the second could be theoretically supported in batching, but all of
these cases seem unusual to me, and this is a minor performance
optimization anyway; in the worst case we only get some of the fetches
batched and have a few additional one-off fetches. So for now, just
handle the regular 3-way content merges in our prefetching.
For the testcase from the previous commit, the number of downloaded
objects remains at 63, but this drops the number of fetches needed from
32 down to 20, a sizeable reduction.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Optimize out repeated rename detection in a sequence of mergy
operations.
* en/ort-perf-batch-11:
merge-ort, diffcore-rename: employ cached renames when possible
merge-ort: handle interactions of caching and rename/rename(1to1) cases
merge-ort: add helper functions for using cached renames
merge-ort: preserve cached renames for the appropriate side
merge-ort: avoid accidental API mis-use
merge-ort: add code to check for whether cached renames can be reused
merge-ort: populate caches of rename detection results
merge-ort: add data structures for in-memory caching of rename detection
t6429: testcases for remembering renames
fast-rebase: write conflict state to working tree, index, and HEAD
fast-rebase: change assert() to BUG()
Documentation/technical: describe remembering renames optimization
t6423: rename file within directory that other side renamed
Add some notes in the code about invariants with match_mask when adding
pairs. Also add a comment that seems to have been left out in my work
of pushing these changes upstream.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A random hodge-podge of incorrect or out-of-date comments that I found:
* t6423 had a comment that has referred to the wrong test for years;
fix it to refer to the right one.
* diffcore-rename had a FIXME comment meant to remind myself to
investigate if I could make another code change. I later
investigated and removed the FIXME, but while cherry-picking the
patch to submit upstream I missed the later update. Remove the
comment now.
* merge-ort had the early part of a comment for a function; I had
meant to include the more involved description when I updated the
function. Update the comment now.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Gathering accumulated times from trace2 output on the mega-renames
testcase, I saw the following timings (where I'm only showing a few
lines to highlight the portions of interest):
10.120 : label:incore_nonrecursive
4.462 : ..label:process_entries
3.143 : ....label:process_entries setup
2.988 : ......label:plist special sort
1.305 : ....label:processing
2.604 : ..label:collect_merge_info
2.018 : ..label:merge_start
1.018 : ..label:renames
In the above output, note that the 4.462 seconds for process_entries was
split as 3.143 seconds for "process_entries setup" and 1.305 seconds for
"processing" (and a little time for other stuff removed from the
highlight). Most of the "process_entries setup" time was spent on
"plist special sort" which corresponds to the following code:
trace2_region_enter("merge", "plist special sort", opt->repo);
plist.cmp = string_list_df_name_compare;
string_list_sort(&plist);
trace2_region_leave("merge", "plist special sort", opt->repo);
In other words, in a merge strategy that would be invoked by passing
"-sort" to either rebase or merge, sorting an array takes more time than
anything else. Serves me right for naming my merge strategy this way.
Rewrite the comparison function in a way that does not require finding
out the lengths of the strings when comparing them. While at it, tweak
the code for our specific case -- no need to handle a variety of modes,
for example. The combination of these changes reduced the time spent in
"plist special sort" by ~25% in the mega-renames case.
For the testcases mentioned in commit 557ac0350d ("merge-ort: begin
performance work; instrument with trace2_region_* calls", 2020-10-28),
this change improves the performance as follows:
Before After
no-renames: 5.622 s ± 0.059 s 5.235 s ± 0.042 s
mega-renames: 10.127 s ± 0.073 s 9.419 s ± 0.107 s
just-one-mega: 500.3 ms ± 3.8 ms 480.1 ms ± 3.9 ms
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When there are many renames between the old base of a series of commits
and the new base, the way sequencer.c, merge-recursive.c, and
diffcore-rename.c have traditionally split the work resulted in
redetecting the same renames with each and every commit being
transplanted. To address this, the last several commits have been
creating a cache of rename detection results, determining when it was
safe to use such a cache in subsequent merge operations, adding helper
functions, and so on. See the previous half dozen commit messages for
additional discussion of this optimization, particularly the message a
few commits ago entitled "add code to check for whether cached renames
can be reused". This commit finally ties all of that work together,
modifying the merge algorithm to make use of these cached renames.
