The focus here is on adding a path_msg() which will queue up
warning/conflict/notice messages about the merge for later processing,
storing these in a pathname -> strbuf map. It might seem like a big
change, but it really just is:
* declaration of necessary map with some comments
* initialization and recording of data
* a bunch of code to iterate over the map at print/free time
* at least one caller in order to avoid an error about having an
unused function (which we provide in the form of implementing
modify/delete conflict handling).
At this stage, it is probably not clear why I am opting for delayed
output processing. There are multiple reasons:
1. Merges are supposed to abort if they would overwrite dirty changes
in the working tree. We cannot correctly determine whether changes
would be overwritten until both rename detection has occurred and
full processing of entries with the renames has finalized.
Warning/conflict/notice messages come up at intermediate codepaths
along the way, so unless we want spurious conflict/warning messages
being printed when the merge will be aborted anyway, we need to
save these messages and only print them when relevant.
2. There can be multiple messages for a single path, and we want all
messages for a give path to appear together instead of having them
grouped by conflict/warning type. This was a problem already with
merge-recursive.c but became even more important due to the
splitting apart of conflict types as discussed in the commit
message for 1f3c9ba707 ("t6425: be more flexible with rename/delete
conflict messages", 2020-08-10)
3. Some callers might want to avoid showing the output in certain
cases, such as if the end result is a clean merge. Rebases have
typically done this.
4. Some callers might not want the output to go to stdout or even
stderr, but might want to do something else with it entirely.
For example, a --remerge-diff option to `git show` or `git log
-p` that remerges on the fly and diffs merge commits against the
remerged version would benefit from stdout/stderr not being
written to in the standard form.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This simplistic and weird-looking patch is here to facilitate future
patch submissions. Adding this stub allows rename detection code to
reference it in one patch series, while a separate patch series can
define the implementation, and then both series can merge cleanly and
work nicely together at that point.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Commit b658536f59 ("merge-ort: add some high-level algorithm structure",
2020-10-27) added high-level structure of the ort merge algorithm. As
we have added more and more functions, that high-level structure has
been slightly obscured. Since functions are still grouped according to
this high-level structure, add comments denoting sections where all the
functions are specifically tied to a piece of the high-level structure.
This function groupings include a few sub-divisions of the original
high-level structure, including some sub-divisions that are yet to be
submitted. Each has (or will have) several functions all serving as
helpers to one or two main functions for each section.
As an added bonus, the comments will serve to provide a small textual
separation between nearby sections and allow the next three patch series
to be submitted independently and merge cleanly.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This field will be used in future patches to allow removal of paths from
opt->priv->paths.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This field is not yet used, but will be used by both the rename handling
code, and the conflict type handling code in process_entry().
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move most of merge_finalize() into a new helper function,
clear_internal_opts(). This is a step to facilitate recursive merges,
as well as some future optimizations.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Include blob.h for definition of blob_type, and commit-reach.h for
declarations of get_merge_bases() and in_merge_bases(). While none of
these are used yet, we want to avoid cross-dependencies in the next
three series of patches for merge-ort and merge them at the end; adding
these "#include"s now avoids textual conflicts.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
After checkout(), the working tree has the appropriate contents, and the
index matches the working copy. That means that all unmodified and
cleanly merged files have correct index entries, but conflicted entries
need to be updated.
We do this by looping over the conflicted entries, marking the existing
index entry for the path with CE_REMOVE, adding new higher order staged
for the path at the end of the index (ignoring normal index sort order),
and then at the end of the loop removing the CE_REMOVED-marked cache
entries and sorting the index.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Since merge-ort creates a tree for its output, when there are no
conflicts, updating the working tree and index is as simple as using the
unpack_trees() machinery with a twoway_merge (i.e. doing the equivalent
of a "checkout" operation).
