This is the format given by the Eclipse legal doc generator [1].

[1] https://www.eclipse.org/projects/tools/documentation.php?id=technology.jgit

Bug: 548298
Change-Id: I8d8cabc998ba1b083e3f0906a8d558d391ffb6c4
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This should help to detect if measured fsTimeResolution is too small.

Change-Id: Id1f54dbdedb52b17859904e47776fa3a5887b8be
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This enables higher file timestamp resolution on filesystems like ext4,
Mac APFS (1ns) or NTFS (100ns) providing high timestamp resolution on
filesystem level.

Note:
- on some OSes Java 8,9 truncate milliseconds, see
https://bugs.openjdk.java.net/browse/JDK-8177809, fixed in Java 10
- UnixFileAttributes truncates timestamp resolution to microseconds when
converting the internal representation to FileTime exposed in the API,
see https://bugs.openjdk.java.net/browse/JDK-8181493
- WindowsFileAttributes also provides only microsecond resolution

Change-Id: I25ffff31a3c6f725fc345d4ddc2f26da3b88f6f2
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Convert anonymous inner classes to lambda expressions or member
references

Bug: 545856
CQ: 19537
Change-Id: I621431c178e8b99316314602f7c66c9a36f9ae98
Signed-off-by: Carsten Hammer <carsten.hammer@t-online.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: I22a244114ef973b3801cf3b639ff782f21c02f98
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Psuedorefs like FETCH_HEAD and MERGE_HEAD are supposed to be directly
under the .git directory, not in other locations in the SEARCH_PATH
like refs/ and refs/heads/.  Use exactRef to access them.

Change-Id: Iab8ac47008822fa78fc0691e239e518c34d7a98e
Signed-off-by: Jonathan Nieder <jrn@google.com>

In DFS implementations the reference table can fall out of sync, but
it is not possible to check this situation in the current API.

Add a property to the Refs indicating the order of its updates.  This
version is set only by RefDatabase implementations that support
versioning (e.g reftable based).

Caller is responsible to check if the reference db creates versioned
refs before accessing getUpdateIndex(). E.g:

   Ref ref = refdb.exactRef(...);
   if (refdb.hasVersioning()) {
       ref.getUpdateIndex();
   }

Change-Id: I0d5ec8e8df47c730301b2e12851a6bf3dac9d120
Signed-off-by: Ivan Frade <ifrade@google.com>

Change-Id: I2d3e426a3391923f8a690ac68fcc33851f3eb419
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

If a repo frequently uses PackedBatchRefUpdates, there is likely to be
contention on the packed-refs file, so it's not appropriate to fail
immediately the first time we fail to acquire a lock. Add some logic to
RefDirectory to support general retrying of lock acquisition.

Currently, there is a hard-coded wait starting at 100ms and backing off
exponentially to 1600ms, for about 3s of total wait. This is no worse
than the hard-coded backoff that JGit does elsewhere, e.g. in
FileUtils#delete. One can imagine a scheme that uses per-repository
configuration of backoff, and the current interface would support this
without changing any callers.

Change-Id: I4764e11270d9336882483eb698f67a78a401c251

Run with @Parameterized, so we don't have to duplicate test setup for
each atomic/non-atomic test. We still have to have two different sets of
asserts for the cases where the behavior is different. In fact, this is
a readability win: it emphasizes that performing the exact same setup
except for the atomic setting will have different behavior.

Change-Id: I78a8214075e204732a423341f14c09de273a7854

The existing packed-refs file provides a mechanism for implementing
atomic multi-ref updates without any changes to the on-disk format or
lockfile protocol. We just need to make sure that there are no loose
refs involved in the transaction, which we can achieve by packing the
refs while holding locks on all loose refs. Full details of the
algorithm are in the PackedBatchRefUpdate javadoc.

This change does not implement reflog support, which will come in a
later change.

Change-Id: I09829544a0d4e8dbb141d28c748c3b96ef66fee1

ReceiveCommand.Result has a slightly richer set of possibilities, so it
makes sense for RefUpdate.Result to have more values in order to match.
In particular, this allows us to return REJECTED_MISSING_OBJECT from
RefUpdate when an object is missing.

The comment in RefUpdate#safeParse about expecting some old objects to be
missing is only applicable to the old ID, not the new ID. A missing new
ID is a bug or programmer error, and we should not update a ref to point
to one.

Fix various tests that started failing because they depended for no good
reason on setting refs to point to nonexistent objects; it's always easy
to create a real object when necessary.