For the testcases mentioned in commit 557ac0350d ("merge-ort: begin
performance work; instrument with trace2_region_* calls", 2020-10-28),
this change improves the performance as follows:
Before After
no-renames: 5.665 s ± 0.129 s 5.622 s ± 0.059 s
mega-renames: 11.435 s ± 0.158 s 10.127 s ± 0.073 s
just-one-mega: 494.2 ms ± 6.1 ms 500.3 ms ± 3.8 ms
That's a fairly small improvement, but mostly because the previous
optimizations were so effective for these particular testcases; this
optimization only kicks in when the others don't. If we undid the
basename-guided rename detection and skip-irrelevant-renames
optimizations, then we'd see that this series by itself improved
performance as follows:
Before Basename Series After Just This Series
no-renames: 13.815 s ± 0.062 s 5.697 s ± 0.080 s
mega-renames: 1799.937 s ± 0.493 s 205.709 s ± 0.457 s
Since this optimization kicks in to help accelerate cases where the
previous optimizations do not apply, this last comparison shows that
this cached-renames optimization has the potential to help signficantly
in cases that don't meet the requirements for the other optimizations to
be effective.
The changes made in this optimization also lay some important groundwork
for a future optimization around having collect_merge_info() avoid
recursing into subtrees in more cases.
However, for this optimization to be effective, merge_switch_to_result()
should only be called when the rebase or cherry-pick operation has
either completed or hit a case where the user needs to resolve a
conflict or edit the result. If it is called after every commit, as
sequencer.c does, then the working tree and index are needlessly updated
with every commit and the cached metadata is tossed, defeating this
optimization. Refactoring sequencer.c to only call
merge_switch_to_result() at the end of the operation is a bigger
undertaking, and the practical benefits of this optimization will not be
realized until that work is performed. Since `test-tool fast-rebase`
only updates at the end of the operation, it was used to obtain the
timings above.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
As documented in Documentation/technical/remembering-renames.txt, and as
tested for in the two testcases in t6429 with "rename same file
identically" in their description, there is one case where we need to
have renames in one commit NOT be cached for the next commit in our
rebase sequence -- namely, rename/rename(1to1) cases. Rather than
specifically trying to uncache those and fix up dir_rename_counts() to
match (which would also be valid but more work), we simply disable the
optimization when this really rare type of rename occurs.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If we have a usable rename cache, then we can remove from
relevant_sources all the paths that were cached;
diffcore_rename_extended() can then consider an even smaller set of
relevant_sources in its rename detection.
However, when diffcore_rename_extended() is done, we will need to take
the renames it detected and then add back in all the ones we had cached
from before.
Add helper functions for doing these two operations; the next commit
will make use of them.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Previous commits created an in-memory cache of the results of rename
detection, and added logic to detect when that cache could appropriately
be used in a subsequent merge operation -- but we were still
unconditionally clearing the cache with each new merge operation anyway.
If it is valid to reuse the cache from one of the two sides of history,
preserve that side.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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>
We need to know when renames detected in a previous merge operation can
be reused in a later merge operation. Consider the following setup
(from the git-rebase manpage):
A---B---C topic
/
D---E---F---G master
After rebasing, this will appear as:
A'--B'--C' topic
/
D---E---F---G master
Further, let's say that 'oldfile' was renamed to 'newfile' between E
and G. The rebase or cherry-pick of A onto G will involve a three-way
merge between E (as the merge base) and G and A. After detecting the
rename between E:oldfile and G:newfile, there will be a three-way
content merge of the following:
E:oldfile
G:newfile
A:oldfile
and produce a new result:
A':newfile
Now, when we want to pick B onto A', we will need to do a three-way
merge between A (as the merge-base) and A' and B. This will involve
a three-way content merge of
A:oldfile
A':newfile
B:oldfile
but only if we can detect that A:oldfile is similar enough to A':newfile
to be used together in a three-way content merge, i.e. only if we can
detect that A:oldfile and A':newfile are a rename. But we already know
that A:oldfile and A':newfile are similar enough to be used in a
three-way content merge, because that is precisely where A':newfile came
from in the previous merge.
Note that A & A' both appear in both merges. That gives us the
condition under which we can reuse renames.
There are a couple important points about this optimization:
- If the rebase or cherry-pick halts for user conflicts, these caches
are NOT saved anywhere. Thus, resuming a halted rebase or
cherry-pick will result in no reused renames for the next commit.
This is intentional, as user resolution can change files
significantly and in ways that violate the similarity assumptions
here.
- Technically, in a *very* narrow case this might give slightly
different results for rename detection. Using the example above,
if:
* E:oldfile had 20 lines
* G:newfile added 10 new lines at the beginning of the file
* A:oldfile deleted all but the first three lines of the file
then
=> A':newfile would have 13 lines, 3 of which matches those
in A:oldfile.
