The most expensive part of packing a repository for transport to
another system is enumerating all of the objects in the repository.
Once this gets to the size of the linux-2.6 repository (1.8 million
objects), enumeration can take several CPU minutes and costs a lot
of temporary working set memory.
Teach PackWriter to efficiently reuse an existing "cached pack"
by answering a clone request with a thin pack followed by a larger
cached pack appended to the end. This requires the repository
owner to first construct the cached pack by hand, and record the
tip commits inside of $GIT_DIR/objects/info/cached-packs:
cd $GIT_DIR
root=$(git rev-parse master)
tmp=objects/.tmp-$$
names=$(echo $root | git pack-objects --keep-true-parents --revs $tmp)
for n in $names; do
chmod a-w $tmp-$n.pack $tmp-$n.idx
touch objects/pack/pack-$n.keep
mv $tmp-$n.pack objects/pack/pack-$n.pack
mv $tmp-$n.idx objects/pack/pack-$n.idx
done
(echo "+ $root";
for n in $names; do echo "P $n"; done;
echo) >>objects/info/cached-packs
git repack -a -d
When a clone request needs to include $root, the corresponding
cached pack will be copied as-is, rather than enumerating all of
the objects that are reachable from $root.
For a linux-2.6 kernel repository that should be about 376 MiB,
the above process creates two packs of 368 MiB and 38 MiB[1].
This is a local disk usage increase of ~26 MiB, due to reduced
delta compression between the large cached pack and the smaller
recent activity pack. The overhead is similar to 1 full copy of
the compressed project sources.
With this cached pack in hand, JGit daemon completes a clone request
in 1m17s less time, but a slightly larger data transfer (+2.39 MiB):
Before:
remote: Counting objects: 1861830, done
remote: Finding sources: 100% (1861830/1861830)
remote: Getting sizes: 100% (88243/88243)
remote: Compressing objects: 100% (88184/88184)
Receiving objects: 100% (1861830/1861830), 376.01 MiB | 19.01 MiB/s, done.
remote: Total 1861830 (delta 4706), reused 1851053 (delta 1553844)
Resolving deltas: 100% (1564621/1564621), done.
real 3m19.005s
After:
remote: Counting objects: 1601, done
remote: Counting objects: 1828460, done
remote: Finding sources: 100% (50475/50475)
remote: Getting sizes: 100% (18843/18843)
remote: Compressing objects: 100% (7585/7585)
remote: Total 1861830 (delta 2407), reused 1856197 (delta 37510)
Receiving objects: 100% (1861830/1861830), 378.40 MiB | 31.31 MiB/s, done.
Resolving deltas: 100% (1559477/1559477), done.
real 2m2.938s
Repository owners can periodically refresh their cached packs by
repacking their repository, folding all newer objects into a larger
cached pack. Since repacking is already considered to be a normal
Git maintenance activity, this isn't a very big burden.
[1] In this test $root was set back about two weeks.
Change-Id: Ib87131d5c4b5e8c5cacb0f4fe16ff4ece554734b
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
CGit pack-objects displays a totals line after the pack data
was fully written. This can be useful to understand some of
the decisions made by the packer, and has been a great tool
for helping to debug some of that code.
Track some of the basic values, and send it to the client when
packing is done:
remote: Counting objects: 1826776, done
remote: Finding sources: 100% (55121/55121)
remote: Getting sizes: 100% (25654/25654)
remote: Compressing objects: 100% (11434/11434)
remote: Total 1861830 (delta 3926), reused 1854705 (delta 38306)
Receiving objects: 100% (1861830/1861830), 386.03 MiB | 30.32 MiB/s, done.
Change-Id: If3b039017a984ed5d5ae80940ce32bda93652df5
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
The first 'Compressing objects' progress message is wrong, its
actually PackWriter looking up the sizes of each object in the
ObjectDatabase, so objects can be sorted correctly in the later
type-size sort that tries to take advantage of "Linus' Law" to
improve delta compression.
Rename the progress to say 'Getting sizes', which is an accurate
description of what it is doing.