It is possible that some downstream users of RefUpdate.Result might
choose to handle one of the new statuses differently, for example by
providing a more user-readable error message; that is not done in this
change.

Change-Id: I734b1c32d5404752447d9e20329471436ffe05fc

Some downstream code checks whether a ReceiveCommand is a create or a
delete based on the type field. Other downstream code (in particular a
good chunk of Gerrit code I wrote) checks the same thing by comparing
oldId/newId to zeroId. Unfortunately, there were no strict checks in the
constructor that ensures that zeroId is only set for oldId/newId if the
type argument corresponds, so a caller that passed mismatched IDs and
types would observe completely undefined behavior as a result. This is
and always has been a misuse of the API; throw IllegalArgumentException
so the caller knows that it is a misuse.

Similarly, throw from the constructor if oldId/newId are null. The
non-nullness requirement was already documented. Fix RefDirectoryTest to
not do the wrong thing.

Change-Id: Ie2d0bfed8a2d89e807a41925d548f0f0ce243ecf

Since the introduction of generic type parameter inference in Java 7,
it's not necessary to explicitly specify the type of generic parameters.

Enable the warning in Eclipse, and fix all occurrences.

Change-Id: I9158caf1beca5e4980b6240ac401f3868520aad0
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Set missingOverrideAnnotation=warning in Eclipse compiler preferences
which enables the warning:

  The method <method> of type <type> should be tagged with @Override
  since it actually overrides a superclass method

Justification for this warning is described in:

  http://stackoverflow.com/a/94411/381622

Enabling this causes in excess of 1000 warnings across the entire
code-base. They are very easy to fix automatically with Eclipse's
"Quick Fix" tool.

Fix all of them except 2 which cause compilation failure when the
project is built with mvn; add TODO comments on those for further
investigation.

Change-Id: I5772061041fd361fe93137fd8b0ad356e748a29c
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Change-Id: I7c545d06b1bced678c020fab9af1382bc4416b6e
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

The parameter name 'totalWork' was hiding a class member variable
of the same name.

Change-Id: I646525e82900e23ffabfc756bcf5052ef873656a
Signed-off-by: David Pursehouse <david.pursehouse@sonymobile.com>

getRef() loops over its search path to find a ref:

	Ref ref = null;
	for (String prefix : SEARCH_PATH) {
		ref = readRef(prefix + needle, packed);
		if (ref != null) {
			ref = resolve(ref, 0, null, null, packed);
			break;
		}
	}
	fireRefsChanged();
	return ref;

If readRef returns null (indicating that the ref does not exist), the
loop continues so we can find the ref later in the search path.  And
resolve should never return null, so if we return null it should mean
we exhausted the entire search path and didn't find the ref.

... except that resolve can return null: it does so when it has
followed too many symrefs and concluded that there is a symref loop:

	if (MAX_SYMBOLIC_REF_DEPTH <= depth)
		return null; // claim it doesn't exist

Continue the loop instead of returning null immediately.  This makes
the behavior more consistent.

Arguably getRef should throw an exception when a symref loop is
detected.  That would be a more invasive change, so if it's a good
idea it will have to wait for another patch.

Change-Id: Icb1c7fafd4f1e34c9b43538e27ab5bbc17ad9eef
Signed-off-by: Jonathan Nieder <jrn@google.com>

When asked to read a symref pointing to a branch-yet-to-be-born (such
as HEAD in a newly initialized repository), DfsRepository and
FileRepository return different results.

FileRepository:

	exactRef("HEAD") => null

DfsRepository:

	exactRef("HEAD") => SymbolicRef[HEAD -> refs/heads/master=00000000]

getRef("HEAD") returns the same as DfsRepository's exactRef in both
backends.

The intended behavior is the DfsRepository one: exactRef() is supposed
to be like getRef(), but more exact because it doesn't need to
traverse the search path.

The discrepancy is because DfsRefDatabase implements exactRef()
directly with the intended semantics, while RefDirectory uses a
fallback implementation built on top of getRefs().  getRefs() skips
symrefs to an unborn branch.

Override the fallback implementation with a correct implementation
that is similar to getRef() to avoid this.  A followup change will fix
the fallback.

Change-Id: Ic138a5564a099ebf32248d86b93e2de9ab3c94ee
Reported-by: David Pursehouse <david.pursehouse@sonymobile.com>
Improved-by: Christian Halstrick <christian.halstrick@sap.com>
Bug: 478865

exactRef(ref1, ref2, ref3) requests multiple specific refs in a single
lookup, which may be faster in some backends than looking them up one by
one.

firstExactRef generalizes getRef by finding the first existing ref from
the list of refs named.  Its main purpose is for the default
implementation of getRef (finding the first existing ref in a search
path).  Hopefully it can be useful for other operations that look for
refs in a search path (e.g., git log --notes=<name>), too.