Consider the two cases:
* Without this optimization:
- the next step of the rebase operation (moving B to B')
would not detect the rename betwen A:oldfile and A':newfile
- we'd thus get a modify/delete conflict with the rebase
operation halting for the user to resolve, and have both
A':newfile and B:oldfile sitting in the working tree.
* With this optimization:
- the rename between A:oldfile and A':newfile would be detected
via the cache of renames
- a three-way merge between A:oldfile, A':newfile, and B:oldfile
would commence and be written to A':newfile
Now, is the difference in behavior a bug...or a bugfix? I can't
tell. Given that A:oldfile and A':newfile are not very similar,
when we three-way merge with B:oldfile it seems likely we'll hit a
conflict for the user to resolve. And it shouldn't be too hard for
users to see why we did that three-way merge; oldfile and newfile
*were* renames somewhere in the sequence. So, most of these corner
cases will still behave similarly -- namely, a conflict given to the
user to resolve. Also, consider the interesting case when commit B
is a clean revert of commit A. Without this optimization, a rebase
could not both apply a weird patch like A and then immediately
revert it; users would be forced to resolve merge conflicts. With
this optimization, it would successfully apply the clean revert.
So, there is certainly at least one case that behaves better. Even
if it's considered a "difference in behavior", I think both behaviors
are reasonable, and the time savings provided by this optimization
justify using the slightly altered rename heuristics.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Fill in cache_pairs, cached_target_names, and cached_irrelevant based on
rename detection results. Future commits will make use of these values.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When there are many renames between the old base of a series of commits
and the new base for a series of commits, the sequence of merges
employed to transplant those commits (from a cherry-pick or rebase
operation) will repeatedly detect the exact same renames. This is
wasted effort.
Add data structures which will be used to cache rename detection
results, along with the initialization and deallocation of these data
structures. Future commits will populate these caches, detect the
appropriate circumstances when they can be used, and employ them to
avoid re-detecting the same renames repeatedly.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The word "renamed" has two possible translations in many European
languages depending on whether one thing was renamed or two things were
renamed. Give translators freedom to alter any part of the message to
make it sound right in their language.
Signed-off-by: Alex Henrie <alexhenrie24@gmail.com>
Acked-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
SHA-256 transition.
* bc/hash-transition-interop-part-1:
hex: print objects using the hash algorithm member
hex: default to the_hash_algo on zero algorithm value
builtin/pack-objects: avoid using struct object_id for pack hash
commit-graph: don't store file hashes as struct object_id
builtin/show-index: set the algorithm for object IDs
hash: provide per-algorithm null OIDs
hash: set, copy, and use algo field in struct object_id
builtin/pack-redundant: avoid casting buffers to struct object_id
Use the final_oid_fn to finalize hashing of object IDs
hash: add a function to finalize object IDs
http-push: set algorithm when reading object ID
Always use oidread to read into struct object_id
hash: add an algo member to struct object_id
Builds on top of the sparse-index infrastructure to mark operations
that are not ready to mark with the sparse index, causing them to
fall back on fully-populated index that they always have worked with.
* ds/sparse-index-protections: (47 commits)
name-hash: use expand_to_path()
sparse-index: expand_to_path()
name-hash: don't add directories to name_hash
revision: ensure full index
resolve-undo: ensure full index
read-cache: ensure full index
pathspec: ensure full index
merge-recursive: ensure full index
entry: ensure full index
dir: ensure full index
update-index: ensure full index
stash: ensure full index
rm: ensure full index
merge-index: ensure full index
ls-files: ensure full index
grep: ensure full index
fsck: ensure full index
difftool: ensure full index
commit: ensure full index
checkout: ensure full index
...
Up until recently, object IDs did not have an algorithm member, only a
hash. Consequently, it was possible to share one null (all-zeros)
object ID among all hash algorithms. Now that we're going to be
handling objects from multiple hash algorithms, it's important to make
sure that all object IDs have a correct algorithm field.
Introduce a per-algorithm null OID, and add it to struct hash_algo.
Introduce a wrapper function as well, and use it everywhere we used to
use the null_oid constant.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Plug the ort merge backend throughout the rest of the system, and
start testing it as a replacement for the recursive backend.