Change-Id: Ida0a052ad2f6e994996189ca12959caab9e556a3
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
After consulting with Christian Halstrick, it turned out that the
handling of rebase during pull was implemented incorrectly.
Change-Id: I40f03409e080cdfeceb21460150f5e02a016e7f4
Signed-off-by: Mathias Kinzler <mathias.kinzler@sap.com>
Introduce metaData compare between working tree and index entries
Instead of offering only a high-level isModified() method a new
method compareMetadata() is introduced which compares a working tree entry
and a index entry by looking at metadata only. Some use-cases
(e.g. computing the content-id in idBuffer()) may use this new method
instead of isModified().
Change-Id: I4de7501d159889fbac5ae6951f4fef8340461b47
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
The java.io.File.createNewFile() method for creating new empty files
reports failure by returning false. To ease proper checking of return
values provide a utility method wrapping createNewFile() throwing
IOException on failure.
Change-Id: I42a3dc9d8ff70af62e84de396e6a740050afa896
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Merging Git notes branches has several differences from merging "normal"
branches. Although Git notes are initially stored as one flat tree the
tree may fanout when the number of notes becomes too large for efficient
access. In this case the first two hex digits of the note name will be
used as a subdirectory name and the rest 38 hex digits as the file name
under that directory. Similarly, when number of notes decreases a fanout
tree may collapse back into a flat tree. The Git notes merge algorithm
must take into account possibly different tree structures in different
note branches and must properly match them against each other.
Any conflict on a Git note is, by default, resolved by concatenating
the two conflicting versions of the note. A delete-edit conflict is, by
default, resolved by keeping the edit version.
The note merge logic is pluggable and the caller may provide custom
note merger that will perform different merging strategy.
Additionally, it is possible to have non-note entries inside a notes
tree. The merge algorithm must also take this fact into account and
will try to merge such non-note entries. However, in case of any merge
conflicts the merge operation will fail. Git notes merge algorithm is
currently not trying to do content merge of non-note entries.
Thanks to Shawn Pearce for patiently answering my questions related to
this topic, giving hints and providing code snippets.
Change-Id: I3b2335c76c766fd7ea25752e54087f9b19d69c88
Signed-off-by: Sasa Zivkov <sasa.zivkov@sap.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
This is almost reverted cherry-pick, and the implementation is
almost identical. It orders the input to merge differently to get
the effect and produces a different commit message with the
default author, rather than the original author.
Change-Id: I39970091d9f7406ae7168b8efaab23a5e2c16bad
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>
Add support for getting the system wide configuration
These settings are stored in <prefix>/etc/gitconfig. The C Git
binary is installed in <prefix>/bin, so we look for the C Git
executable to find this location, first by looking at the PATH
environment variable and then by attemting to launch bash as
a login shell to find out.
Bug: 333216
Change-Id: I1bbee9fb123a81714a34a9cc242b92beacfbb4a8
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>
The java.io.File methods for creating directories report failure by
returning false. To ease proper checking of return values provide
utility methods wrapping mkdir() and mkdirs() which throw IOException
on failure.
Also fix the tests to store test data under a trash folder and cleanup
after test.
Change-Id: I09c7f9909caf7e25feabda9d31e21ce154e7fcd5
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
For --continue, the Rebase command asserts that there are no unmerged
paths in the current repository. Then it checks if a commit is needed.
If yes, the commit message and author are taken from the author_script
and message files, respectively, and a commit is performed before the
next step is applied.
For --skip, the workspace is reset to the current HEAD before applying
the next step.
Includes some tests and a refactoring that extracts Strings in the
code into constants.
Change-Id: I72d9968535727046e737ec20e23239fe79976179
Signed-off-by: Mathias Kinzler <mathias.kinzler@sap.com>
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Provide file helper methods in a reusable utility class to
replace many local implementations. java.io.File has some
methods reporting failure by returning false. We prefer to
throw IOException on failure so that callers can't forget
checking the return value.
Change-Id: I430c77b5d2cffcf8b47584326ad4817a7291845e
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Add more tests for rebase and externalized missing Strings
Coverage tests showed that we are missing to test certain areas
in the rebase command. Add the missing tests.