Change-Id: I5c6fcf1d3920f6968b8b97f3d4c3a267258c4b86
Signed-off-by: Jonathan Nieder <jrn@google.com>

Unlike getRef(name), the new exactRef method does not walk the search
path.  This should produce a less confusing result than getRef when the
exact ref name is known: it will not try to resolve refs/foo/bar to
refs/heads/refs/foo/bar even when refs/foo/bar does not exist.

It can be faster than both getRefs(ALL).get(name) and getRef(name)
because it only needs to examine a single ref.

A follow-up change will introduce a findRef synonym to getRef and
deprecate getRef to make the choice a caller is making more obvious
(exactRef or findRef, with the same semantics as getRefs(ALL).get and
getRefs(ALL).findRef).

Change-Id: If1bd09bcfc9919e7976a4d77f13184ea58dcda52
Signed-off-by: Jonathan Nieder <jrn@google.com>

When the caller specifies to JGit in advance that a ref-update is a
non-fast-forward update, and that those are permitted, we should never
need to call the potentially expensive isMergedInto() check. Re-checking
that the older commit is /not/ reachable from the newer is superfluous.

http://dev.eclipse.org/mhonarc/lists/jgit-dev/msg02258.html

Change-Id: I4bbf593de4dcea6b6f082881c1a33cb3a6a7fb89
Signed-off-by: Roberto Tyley <roberto.tyley@gmail.com>

Formerly the 4-arg constructor did not do this, which was unfortunate
as that constructor's the only way for an external user of JGit to set
the /type/ of the ref-update - which you might want to do to indicate
that the update is expected to be a UPDATE_NONFASTFORWARD, and thus does
not require expensive isMergedInto() calculations:

http://dev.eclipse.org/mhonarc/lists/jgit-dev/msg02258.html

Change-Id: I84c5e4927131e105bed93e31a62da6367c78de32
Signed-off-by: Roberto Tyley <roberto.tyley@gmail.com>

I was seeing output like this while running The BFG:

Updating references:    200% (374/187)

...issue sneaked in with 5cf53fda I think.

The update call is also moved to the end of the loop, as update() is
only supposed to be called after work has been done ("Denote that some
work units have been completed").

Change-Id: I1620fa75be16dc80df44745d0e123ea512762e31
Signed-off-by: Robin Stocker <robin@nibor.org>

Instead of re-reading all refs after each update, execute
the deletes first, then read all refs once and perform
the check for conflicting ref names in memory.

Change-Id: I17d0b3ccc27f868c8497607d8e57bf7082e65ba3

This breaks all existing callers once. Applications are not supposed
to build against the internal storage API unless they can accept API
churn and make necessary updates as versions change.

Change-Id: I2ab1327c202ef2003565e1b0770a583970e432e9

JGit was not able to lookup refs which had the name of files which exist
in the .git folder. When JGit was looking up a ref named X it has a
fixed set of directories where it searched for files named X
(ignore packed refs for now). First directory to search for is .git. In
case of the ref named 'config' it searched there for this file, found it
(it's the .git/config file with the repo configuration in it), parsed
it, found it is an invalid ref and stopped searching. It never looked
for a file .git/refs/heads/config.

I changed JGit in a way that when it finds a file in GIT_DIR which
corresponds to a ref name and if this file doesn't contain a valid ref
then it will ignore the InvalidObjectIdException and continue searching.

Change-Id: Ic26a329fb1624a5b2b2494c78bac4bd76817c100
Bug: 381574
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Stefan Lay <stefan.lay@sap.com>

Implements a garbage collector for FileRepositories. Main ideas are
copied from the garbage collector for DFS based repos
(DfsGarbageCollector). Added functionalities are
- pruning loose objects
- handling of the index
- packing refs
- handling of reflogs (objects referenced from reflog will not be
pruned/)

These are features of a GC which are not handled in this change and
which should come with subsequent changes:
- unpacking packed objects into loose objects (to support that pruning
packed objects doesn't delete them until they are older than two weeks)
- expiration of reflogs
- support for configuration parameters (e.g. gc.pruneExpire)

Change-Id: I14ea5cb7e0fd1b5c50b994fd77f4e05bfbb9d911
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>

Previously if a packed-refs file was racily clean then there
was a 2.5 second window in which each call to getPackedRefs
would increment the mod count causing a RefsChangedEvent to be
fired since the FileSnapshot would report the file as modified.