* en/ort-readiness:
Add testing with merge-ort merge strategy
t6423: mark remaining expected failure under merge-ort as such
Revert "merge-ort: ignore the directory rename split conflict for now"
merge-recursive: add a bunch of FIXME comments documenting known bugs
merge-ort: write $GIT_DIR/AUTO_MERGE whenever we hit a conflict
t: mark several submodule merging tests as fixed under merge-ort
merge-ort: implement CE_SKIP_WORKTREE handling with conflicted entries
t6428: new test for SKIP_WORKTREE handling and conflicts
merge-ort: support subtree shifting
merge-ort: let renormalization change modify/delete into clean delete
merge-ort: have ll_merge() use a special attr_index for renormalization
merge-ort: add a special minimal index just for renormalization
merge-ort: use STABLE_QSORT instead of QSORT where required
Various rename detection optimization to help "ort" merge strategy
backend.
* en/ort-perf-batch-10:
diffcore-rename: determine which relevant_sources are no longer relevant
merge-ort: record the reason that we want a rename for a file
diffcore-rename: add computation of number of unknown renames
diffcore-rename: check if we have enough renames for directories early on
diffcore-rename: only compute dir_rename_count for relevant directories
merge-ort: record the reason that we want a rename for a directory
merge-ort, diffcore-rename: tweak dirs_removed and relevant_source type
diffcore-rename: take advantage of "majority rules" to skip more renames
versions could be an empty string_list. In that case, versions->items is
NULL, and we shouldn't be trying to perform pointer arithmetic with it (as
that results in undefined behaviour).
Moreover we only use the results of this calculation once when calling
QSORT. Therefore we choose to skip creating relevant_entries and call
QSORT directly with our manipulated pointers (but only if there's data
requiring sorting). This lets us avoid abusing the string_list API,
and saves us from having to explain why this abuse is OK.
Finally, an assertion is added to make sure that write_tree() is called
with a valid offset.
This issue has probably existed since:
ee4012dcf9 (merge-ort: step 2 of tree writing -- function to create tree object, 2020-12-13)
But it only started occurring during tests since tests started using
merge-ort:
f3b964a07e (Add testing with merge-ort merge strategy, 2021-03-20)
For reference - here's the original UBSAN commit that implemented this
check, it sounds like this behaviour isn't actually likely to cause any
issues (but we might as well fix it regardless):
https://reviews.llvm.org/D67122
UBSAN output from t3404 or t5601:
merge-ort.c:2669:43: runtime error: applying zero offset to null pointer
#0 0x78bb53 in write_tree merge-ort.c:2669:43
#1 0x7856c9 in process_entries merge-ort.c:3303:2
#2 0x782317 in merge_ort_nonrecursive_internal merge-ort.c:3744:2
#3 0x77feef in merge_incore_nonrecursive merge-ort.c:3853:2
#4 0x6f6a5c in do_recursive_merge sequencer.c:640:3
#5 0x6f6a5c in do_pick_commit sequencer.c:2221:9
#6 0x6ef055 in single_pick sequencer.c:4814:9
#7 0x6ef055 in sequencer_pick_revisions sequencer.c:4867:10
#8 0x4fb392 in run_sequencer revert.c:225:9
#9 0x4fa5b0 in cmd_revert revert.c:235:8
#10 0x42abd7 in run_builtin git.c:453:11
#11 0x429531 in handle_builtin git.c:704:3
#12 0x4282fb in run_argv git.c:771:4
#13 0x4282fb in cmd_main git.c:902:19
#14 0x524b63 in main common-main.c:52:11
#15 0x7fc2ca340349 in __libc_start_main (/lib64/libc.so.6+0x24349)
#16 0x4072b9 in _start start.S:120
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior merge-ort.c:2669:43 in
Signed-off-by: Andrzej Hunt <ajrhunt@google.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The ort merge backend has been optimized by skipping irrelevant
renames.
* en/ort-perf-batch-9:
diffcore-rename: avoid doing basename comparisons for irrelevant sources
merge-ort: skip rename detection entirely if possible
merge-ort: use relevant_sources to filter possible rename sources
merge-ort: precompute whether directory rename detection is needed
merge-ort: introduce wrappers for alternate tree traversal
merge-ort: add data structures for an alternate tree traversal
merge-ort: precompute subset of sources for which we need rename detection
diffcore-rename: enable filtering possible rename sources
Rename detection rework continues.