If there were conflicts in the merge, then since the tree we created
included all the conflict markers, then using the unpack_trees machinery
in this manner will still update the working tree correctly. Further,
all index entries corresponding to cleanly merged files will also be
updated correctly by this procedure. Index entries corresponding to
conflicted entries will appear as though the user had run "git add -u"
after the merge to accept all files as-is with conflict markers.
Thus, after running unpack_trees(), there needs to be a separate step
for updating the entries in the index corresponding to conflicted files.
This will be the job for the function record_conflicted_index_entris(),
which will be implemented in a subsequent commit.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This adds a basic implementation for merge_switch_to_result(), though
just in terms of a few new empty functions that will be defined in
subsequent commits.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Our order for processing of entries means that if we have a tree of
files that looks like
Makefile
src/moduleA/foo.c
src/moduleA/bar.c
src/moduleB/baz.c
src/moduleB/umm.c
tokens.txt
Then we will process paths in the order of the leftmost column below. I
have added two additional columns that help explain the algorithm that
follows; the 2nd column is there to remind us we have oid & mode info we
are tracking for each of these paths (which differs between the paths
which I'm not representing well here), and the third column annotates
the parent directory of the entry:
tokens.txt <version_info> ""
src/moduleB/umm.c <version_info> src/moduleB
src/moduleB/baz.c <version_info> src/moduleB
src/moduleB <version_info> src
src/moduleA/foo.c <version_info> src/moduleA
src/moduleA/bar.c <version_info> src/moduleA
src/moduleA <version_info> src
src <version_info> ""
Makefile <version_info> ""
When the parent directory changes, if it's a subdirectory of the previous
parent directory (e.g. "" -> src/moduleB) then we can just keep appending.
If the parent directory differs from the previous parent directory and is
not a subdirectory, then we should process that directory.
So, for example, when we get to this point:
tokens.txt <version_info> ""
src/moduleB/umm.c <version_info> src/moduleB
src/moduleB/baz.c <version_info> src/moduleB
and note that the next entry (src/moduleB) has a different parent than
the last one that isn't a subdirectory, we should write out a tree for it
100644 blob <HASH> umm.c
100644 blob <HASH> baz.c
then pop all the entries under that directory while recording the new
hash for that directory, leaving us with
tokens.txt <version_info> ""
src/moduleB <new version_info> src
This process repeats until at the end we get to
tokens.txt <version_info> ""
src <new version_info> ""
Makefile <version_info> ""
and then we can write out the toplevel tree. Since we potentially have
entries in our string_list corresponding to multiple different toplevel
directories, e.g. a slightly different repository might have:
whizbang.txt <version_info> ""
tokens.txt <version_info> ""
src/moduleD <new version_info> src
src/moduleC <new version_info> src
src/moduleB <new version_info> src
src/moduleA/foo.c <version_info> src/moduleA
src/moduleA/bar.c <version_info> src/moduleA
When src/moduleA is popped off, we need to know that the "last
directory" reverts back to src, and how many entries in our string_list
are associated with that parent directory. So I use an auxiliary
offsets string_list which would have (parent_directory,offset)
information of the form
"" 0
src 2
src/moduleA 5
Whenever I write out a tree for a subdirectory, I set versions.nr to
the final offset value and then decrement offsets.nr...and then add
an entry to versions with a hash for the new directory.
The idea is relatively simple, there's just a lot of accounting to
implement this.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Create a new function, write_tree(), which will take a list of
basenames, modes, and oids for a single directory and create a tree
object in the object-store. We do not yet have just basenames, modes,
and oids for just a single directory (we have a mixture of entries from
all directory levels in the hierarchy) so we still die() before the
current call to write_tree(), but the next patch will rectify that.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
As a step towards transforming the processed path->conflict_info entries
into an actual tree object, start recording basenames, modes, and oids
in a dir_metadata structure. Subsequent commits will make use of this
to actually write a tree.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We want to handle paths below a directory before needing to handle the
directory itself. Also, we want to handle the directory immediately
after the paths below it, so we can't use simple lexicographic ordering
from strcmp (which would insert foo.txt between foo and foo/file.c).