Change-Id: Ia4a272d26cde7e1861dac30496e4b6799fc8187a
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Add the ability to checkout a branch to the working tree.
Bug: 330860
Change-Id: Ie06b9e799a9e1be384da0b8996efa7209b32eac3
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
This is a first iteration to implement Rebase. At the moment, this
does not implement --continue and --skip, so if the first
conflict is found, the only option is to --abort the command.
Bug: 328217
Change-Id: I24d60c0214e71e5572955f8261e10a42e9e95298
Signed-off-by: Mathias Kinzler <mathias.kinzler@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
Enable providing credentials for HTTP authentication
This change is based on http://egit.eclipse.org/r/#change,1652
by David Green. The change adds the concept of a CredentialsProvider
which can be registered for git transports and which is
responsible to return credential-related data like passwords and
usernames. Whenenver the transports detects that an authentication
with certain credentials has to be done it will ask the
CredentialsProvider for this data. Foreseen implementations for
such a Provider may be a EGitCredentialsProvider (caching
credential data entered e.g. in the Clone-Wizzard) or a NetRcProvider
(gathering data out of ~/.netrc file).
Bug: 296201
Change-Id: Ibe13e546b45eed3e193c09ecb414bbec2971d362
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Stefan Lay <stefan.lay@sap.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
CC: David Green <dgreen99@gmail.com>
PullCommand: support upstream configuration for local branches
When creating a local branch based on another local branch, the
upstream configuration contains "." as origin and the source branch
as "merge". The PullCommand should support this by skipping the
fetch step altogether and use the base branch to merge with.
Change-Id: I260a1771aeeffca5b0161d1494fd63c672ecc2a6
Signed-off-by: Mathias Kinzler <mathias.kinzler@sap.com>
Implemented the initial version of a cherry-pick command.
A correct error handling is missing (what happens if the
checkout fails, the cherry-pick leads to conflicts etc).
But straightforward cherry-picks works.
Change-Id: I235c0eb3a7a2d5bdfe40400f1deed06f29d746e1
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
The need for branching becomes more pressing with pull
support: we need to make sure the upstream configuration entries
are written correctly when creating and renaming branches
(and of course are cleaned up when deleting them).
This adds support for listing, adding, deleting and renaming
branches including the more common options.
Bug: 326938
Change-Id: I00bcc19476e835d6fd78fd188acde64946c1505c
Signed-off-by: Mathias Kinzler <mathias.kinzler@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
This is the minimal implementation of a "Pull" command. It does not
have any parameters besides the generic progress monitor and timeout.
It works on the currently checked-out branch and assumes that the
configuration contains the keys "branch.<branch name>.remote" and
"branch.<branch name>.merge" to determine the remote configuration
for the fetch and the remote branch name for the merge.
Bug: 303404
Change-Id: I7fe09029996d0cfc09a7d8f097b5d6af1488fa93
Signed-off-by: Mathias Kinzler <mathias.kinzler@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
Some strings were not externalized. Also use them in HTTP tests to
ensure that they will also succeed when message bundles are
translated.
Change-Id: Id02717176557e7d57e676e1339cd89f2be88d330
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Increase core.streamFileThreshold default to 50 MiB
Projects like org.eclipse.mdt contain large XML files about 6 MiB
in size. So does the Android project platform/frameworks/base.
Doing a clone of either project with JGit takes forever to checkout
the files into the working directory, because delta decompression
tends to be very expensive as we need to constantly reposition the
base stream for each copy instruction. This can be made worse by
a very bad ordering of offsets, possibly due to an XML editor that
doesn't preserve the order of elements in the file very well.
Increasing the threshold to the same limit PackWriter uses when
doing delta compression (50 MiB) permits a default configured
JGit to decompress these XML file objects using the faster
random-access arrays, rather than re-seeking through an inflate
stream, significantly reducing checkout time after a clone.
Since this new limit may be dangerously close to the JVM maximum
heap size, every allocation attempt is now wrapped in a try/catch
so that JGit can degrade by switching to the large object stream
mode when the allocation is refused. It will run slower, but the
operation will still complete.