* en/ort-perf-batch-8:
diffcore-rename: compute dir_rename_guess from dir_rename_counts
diffcore-rename: limit dir_rename_counts computation to relevant dirs
diffcore-rename: compute dir_rename_counts in stages
diffcore-rename: extend cleanup_dir_rename_info()
diffcore-rename: move dir_rename_counts into dir_rename_info struct
diffcore-rename: add function for clearing dir_rename_count
Move computation of dir_rename_count from merge-ort to diffcore-rename
diffcore-rename: add a mapping of destination names to their indices
diffcore-rename: provide basic implementation of idx_possible_rename()
diffcore-rename: use directory rename guided basename comparisons
This reverts commit 5ced7c3da0, which was
put in place as a temporary measure to avoid optimizations unstably
erroring out on no destination having a majority of the necessary
renames for directories that had no new files and thus no need for
directory rename detection anyway. Now that optimizations are in place
to prevent us from trying to compute directory rename count computations
for directories that do not need it, we can undo this temporary measure.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There are a variety of questions users might ask while resolving
conflicts:
* What changes have been made since the previous (first) parent?
* What changes are staged?
* What is still unstaged? (or what is still conflicted?)
* What changes did I make to resolve conflicts so far?
The first three of these have simple answers:
* git diff HEAD
* git diff --cached
* git diff
There was no way to answer the final question previously. Adding one
is trivial in merge-ort, since it works by creating a tree representing
what should be written to the working copy complete with conflict
markers. Simply write that tree to .git/AUTO_MERGE, allowing users to
answer the fourth question with
* git diff AUTO_MERGE
I avoided using a name like "MERGE_AUTO", because that would be
merge-specific (much like MERGE_HEAD, REBASE_HEAD, REVERT_HEAD,
CHERRY_PICK_HEAD) and I wanted a name that didn't change depending on
which type of operation the merge was part of.
Ensure that paths which clean out other temporary operation-specific
files (e.g. CHERRY_PICK_HEAD, MERGE_MSG, rebase-merge/ state directory)
also clean out this AUTO_MERGE file.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When merge conflicts occur in paths removed by a sparse-checkout, we
need to unsparsify those paths (clear the SKIP_WORKTREE bit), and write
out the conflicted file to the working copy. In the very unlikely case
that someone manually put a file into the working copy at the location
of the SKIP_WORKTREE file, we need to avoid overwriting whatever edits
they have made and move that file to a different location first.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
merge-recursive has some simple code to support subtree shifting; copy
it over to merge-ort. This fixes t6409.12 under
GIT_TEST_MERGE_ALGORITHM=ort.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When we have a modify/delete conflict, but the only change to the
modification is e.g. change of line endings, then if renormalization is
requested then we should be able to recognize such a case as a
not-modified/delete and resolve the conflict automatically.
This fixes t6418.10 under GIT_TEST_MERGE_ALGORITHM=ort.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
ll_merge() needs an index when renormalization is requested. Create one
specifically for just this purpose with just the one needed entry. This
fixes t6418.4 and t6418.5 under GIT_TEST_MERGE_ALGORITHM=ort.
NOTE 1: Even if the user has a working copy or a real index (which is
not a given as merge-ort can be used in bare repositories), we
explicitly ignore any .gitattributes file from either of these
locations. merge-ort can be used to merge two branches that are
unrelated to HEAD, so .gitattributes from the working copy and current
index should not be considered relevant.
NOTE 2: Since we are in the middle of merging, there is a risk that
.gitattributes itself is conflicted...leaving us with an ill-defined
situation about how to perform the rest of the merge. It could be that
the .gitattributes file does not even exist on one of the sides of the
merge, or that it has been modified on both sides. If it's been
modified on both sides, it's possible that it could itself be merged
cleanly, though it's also possible that it only merges cleanly if you
use the right version of the .gitattributes file to drive the merge. It
gets kind of complicated. The only test we ever had that attempted to
test behavior in this area was seemingly unaware of the undefined
behavior, but knew the test wouldn't work for lack of attribute handling
support, marked it as test_expect_failure from the beginning, but
managed to fail for several reasons unrelated to attribute handling.
See commit 6f6e7cfb52 ("t6038: remove problematic test", 2020-08-03) for
details. So there are probably various ways to improve what
initialize_attr_index() picks in the case of a conflicted .gitattributes
but for now I just implemented something simple -- look for whatever
.gitattributes file we can find in any of the higher order stages and
use it.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
renormalize_buffer() requires an index_state, which is something that
merge-ort does not operate with. However, all the renormalization code
needs is an index with a .gitattributes file...plus a little bit of
setup. Create such an index, along with the deallocation and
attr_direction handling.
A subsequent commit will add a function to finish the initialization
of this index.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
rename/rename conflict handling depends on the fact that if both sides
renamed the same path, that the one on the MERGE_SIDE1 will appear first
in the combined diff_queue_struct passed to process_renames(). Since we
add all pairs from MERGE_SIDE1 to combined first, and then all pairs
from MERGE_SIDE2, and then sort based on filename, this will only be
true if the sort used is stable. This was found due to the fact that
Mac, unlike Linux, apparently has a system-defined qsort that is not
stable.