Copy string_list_df_name_compare() from merge-recursive.c, and set up a
string list of paths sorted by that function so that we can iterate in
the desired order.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a process_entries() implementation that just loops over the paths
and processes each one individually with an auxiliary process_entry()
call. Add a basic process_entry() as well, which handles several cases
but leaves a few of the more involved ones with die-not-implemented
messages. Also, although process_entries() is supposed to create a
tree, it does not yet have code to do so -- except in the special case
of merging completely empty trees.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When all three trees have the same oid, there is no need to recurse into
these trees to find that all files within them happen to match. We can
just record any one of the trees as the resolution of merging that
particular path.
Immediately resolving trees for other types of trivial tree merges (such
as one side matches the merge base, or the two sides match each other)
would prevent us from detecting renames for some paths, and thus prevent
us from doing three-way content merges for those paths whose renames we
did not detect.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Create a helper function, setup_path_info(), which can be used to record
all the information we want in a merged_info or conflict_info. While
there is currently only one caller of this new function, and some of its
particular parameters are fixed, future callers of this function will be
added later.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Three-way merges, by their nature, are going to often have two or more
trees match at a given subdirectory. We can avoid calling
fill_tree_descriptor() on the same tree by checking when these trees
match. Noting when various oids match will also be useful in other
calculations and optimizations as well.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This does not actually collect any necessary info other than the
pathnames involved, since it just allocates an all-zero conflict_info
and stuffs that into paths. However, it invokes the traverse_trees()
machinery to walk over all the paths and sets up the basic
infrastructure we need.
I have left out a few obvious optimizations to try to make this patch as
short and obvious as possible. A subsequent patch will add some of
those back in with some more useful data fields before we introduce a
patch that actually sets up the conflict_info fields.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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>
In my cursory investigation, histogram diffs are about 2% slower than
Myers diffs. Others have probably done more detailed benchmarks. But,
in short, histogram diffs have been around for years and in a number of
cases provide obviously better looking diffs where Myers diffs are
unintelligible but the performance hit has kept them from becoming the
default.
However, there are real merge bugs we know about that have triggered on
git.git and linux.git, which I don't have a clue how to address without
the additional information that I believe is provided by histogram
diffs. See the following:
https://lore.kernel.org/git/20190816184051.GB13894@sigill.intra.peff.net/https://lore.kernel.org/git/CABPp-BHvJHpSJT7sdFwfNcPn_sOXwJi3=o14qjZS3M8Rzcxe2A@mail.gmail.com/https://lore.kernel.org/git/CABPp-BGtez4qjbtFT1hQoREfcJPmk9MzjhY5eEq1QhXT23tFOw@mail.gmail.com/
I don't like mismerges. I really don't like silent mismerges. While I
am sometimes willing to make performance and correctness tradeoff, I'm
much more interested in correctness in general. I want to fix the above
bugs. I have not yet started doing so, but I believe histogram diff at
least gives me an angle. Unfortunately, I can't rely on using the
information from histogram diff unless it's in use. And it hasn't been
used because of a few percentage performance hit.
In testcases I have looked at, merge-ort is _much_ faster than
merge-recursive for non-trivial merges/rebases/cherry-picks. As such,
this is a golden opportunity to switch out the underlying diff algorithm
(at least the one used by the merge machinery; git-diff and git-log are
separate questions); doing so will allow me to get additional data and
improved diffs, and I believe it will help me fix the above bugs at some
point in the future.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
merge_start() basically does a bunch of sanity checks, then allocates
and initializes opt->priv -- a struct merge_options_internal.
Most of the sanity checks are usable as-is. The
allocation/intialization is a bit different since merge-ort has a very
different merge_options_internal than merge-recursive, but the idea is
the same.