If a RefsChangedListener called getRef/getRefs from the
onRefsChanged method then a StackOverflowError could occur
since the stack could be exhausted before the 2.5 second
window expired and the packed-refs file would no longer
report being modified.

Now a SHA-1 is computed of the packed-refs file and the
mod count is only incremented when the packed refs are
successfully set and the id of the new packed-refs file
does not match the id of the old packed-refs file.

Change-Id: I8cab6e5929479ed748812b8598c7628370e79697

A set of ref names like ('a/b' and 'a+b') would cause the RefDirectory
to think that the set of refs have changed because it traversed the
'a' directory in the subtree before looking at 'a+b', but it then
compared with the know refs which are sorted with 'a+b' first.

Fix this by traversing the refs tree in another order. Treat a directory
as if they ends with a '/' before deciding on the order to traverse
the refs tree.

Bug: 348834
Change-Id: I23377f8df00c7252bf27dbcfba5da193c5403917
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>

Since this change may affect performance and memory consumption on every
access to a loose ref I explicitly made it a RFC to collect opinions.

Previously RefDirectory.scanRef() was not detecting an update of a
loose ref when the update didn't changed the modification time of
the backing file. RefDirectory cached loose refs and the way to detect
outdated cache entries was to compare lastmodification timestamp on the
file representing the ref. If two updates to the same ref happen faster
than the filesystem-timer granularity (for linux this is 2 seconds)
there is the possiblity that we don't detect the update.

Because of this bug EGit's PushOperationTest only works with 2 second
sleeps inside.

This change let RefDirectory use FileSnapshot to detect such situations.
FileSnapshot helps to remember when a file was last read from disk and
therefore enables to decide when to load a file from disk although
modification time has not changed.

Change-Id: I03b9a137af097ec69c4c5e2eaa512d2bdd7fe080
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>

RefDirectory did not correctly follow the contract of RefList.  The
contract says if you use add() method of RefList builder, you MUST
sort() it afterwards, and later every other method assumes that list
is properly sorted (especially the binary search in the find() and
get() methods).  Instead RefDirectory class tried to scan the refs
recursively while sorting every folder in the process before
processing and did not call sort().

For example, when scanning the contents of refs/tags project1 string
is smaller than project1-*, so it will recursively go into the folder
and add these tags first and only then will add project-* ones. This
will result in a broken list (any project1-* string is less than
project1/* one, but they all appear after them in the list), that's
why binary search will fail making loose RefList and the whole local
RefMap completely unusable.

Change-Id: Ibad90017e3b2435b1396b69a22520db4b1b022bb
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Instead of tracking the length and modification time by hand, rely
on FileSnapshot to tell RefDirectory when the $GIT_DIR/packed-refs
file has been changed or should be re-read from disk.

Change-Id: I067d268dfdca1d39c72dfa536b34e6a239117cc3
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Eclipse has some problem re-running single JUnit tests if
the tests are in Junit 3 format, but the JUnit 4 launcher
is used. This was quite unnecessary and the move was not
completed. We still have no JUnit4 test.

This completes the extermination of JUnit3. Most of the
work was global searce/replace using regular expression,
followed by numerous invocarions of quick-fix and organize
imports and verification that we had the same number of
tests before and after.

- Annotations were introduced.
- All references to JUnit3 classes removed
- Half-good replacement for getting the test name. This was
  needed to make the TestRngs work. The initialization of
  TestRngs was also made lazily since we can not longer find
  out the test name in runtime in the @Before methods.
- Renamed test classes to end with Test, with the exception
  of TestTranslateBundle, which fails from Maven
- Moved JGitTestUtil to the junit support bundle

Change-Id: Iddcd3da6ca927a7be773a9c63ebf8bb2147e2d13
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

This move isolates all of the local file specific implementation code
into a single package, where their package-private methods and support
classes are properly hidden away from the rest of the core library.

Because of the sheer number of files impacted, I have limited this
change to only the renames and the updated imports.

Change-Id: Icca4884e1a418f83f8b617d0c4c78b73d8a4bd17
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

This commit actually does three major changes to the way references
are handled within JGit.  Unfortunately they were easier to do as
a single massive commit than to break them up into smaller units.