While we are at it, review the other callers of QSORT and add comments
about why they can remain as calls to QSORT instead of being modified
to call STABLE_QSORT.
Signed-off-by: Elijah Newren <newren@gmail.com>
Reviewed-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There are two different reasons we might want a rename for a file -- for
three-way content merging or as part of directory rename detection.
Record the reason. diffcore-rename will potentially be able to filter
some of the ones marked as needed only for directory rename detection,
if it can determine those directory renames based solely on renames
found via exact rename detection and basename-guided rename detection.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The previous commit can only be effective if we have a computation of
the number of paths under a given directory which are still have pending
renames, and expected this number to be recorded in the dir_rename_count
map under the key UNKNOWN_DIR. Add the code necessary to compute these
values.
Note that this change means dir_rename_count might have a directory
whose only entry (for UNKNOWN_DIR) was removed by the time merge-ort
goes to check it. To account for this, merge-ort needs to check for the
case where the max count is 0.
With this change we are now computing the necessary value for each
directory in dirs_removed, but are not using that value anywhere. The
next two commits will make use of the values stored in dirs_removed in
order to compute whether each relevant_source (that is needed only for
directory rename detection) has become unnecessary.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When one side of history renames a directory, and the other side of
history added files to the old directory, directory rename detection is
used to warn about the location of the added files so the user can
move them to the old directory or keep them with the new one.
This sets up three different types of directories:
* directories that had new files added to them
* directories underneath a directory that had new files added to them
* directories where no new files were added to it or any leading path
Save this information in dirs_removed; the next several commits will
make use of this information.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
As noted in the previous commit, we want to be able to take advantage of
the "majority rules" portion of directory rename detection to avoid
detecting more renames than necessary. However, for diffcore-rename to
take advantage of that, it needs to know whether a rename source file
was needed for just directory rename detection reasons, or if it is
wanted for potential three-way content merging. Modify relevant_sources
from a strset to a strintmap, so we can encode additional information.
We also modify dirs_removed from a strset to a strintmap at the same
time because trying to determine what files are needed for directory
rename detection will require us tracking a bit more information for
each directory.
This commit only changes the types of the two variables from strset to
strintmap; it does not actually store any special values yet and for now
only checks for presence of entries in the strintmap. Thus, the code is
functionally identical to how it behaved before. Future commits will
start associating values with each key for these two maps.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add and apply a semantic patch for converting code that open-codes
CALLOC_ARRAY to use it instead. It shortens the code and infers the
element size automatically.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diffcore_rename_extended() will do a bunch of setup, then check for
exact renames, then abort before inexact rename detection if there are
no more sources or destinations that need to be matched. It will
sometimes be the case, however, that either
* we start with neither any sources or destinations
* we start with no *relevant* sources
In the first of these two cases, the setup and exact rename detection
will be very cheap since there are 0 files to operate on. In the second
case, it is quite possible to have thousands of files with none of the
source ones being relevant. Avoid calling diffcore_rename_extended() or
even some of the setup before diffcore_rename_extended() when we can
determine that rename detection is unnecessary.
For the testcases mentioned in commit 557ac0350d ("merge-ort: begin
performance work; instrument with trace2_region_* calls", 2020-10-28),
this change improves the performance as follows:
Before After
no-renames: 6.003 s ± 0.048 s 5.708 s ± 0.111 s
mega-renames: 114.009 s ± 0.236 s 102.171 s ± 0.440 s
just-one-mega: 3.489 s ± 0.017 s 3.471 s ± 0.015 s
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The past several commits determined conditions when rename sources might
be needed, and filled a relevant_sources strset with those paths. Pass
these along to diffcore_rename_extended() to use to limit the sources
that we need to detect renames for.
For the testcases mentioned in commit 557ac0350d ("merge-ort: begin
performance work; instrument with trace2_region_* calls", 2020-10-28),
this change improves the performance as follows:
Before After
no-renames: 12.596 s ± 0.061 s 6.003 s ± 0.048 s
mega-renames: 130.465 s ± 0.259 s 114.009 s ± 0.236 s
just-one-mega: 3.958 s ± 0.010 s 3.489 s ± 0.017 s
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The point of directory rename detection is that if one side of history
renames a directory, and the other side adds new files under the old
directory, then the merge can move those new files into the new
directory. This leads to the following important observation:
* If the other side does not add any new files under the old
directory, we do not need to detect any renames for that directory.