The large stream mode will run very well for big objects that aren't
delta compressed, and is acceptable for delta compressed objects that
are using only forward referencing copy instructions. Copies using
prior offsets are still going to be horrible, and there is nothing
we can do about it except increase core.streamFileThreshold.
We might in the future want to consider changing the way the delta
generators work in JGit and native C Git to avoid prior offsets once
an object reaches a certain size, even if that causes the delta
instruction stream to be slightly larger. Unfortunately native
C Git won't want to do that until its also able to stream objects
rather than malloc them as contiguous blocks.
Change-Id: Ief7a3896afce15073e80d3691bed90c6a3897307
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
HistogramDiff is an alternative implementation of patience diff,
performing a search over all matching locations and picking the
longest common subsequence that has the lowest occurrence count.
If there are unique common elements, its behavior is identical to
that of patience diff.
Actual performance on real-world source files usually beats
MyersDiff, sometimes by a factor of 3, especially for complex
comparators that ignore whitespace.
Change-Id: I1806cd708087e36d144fb824a0e5ab7cdd579d73
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Adds API for performing git fetch operations.
Change-Id: Idd95664fd4e3bca03211e4ffda3e354849f92a35
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
The core.autocrlf variable can take on three values: false, true,
and input. Parsing it as a boolean is wrong, we instead need to
parse a tri-state enumeration.
Add support for parsing and setting enum values from Java from and
to the text based configuration file, and use that to handle the
autocrlf variable.
Bug: 301775
Change-Id: I81b9e33087a33d2ef2eac89ba93b9e83b7ecc223
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
ReceivePack: Rethrow exceptions caught during indexing
If we get an exception while indexing the incoming pack, its likely
a stream corruption. We already report an error to the client, but
we eat the stack trace, which makes debugging issues related to a
bug inside of JGit nearly impossible. Rethrow it under a new type
UnpackException, so embedding servers or applications can catch the
error and provide it to a human who might be able to forward such
traces onto a JGit developer for evaluation.
Change-Id: Icad41148bbc0c76f284c7033a195a6b51911beab
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Extended flags are processed and available via DirCacheEntry's
new isSkipWorkTree() and isIntentToAdd() methods. "resolve-undo"
information is completely ignored since its an optional extension.
Change-Id: Ie6e9c6784c9f265ca3c013c6dc0e6bd29d3b7233
Use 3 different types of LargeObjectException for the 3 major ways
that we can fail to load an object. For each of these use a unique
string translation which describes the root cause better than just
the ObjectId.name() does.
Change-Id: I810c98d5691b74af9fc6cbd46fc9879e35a7bdca
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Undo translation of protocol string 'unpack error'
This string is part of the network protocol, and isn't meant to
be translated into another language. Clients actually scan for
the string "unpack error " off the wire and react magically to
this information. If it were translated, they would instead have
a protocol exception, which isn't very useful when there is already
an error occurring.
Change-Id: Ia5dc8d36ba65ad2552f683bb637e80b77a7d92f0
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
A tag command is added to the Git porcelain API. Tests were
also added to stress test the tag command.
Change-Id: Iab282a918eb51b0e9c55f628a3396ff01c9eb9eb
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Implementation of a checkout (or 'git read-tree') operation which
works together with DirCache. This implementation does similar things
as WorkDirCheckout which main problem is that it works with deprecated
GitIndex. Since GitIndex doesn't support multiple stages of a file
which is required in merge situations this new implementation is
required to enable merge support.
Change-Id: I13f0f23ad60d98e5168118a7e7e7308e066ecf9c
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
If we are given a DiffEntry header that already has abbreviated
ObjectIds on it, we may still be able to resolve those locally and
output the difference. Try to do that through the new resolve API
on ObjectReader.
Change-Id: I0766aa5444b7b8fff73620290f8c9f54adc0be96
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Applications should favor the long style interface, especially when
their source input is a long type, e.g. coming from java.io.File.
This way when the index format is later changed to support a
larger file size than 2 GiB we can handle it by just changing the
entry code, and not need to fix a lot of applications.
Change-Id: I332563caeb110014e2d544dc33050ce67ae9e897
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
ObjectReader implementations may wish to use multiple threads in
order to evaluate object reuse faster. Let the reader make that
decision by passing the iteration down into the reader.