The weirdest part here is that merge-ort and merge-recursive use the
same struct merge_options, even though merge_options has a number of
fields that are oddly specific to merge-recursive's internal
implementation and don't even make sense with merge-ort's high-level
design (e.g. buffer_output, which merge-ort has to always do). I reused
the same data structure because:
* most the fields made sense to both merge algorithms
* making a new struct would have required making new enums or somehow
externalizing them, and that was getting messy.
* it simplifies converting the existing callers by not having to
have different code paths for merge_options setup.
I also marked detect_renames as ignored. We can revisit that later, but
in short: merge-recursive allowed turning off rename detection because
it was sometimes glacially slow. When you speed something up by a few
orders of magnitude, it's worth revisiting whether that justification is
still relevant. Besides, if folks find it's still too slow, perhaps
they have a better scaling case than I could find and maybe it turns up
some more optimizations we can add. If it still is needed as an option,
it is easy to add later.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
merge_ort_nonrecursive_internal() will be used by both
merge_inmemory_nonrecursive() and merge_inmemory_recursive(); let's
focus on it for now. It involves some setup -- merge_start() --
followed by the following chain of functions:
collect_merge_info()
This function will populate merge_options_internal's paths field,
via a call to traverse_trees() and a new callback that will be added
later.
detect_and_process_renames()
This function will detect renames, and then adjust entries in paths
to move conflict stages from old pathnames into those for new
pathnames, so that the next step doesn't have to think about renames
and just can do three-way content merging and such.
process_entries()
This function determines how to take the various stages (versions of
a file from the three different sides) and merge them, and whether
to mark the result as conflicted or cleanly merged. It also writes
out these merged file versions as it goes to create a tree.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Set up some basic internal data structures. The only carry-over from
merge-recursive.c is call_depth, though needed_rename_limit will be
added later.
The central piece of data will definitely be the strmap "paths", which
will map every relevant pathname under consideration to either a
merged_info or a conflict_info. ("conflicted" is a strmap that is a
subset of "paths".)
merged_info contains all relevant information for a non-conflicted
entry. conflict_info contains a merged_info, plus any additional
information about a conflict such as the higher orders stages involved
and the names of the paths those came from (handy once renames get
involved). If an entry remains conflicted, the merged_info portion of a
conflict_info will later be filled with whatever version of the file
should be placed in the working directory (e.g. an as-merged-as-possible
variation that contains conflict markers).
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* en/strmap:
shortlog: use strset from strmap.h
Use new HASHMAP_INIT macro to simplify hashmap initialization
strmap: take advantage of FLEXPTR_ALLOC_STR when relevant
strmap: enable allocations to come from a mem_pool
strmap: add a strset sub-type
strmap: split create_entry() out of strmap_put()
strmap: add functions facilitating use as a string->int map
strmap: enable faster clearing and reusing of strmaps
strmap: add more utility functions
strmap: new utility functions
hashmap: provide deallocation function names
hashmap: introduce a new hashmap_partial_clear()
hashmap: allow re-use after hashmap_free()
hashmap: adjust spacing to fix argument alignment
hashmap: add usage documentation explaining hashmap_free[_entries]()
Now that hashamp has lazy initialization and a HASHMAP_INIT macro,
hashmaps allocated on the stack can be initialized without a call to
hashmap_init() and in some cases makes the code a bit shorter. Convert
some callsites over to take advantage of this.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
By default, we do not use a mempool and strdup_strings is true; in this
case, we can avoid both an extra allocation and an extra free by just
over-allocating for the strmap_entry leaving enough space at the end to
copy the key. FLEXPTR_ALLOC_STR exists for exactly this purpose, so
make use of it.
Also, adjust the case when we are using a memory pool and strdup_strings
is true to just do one allocation from the memory pool instead of two so
that the strmap_clear() and strmap_remove() code can just avoid freeing
the key in all cases.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
For heavy users of strmaps, allowing the keys and entries to be
allocated from a memory pool can provide significant overhead savings.