Similarly, directory rename detection had an important requirement:
* If a directory still exists on one side of history, it has not been
renamed on that side of history. (See section 4 of t6423 or
Documentation/technical/directory-rename-detection.txt for more
details).
Using these two bits of information, we note that directory rename
detection is only needed in cases where (1) directories exist in the
merge base and on one side of history (i.e. dirmask == 3 or dirmask ==
5), and (2) where there is some new file added to that directory on the
side where it still exists (thus where the file has filemask == 2 or
filemask == 4, respectively). This has to be done in two steps, because
we have the dirmask when we are first considering the directory, and
won't get the filemasks for the files within it until we recurse into
that directory. So, we save
dir_rename_mask = dirmask - 1
when we hit a directory that is missing on one side, and then later look
for cases of
filemask == dir_rename_mask
One final note is that as soon as we hit a directory that needs
directory rename detection, we will need to detect renames in all
subdirectories of that directory as well due to the "majority rules"
decision when files are renamed into different directory hierarchies.
We arbitrarily use the special value of 0x07 to record when we've hit
such a directory.
The combination of all the above mean that we introduce a variable
named dir_rename_mask (couldn't think of a better name) which has one
of the following values as we traverse into a directory:
* 0x00: directory rename detection not needed
* 0x02 or 0x04: directory rename detection only needed if files added
* 0x07: directory rename detection definitely needed
We then pass this value through to add_pairs() so that it can mark
location_relevant as true only when dir_rename_mask is 0x07.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add traverse_trees_wrapper() and traverse_trees_wrapper_callback()
functions. The former runs traverse_trees() with info->fn set to
traverse_trees_wrapper_callback, in order to simply save all the entries
without processing or recursing into any of them. This step allows
extra computation to be done (e.g. checking some condition across all
files) that can be used later. Then, after that is completed, it
iterates over all the saved entries and calls the original info->fn
callback with the saved data.
Currently, this does nothing more than marginally slowing down the tree
traversal since we do not take advantage of the opportunity to compute
anything special in traverse_trees_wrapper_callback(), and thus the real
callback will be called identically as it would have been without this
extra wrapper. However, a subsequent commit will add some special
computation of some values that the real callback will be able to use.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In order to determine whether directory rename detection is needed, we
as a pre-requisite need a way to traverse through all the files in a
given tree before visiting any directories within that tree.
traverse_trees() only iterates through the entries in the order they
appear, so add some data structures that will store all the entries as
we iterate through them in traverse_trees(), which will allow us to
re-traverse them in our desired order.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
rename detection works by trying to pair all file deletions (or
"sources") with all file additions (or "destinations"), checking
similarity, and then marking the sufficiently similar ones as renames.
This can be expensive if there are many sources and destinations on a
given side of history as it results in an N x M comparison matrix.
However, there are many cases where we can compute in advance that
detecting renames for some of the sources provides no useful information
and thus that we can exclude those sources from the matrix.
To see why, first note that the merge machinery uses detected renames in
two ways:
* directory rename detection: when one side of history renames a
directory, and the other side of history adds new files to that
directory, we want to be able to warn the user about the need to
chose whether those new files stay in the old directory or move
to the new one.
* three-way content merging: in order to do three-way content merging
of files, we need three different file versions. If one side of
history renamed a file, then some of the content for the file is
found under a different path than in the merge base or on the
other side of history.
Add a simple testcase showing the two kinds of reasons renames are
relevant; it's a testcase that will only pass if we detect both kinds of
needed renames.
Other than the testcase added above, this commit concentrates just on
the three-way content merging; it will punt and mark all sources as
needed for directory rename detection, and leave it to future commits to
narrow that down more.
The point of three-way content merging is to reconcile changes made on
*both* sides of history. What if the file wasn't modified on both
sides? There are two possibilities:
* If it wasn't modified on the renamed side:
-> then we get to do exact rename detection, which is cheap.
* If it wasn't modified on the unrenamed side:
-> then detection of a rename for that source file is irrelevant
That latter claim might be surprising at first, so let's walk through a
case to show why rename detection for that source file is irrelevant.
Let's use two filenames, old.c & new.c, with the following abbreviated
object ids (and where the value '000000' is used to denote that the file
is missing in that commit):
old.c new.c
MERGE_BASE: 01d01d 000000
MERGE_SIDE1: 01d01d 000000
MERGE_SIDE2: 000000 5e1ec7
If the rename *isn't* detected:
then old.c looks like it was unmodified on one side and deleted on
the other and should thus be removed. new.c looks like a new file we
should keep as-is.