Because the work is pushed into the reader, it may need to locate a
given ObjectToPack given its ObjectId. This can easily occur if the
reader has sent a list of ObjectIds to the object database and gets
back information keyed only by ObjectId, without the ObjectToPack
handle. Expose lookup using the PackWriter's own internal map,
so the reader doesn't need to build a redundant copy to track the
assocation of ObjectId back to ObjectToPack.
Change-Id: I0c536405a55034881fb5db92a2d2a99534faed34
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
The Tag class now only supports the creation of an annotated tag
object. To read an annotated tag, applictions should use RevTag.
This permits us to have exactly one implementation, and RevTag's
is faster and more bug-free.
Change-Id: Ib573f7e15f36855112815269385c21dea532e2cf
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
The MergeResult class is enhanced to report more data about a
three-way merge. Information about conflicts and the base, ours,
theirs commits can be retrived.
Change-Id: Iaaf41a1f4002b8fe3ddfa62dc73c787f363460c2
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>
Meaningful error message when trying to check-out submodules
Currently, a NullPointerException occurs in this case. We should
instead throw a more meaningful Exception with a proper message.
This is a very "stupid" implementation which simply checks for
the existence of a ".gitmodules" file.
Bug: 300731
Bug: 306765
Bug: 308452
Bug: 314853
Change-Id: I155aa340a85cbc5d7d60da31dba199fc30689b67
Signed-off-by: Mathias Kinzler <mathias.kinzler@sap.com>
File pairs that are very dissimilar during a diff were not being
broken apart into their constituent ADD/DELETE pairs. The leads to
sub-optimal rename detection. Take, for example, this situation:
A file exists at src/a.txt containing "foo". A user renames src/a.txt
to src/b.txt, then adds a new src/a.txt containing "bar".
Even though the old a.txt and the new b.txt are identical, the
rename detection algorithm would not detect it as a rename since
it was already paired in a MODIFY. I added code to split all
MODIFYs below a certain score into their constituent ADD/DELETE
pairs. This allows situations like the one I described above to be
more correctly handled.
Change-Id: I22c04b70581f206bbc68c4cd1ee87a1f663b418e
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
A programming error using the Inflater API led to an infinite
loop within IndexPack, caused by the Inflater returning 0 from
the inflate() method, but it didn't want more input. This happens
when it has reached the end of the stream, or has reached a spot
asking for an external dictionary. Such a case is a failure for us,
and we should abort out.
Thanks to Alex for pointing out that we had 3 implementations of
the inflate rountine, which should be consolidated into one and
use a switch to determine where to load data from.
Bug: 317416
Change-Id: I34120482375b687ea36ed9154002d77047e94b1f
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
The new Add command adds files to the Git Index.
It uses the DirCache to access the git index. It
works also in case of an existing conflict.
Fileglobs (e.g. *.c) are not yet supported.
The new Add command does add ignored files because
there is no gitignore support in jgit yet.
Bug: 318440
Change-Id: If16fdd4443e46b27361c2a18ed8f51668af5d9ff
Signed-off-by: Stefan Lay <stefan.lay@sap.com>
Similar to what we did with diff, implement whitespace ignore options
for log too. This requires us to define some means of creating any
RawText object type at will inside of DiffFormatter, so we define a
new factory interface to construct RawText instances on demand.
Unfortunately we have to copy the entire block of common options.
args4j only processes the options/arguments on the one command class
and Java doesn't support multiple inheritance.
Change-Id: Ia16cd3a11b850fffae9fbe7b721d7e43f1d0e8a5
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Passing around the OutputStream and the Repository is crazy. Instead
put the stream in the constructor, since this formatter exists only to
output to the stream, and put the repository as a member variable that
can be optionally set.
Change-Id: I2bad012fee7f40dc1346700ebd19f1e048982878
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Content similarity based rename detection is performed only after
a linear time detection is performed using exact content match on
the ObjectIds. Any names which were paired up during that exact
match phase are excluded from the inexact similarity based rename,
which reduces the space that must be considered.