Add an option to strmap_init_with_options() to specify a memory pool.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Similar to adding strintmap for special-casing a string -> int mapping,
add a strset type for cases where we really are only interested in using
strmap for storing a set rather than a mapping. In this case, we'll
always just store NULL for the value but the different struct type makes
it clearer than code comments how a variable is intended to be used.
The difference in usage also results in some differences in API: a few
things that aren't necessary or meaningful are dropped (namely, the
free_values argument to *_clear(), and the *_get() function), and
strset_add() is chosen as the API instead of strset_put().
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This will facilitate adding entries to a strmap subtype in ways that
differ slightly from that of strmap_put().
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Although strmap could be used as a string->int map, one either had to
allocate an int for every entry and then deallocate later, or one had to
do a bunch of casting between (void*) and (intptr_t).
Add some special functions that do the casting. Also, rename put->set
for such wrapper functions since 'put' implied there may be some
deallocation needed if the string was already found in the map, which
isn't the case when we're storing an int value directly in the void*
slot instead of using the void* slot as a pointer to data.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When strmaps are used heavily, such as is done by my new merge-ort
algorithm, and strmaps need to be cleared but then re-used (because of
e.g. picking multiple commits to cherry-pick, or due to a recursive
merge having several different merges while recursing), free-ing and
reallocating map->table repeatedly can add up in time, especially since
it will likely be reallocated to a much smaller size but the previous
merge provides a good guide to the right size to use for the next merge.
Introduce strmap_partial_clear() to take advantage of this type of
situation; it will act similar to strmap_clear() except that
map->table's entries are zeroed instead of map->table being free'd.
Making use of this function reduced the cost of
clear_or_reinit_internal_opts() by about 20% in mert-ort, and dropped
the overall runtime of my rebase testcase by just under 2%.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This adds a number of additional convienence functions I want/need:
* strmap_get_size()
* strmap_empty()
* strmap_remove()
* strmap_for_each_entry()
* strmap_get_entry()
I suspect the first four are self-explanatory.
strmap_get_entry() is similar to strmap_get() except that instead of just
returning the void* value that the string maps to, it returns the
strmap_entry that contains both the string and the void* value (or
NULL if the string isn't in the map). This is helpful because it avoids
multiple lookups, e.g. in some cases a caller would need to call:
* strmap_contains() to check that the map has an entry for the string
* strmap_get() to get the void* value
* <do some work to update the value>
* strmap_put() to update/overwrite the value
If the void* pointer returned really is a pointer, then the last step is
unnecessary, but if the void* pointer is just cast to an integer then
strmap_put() will be needed. In contrast, one can call strmap_get_entry()
and then:
* check if the string was in the map by whether the pointer is NULL
* access the value via entry->value
* directly update entry->value
meaning that we can replace two or three hash table lookups with one.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Allow the testsuite to run where it treats requests for "recursive" or
the default merge algorithm via consulting the environment variable
GIT_TEST_MERGE_ALGORITHM which is expected to either be "recursive" (the
old traditional algorithm) or "ort" (the new algorithm).
Also, allow folks to pick the new algorithm via config setting. It
turns out builtin/merge.c already had a way to allow users to specify a
different default merge algorithm: pull.twohead. Rather odd
configuration name (especially to be in the 'pull' namespace rather than
'merge') but it's there. Add that same configuration to rebase,
cherry-pick, and revert.
This required updating the various callsites that called merge_trees()
or merge_recursive() to conditionally call the new API, so this serves
as another demonstration of what the new API looks and feels like.
There are almost certainly some callsites that have not yet been
modified to work with the new merge algorithm, but this represents the
ones that I have been testing with thus far.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add strmap as a new struct and associated utility functions,
specifically for hashmaps that map strings to some value. The API is
taken directly from Peff's proposal at
https://lore.kernel.org/git/20180906191203.GA26184@sigill.intra.peff.net/
Note that similar string-list, I have a strdup_strings setting.