If the rename *is* detected:
then a three-way content merge is done. Since the version of the
file in MERGE_BASE and MERGE_SIDE1 are identical, the three-way merge
will produce exactly the version of the file whose abbreviated
object id is 5e1ec7. It will record that file at the path new.c,
while removing old.c from the directory.
Note that these two results are identical -- a single file named 'new.c'
with object id 5e1ec7. In other words, it doesn't matter if the rename
is detected in the case where the file is unmodified on the unrenamed
side.
Use this information to compute whether we need rename detection for
each source created in add_pair().
It's probably worth noting that there used to be a few other edge or
corner cases besides three-way content merges and directory rename
detection where lack of rename detection could have affected the result,
but those cases actually highlighted where conflict resolution methods
were not consistent with each other. Fixing those inconsistencies were
thus critically important to enabling this optimization. That work
involved the following:
* bringing consistency to add/add, rename/add, and rename/rename
conflict types, as done back in the topic merged at commit
ac193e0e0a ("Merge branch 'en/merge-path-collision'", 2019-01-04),
and further extended in commits 2a7c16c980 ("t6422, t6426: be more
flexible for add/add conflicts involving renames", 2020-08-10) and
e8eb99d4a6 ("t642[23]: be more flexible for add/add conflicts
involving pair renames", 2020-08-10)
* making rename/delete more consistent with modify/delete
as done in commits 1f3c9ba707 ("t6425: be more flexible with
rename/delete conflict messages", 2020-08-10) and 727c75b23f
("t6404, t6423: expect improved rename/delete handling in ort
backend", 2020-10-26)
Since the set of relevant_sources we compute has not yet been narrowed
down for directory rename detection, we do not pass it to
diffcore_rename_extended() yet. That will be done after subsequent
commits narrow down the list of relevant_sources needed for directory
rename detection reasons.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add the ability to diffcore_rename_extended() to allow external callers
to declare that they only need renames detected for a subset of source
files, and use that information to skip detecting renames for them.
There are two important pieces to this optimization that may not be
obvious at first glance:
* We do not require callers to just filter the filepairs out
to remove the non-relevant sources, because exact rename detection
is fast and when it finds a match it can remove both a source and a
destination whereas the relevant_sources filter can only remove a
source.
* We need to filter out the source pairs in a preliminary pass instead
of adding a
strset_contains(relevant_sources, one->path)
check within the nested matrix loop. The reason for that is if we
have 30k renames, doing 30k * 30k = 900M strset_contains() calls
becomes extraordinarily expensive and defeats the performance gains
from this change; we only want to do 30k such calls instead.
If callers pass NULL for relevant_sources, that is special cases to
treat all sources as relevant. Since all callers currently pass NULL,
this optimization does not yet have any effect. Subsequent commits will
have merge-ort compute a set of relevant_sources to restrict which
sources we detect renames for, and have merge-ort pass that set of
relevant_sources to diffcore_rename_extended().
A note about filtering order:
Some may be curious why we don't filter out irrelevant sources at the
same time we filter out exact renames. While that technically could be
done at this point, there are two reasons to defer it:
First, was to reinforce a lesson that was too easy to forget. As I
mentioned above, in the past I filtered irrelevant sources out before
exact rename checking, and then discovered that exact renames' ability
to remove both sources and destinations was an important consideration
and thus doing the filtering after exact rename checking would speed
things up. Then at some point I realized that basename matching could
also remove both sources and destinations, and decided to put irrelevant
source filtering after basename filtering. That slowed things down a
lot. But, despite learning about this important ordering, in later
restructuring I forgot and made the same mistake of putting the
filtering after basename guided rename detection again. So, I have this
series of patches structured to do the irrelevant filtering last to
start to show how much extra it costs, and then add relevant filtering
in to find_basename_matches() to show how much it speeds things up.
Basically, it's a way to reinforce something that apparently was too
easy to forget, and make sure the commit messages record this lesson.
Second, the items in the "relevant_sources" in this patch series will
include all sources that *might be* relevant. It has to be conservative
and catch anything that might need a rename, but in the patch series
after this one we'll find ways to weed out more of the *might be*
relevant ones. Unfortunately, merge-ort does not have sufficient
information to weed those ones out, and there isn't enough information
at the time of filtering exact renames out to remove the extra ones
either. It has to be deferred. So the deferral is in part to simplify
some later additions.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Junio C Hamano
Ævar Arnfjörð Bjarmason
Elijah Newren
Alex Henrie
brian m. carlson
Andrzej Hunt
René Scharfe