During rename detection two entries cannot be marked as a rename
if they are different types of files. This prevents a symlink from
being renamed to a regular file, even if their blob content appears
to be similar, or is identical.
Efficiently comparing two files is performed by building up two
hash indexes and hashing lines or short blocks from each file,
counting the number of bytes that each line or block represents.
Instead of using a standard java.util.HashMap, we use a custom
open hashing scheme similiar to what we use in ObjecIdSubclassMap.
This permits us to have a very light-weight hash, with very little
memory overhead per cell stored.
As we only need two ints per record in the map (line/block key and
number of bytes), we collapse them into a single long inside of
a long array, making very efficient use of available memory when
we create the index table. We only need object headers for the
index structure itself, and the index table, but not per-cell.
This offers a massive space savings over using java.util.HashMap.
The score calculation is done by approximating how many bytes are
the same between the two inputs (which for a delta would be how much
is copied from the base into the result). The score is derived by
dividing the approximate number of bytes in common into the length
of the larger of the two input files.
Right now the SimilarityIndex table should average about 1/2 full,
which means we waste about 50% of our memory on empty entries
after we are done indexing a file and sort the table's contents.
If memory becomes an issue we could discard the table and copy all
records over to a new array that is properly sized.
Building the index requires O(M + N log N) time, where M is the
size of the input file in bytes, and N is the number of unique
lines/blocks in the file. The N log N time constraint comes
from the sort of the index table that is necessary to perform
linear time matching against another SimilarityIndex created for
a different file.
To actually perform the rename detection, a SxD matrix is created,
placing the sources (aka deletions) along one dimension and the
destinations (aka additions) along the other. A simple O(S x D)
loop examines every cell in this matrix.
A SimilarityIndex is built along the row and reused for each
column compare along that row, avoiding the costly index rebuild
at the row level. A future improvement would be to load a smaller
square matrix into SimilarityIndexes and process everything in that
sub-matrix before discarding the column dimension and moving down
to the next sub-matrix block along that same grid of rows.
An optional ProgressMonitor is permitted to be passed in, allowing
applications to see the progress of the detector as it works through
the matrix cells. This provides some indication of current status
for very long running renames.
The default line/block hash function used by the SimilarityIndex
may not be optimal, and may produce too many collisions. It is
borrowed from RawText's hash, which is used to quickly skip out of
a longer equality test if two lines have different hash functions.
We may need to refine this hash in the future, in order to minimize
the number of collisions we get on common source files.
Based on a handful of test commits in JGit (especially my own
recent rename repository refactoring series), this rename detector
produces output that is very close to C Git. The content similarity
scores are sometimes off by 1%, which is most probably caused by
our SimilarityIndex type using a different hash function than C
Git uses when it computes the delta size between any two objects
in the rename matrix.
Bug: 318504
Change-Id: I11dff969e8a2e4cf252636d857d2113053bdd9dc
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
amend commit: Refactor repository construction to builder class
During code review, Alex raised a few comments about commit
532421d989 ("Refactor repository construction to builder class").
Due to the size of the related series we aren't going to go back
and rebase in something this minor, so resolve them as a follow-up
commit instead.
Change-Id: Ied52f7a8f7252743353c58d20bfc3ec498933e00
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
JGit does not currently do rename detection during diffs. I added
a class that, given a TreeWalk to iterate over, can output a list
of DiffEntry's for that TreeWalk, taking into account renames. This
class only detects renames by SHA1's. More complex rename detection,
along the lines of what C Git does will be added later.
Change-Id: I93606ce15da70df6660651ec322ea50718dd7c04
We no longer need an ObjectLoader to be lazy and try to delay
the materialization of the object content. That was done only
to support PackWriter searching for a good reuse candidate.
Instead, simplify the code base by doing the materialization
immediately when the loader asks for it, because any caller
asking for the loader is going to need the content.
Change-Id: Id867b1004529744f234ab8f9cfab3d2c52ca3bd0
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Shawn O. Pearce
Mathias Kinzler
Christian Halstrick
Matthias Sohn
Sasa Zivkov
Robin Rosenberg
Chris Aniszczyk
Marc Strapetz
Jeff Schumacher
Stefan Lay