However, unlike string-list, strmap_init() does not take a parameter for
this setting and instead automatically sets it to 1; callers who want to
control this detail need to instead call strmap_init_with_options().
(Future patches will add additional parameters to
strmap_init_with_options()).
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
hashmap_free(), hashmap_free_entries(), and hashmap_free_() have existed
for a while, but aren't necessarily the clearest names, especially with
hashmap_partial_clear() being added to the mix and lazy-initialization
now being supported. Peff suggested we adopt the following names[1]:
- hashmap_clear() - remove all entries and de-allocate any
hashmap-specific data, but be ready for reuse
- hashmap_clear_and_free() - ditto, but free the entries themselves
- hashmap_partial_clear() - remove all entries but don't deallocate
table
- hashmap_partial_clear_and_free() - ditto, but free the entries
This patch provides the new names and converts all existing callers over
to the new naming scheme.
[1] https://lore.kernel.org/git/20201030125059.GA3277724@coredump.intra.peff.net/
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
merge-ort is a heavy user of strmaps, which are built on hashmap.[ch].
clear_or_reinit_internal_opts() in merge-ort was taking about 12% of
overall runtime in my testcase involving rebasing 35 patches of
linux.git across a big rename. clear_or_reinit_internal_opts() was
calling hashmap_free() followed by hashmap_init(), meaning that not only
was it freeing all the memory associated with each of the strmaps just
to immediately allocate a new array again, it was allocating a new array
that was likely smaller than needed (thus resulting in later need to
rehash things). The ending size of the map table on the previous commit
was likely almost perfectly sized for the next commit we wanted to pick,
and not dropping and reallocating the table immediately is a win.
Add some new API to hashmap to clear a hashmap of entries without
freeing map->table (and instead only zeroing it out like alloc_table()
would do, along with zeroing the count of items in the table and the
shrink_at field).
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Previously, once map->table had been freed, any calls to hashmap_put(),
hashmap_get(), or hashmap_remove() would cause a NULL pointer
dereference (since hashmap_free_() also zeros the memory; without that
zeroing, calling these functions would cause a use-after-free problem).
Modify these functions to check for a NULL table and automatically
allocate as needed.
Also add a HASHMAP_INIT(fn, data) macro for initializing hashmaps on the
stack without calling hashmap_init().
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add a new test-tool command named 'fast-rebase', which is a
super-slimmed down and nowhere near as capable version of 'git rebase'.
'test-tool fast-rebase' is not currently planned for usage in the
testsuite, but is here for two purposes:
1) Demonstrate the desired API of merge-ort. In particular,
fast-rebase takes advantage of the separation of the merging
operation from the updating of the index and working tree, to
allow it to pick N commits, but only update the index and working
tree once at the end. Look for the calls to
merge_incore_nonrecursive() and merge_switch_to_result().
2) Provide a convenient benchmark that isn't polluted by the heavy
disk writing and forking of unnecessary processes that comes from
sequencer.c and merge-recursive.c. fast-rebase is not meant to
replace sequencer.c, just give ideas on how sequencer.c can be
changed. Updating sequencer.c with these goals is probably a
large amount of work; writing a simple targeted command with
no documentation, less-than-useful help messages, numerous
limitations in terms of flags it can accept and situations it can
handle, and which is flagged off from users is a much easier
interim step.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There are a few differences between the new API in merge-ort and the old
API in merge-recursive. While the new API is more flexible, it might
feel like more work at times than the old API. merge-ort-wrappers
creates two convenience wrappers taking the exact same arguments as the
old merge_trees() and merge_recursive() functions and implements them
via the new API. This makes converting existing callsites easier, and
serves to highlight some of the differences in the API.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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>
Elijah Newren
Junio C Hamano