Disambiguate symbolic references:
---------------------------------

  Reporting a symbolic reference such as HEAD as though it were
  any other normal reference like refs/heads/master causes subtle
  programming errors.  We have been bitten by this error on several
  occasions, as have some downstream applications written by myself.

  Instead of reporting HEAD as a reference whose name differs from
  its "original name", report it as an actual SymbolicRef object
  that the application can test the type and examine the target of.

  With this change, Ref is now an abstract type with different
  subclasses for the different types.

  In the classical example of "HEAD" being a symbolic reference to
  branch "refs/heads/master", the Repository.getAllRefs() method
  will now return:

      Map<String, Ref> all = repository.getAllRefs();
      SymbolicRef HEAD = (SymbolicRef) all.get("HEAD");
      ObjectIdRef master = (ObjectIdRef) all.get("refs/heads/master");

      assertSame(master,               HEAD.getTarget());
      assertSame(master.getObjectId(), HEAD.getObjectId());

      assertEquals("HEAD",              HEAD.getName());
      assertEquals("refs/heads/master", master.getName());

  A nice side-effect of this change is the storage type of the
  symbolic reference is no longer ambiguous with the storge type
  of the underlying reference it targets.  In the above example,
  if master was only available in the packed-refs file, then the
  following is also true:

      assertSame(Ref.Storage.LOOSE,  HEAD.getStorage());
      assertSame(Ref.Storage.PACKED, master.getStorage());

  (Prior to this change we returned the ambiguous storage of
   LOOSE_PACKED for HEAD, which was confusing since it wasn't
   actually true on disk).

  Another nice side-effect of this change is all intermediate
  symbolic references are preserved, and are therefore visible
  to the application when they walk the target chain.  We can
  now correctly inspect chains of symbolic references.

  As a result of this change the Ref.getOrigName() method has been
  removed from the API.  Applications should identify a symbolic
  reference by testing for isSymbolic() and not by using an arcane
  string comparsion between properties.

Abstract the RefDatabase storage:
---------------------------------

  RefDatabase is now abstract, similar to ObjectDatabase, and a
  new concrete implementation called RefDirectory is used for the
  traditional on-disk storage layout.  In the future we plan to
  support additional implementations, such as a pure in-memory
  RefDatabase for unit testing purposes.

Optimize RefDirectory:
----------------------

  The implementation of the in-memory reference cache, reading, and
  update routines has been completely rewritten.  Much of the code
  was heavily borrowed or cribbed from the prior implementation,
  so copyright notices have been left intact as much as possible.

  The RefDirectory cache no longer confuses symbolic references
  with normal references.  This permits the cache to resolve the
  value of a symbolic reference as late as possible, ensuring it
  is always current, without needing to maintain reverse pointers.

  The cache is now 2 sorted RefLists, rather than 3 HashMaps.
  Using sorted lists allows the implementation to reduce the
  in-memory footprint when storing many refs.  Using specialized
  types for the elements allows the code to avoid additional map
  lookups for auxiliary stat information.

  To improve scan time during getRefs(), the lists are returned via
  a copy-on-write contract.  Most callers of getRefs() do not modify
  the returned collections, so the copy-on-write semantics improves
  access on repositories with a large number of packed references.

  Iterator traversals of the returned Map<String,Ref> are performed
  using a simple merge-join of the two cache lists, ensuring we can
  perform the entire traversal in linear time as a function of the
  number of references: O(PackedRefs + LooseRefs).

  Scans of the loose reference space to update the cache run in
  O(LooseRefs log LooseRefs) time, as the directory contents
  are sorted before being merged against the in-memory cache.
  Since the majority of stable references are kept packed, there
  typically are only a handful of reference names to be sorted,
  so the sorting cost should not be very high.

  Locking is reduced during getRefs() by taking advantage of the
  copy-on-write semantics of the improved cache data structure.
  This permits concurrent readers to pull back references without
  blocking each other.  If there is contention updating the cache
  during a scan, one or more updates are simply skipped and will
  get picked up again in a future scan.

  Writing to the $GIT_DIR/packed-refs during reference delete is
  now fully atomic.  The file is locked, reparsed fresh, and written
  back out if a change is necessary.  This avoids all race conditions
  with concurrent external updates of the packed-refs file.

  The RefLogWriter class has been fully folded into RefDirectory
  and is therefore deleted.  Maintaining the reference's log is
  the responsiblity of the database implementation, and not all
  implementations will use java.io for access.

  Future work still remains to be done to abstract the ReflogReader
  class away from local disk IO.

Change-Id: I26b9287c45a4b2d2be35ba2849daa316f5eec85d
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>