PackedBatchRefUpdate was creating a new packed-refs list that was
potentially unsorted. This would be papered over when the list was
read back from disk in parsePackedRef, which detects unsorted ref
lists on reading, and sorts them. However, the BatchRefUpdate also
installed the new (unsorted) list in-memory in
RefDirectory#packedRefs.

With the timestamp granularity code committed to stable-5.1, we can
more often accurately decide that the packed-refs file is clean, and
will return the erroneous unsorted data more often. Unluckily timed
delays also cause the file to be clean, hence this problem was
exacerbated under load.

The symptom is that refs added by a BatchRefUpdate would stop being
visible directly after they were added. In particular, the Gerrit
integration tests uses BatchRefUpdate in its setup for creating the
Admin group, and then tries to read it out directly afterward.

The tests recreates one failure case. A better approach would be to
revise RefList.Builder, so it detects out-of-order lists and
automatically sorts them.

Fixes https://bugs.eclipse.org/bugs/show_bug.cgi?id=548716 and
https://bugs.chromium.org/p/gerrit/issues/detail?id=11373.

Bug: 548716
Change-Id: I613c8059964513ce2370543620725b540b3cb6d1
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

These warnings were missed to address in a0048208 which introduced them.

Change-Id: Ia2d15fdce72c10378d020682b80fe7fc548c0d4c
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

It's expected that jgit should work without native git installation.
In such case Security Manager can be configured to deny access to the
files outside of git repository. JGit tries to find cygwin
installation. If Security manager restricts access to some folders
in PATH, it should be considered that those folders are absent
for jgit.
Also JGit tries to detect if symbolic links are supported by OS. If
security manager forbids creation of symlinks, it should be assumed
that symlinks aren't supported.

Bug: 550115
Change-Id: Ic4b243cada604bc1090db6cc1cfd74f0fa324b98
Signed-off-by: Nail Samatov <sanail@yandex.ru>

Teach UploadPack to take a provider of URIs corresponding to cached
packs. When fetching, if the client supports the packfile-uri feature,
and if such a cached pack were to be streamed, instead send the
corresponding URI.

This packfile-uri feature is implemented in the jt/fetch-cdn-offload
branch of Git. There is interest in this feature [1], but it is not yet
merged.

[1] https://public-inbox.org/git/cover.1552073690.git.jonathantanmy@google.com/

Change-Id: I9a32dae131c9c56ad2ff4a8a9638ae3b5e44dc15
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>

Also use MessageFormat as done elsewhere.

Change-Id: I36a4df9002310fa28321de9d325ee213f3cbd433
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This fixes timezone reads out of the reflog.

Change-Id: I126d8742e5e904a074c544514180720466164f7c
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>

Previously, the API did not enforce ordering of writes.  Misuse of
this API would lead to data effectively being lost.

Guard against that with IllegalArgumentException, and add a test.

Change-Id: I04f55c481d60532fc64d35fa32c47037a03988ae
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>

Change-Id: I95208f7a05919b5019895cf41ae378c97da6e680
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>

Small reftables omit the log index. Currently,
ReftableWriter#shouldHaveIndex does this if there is a single-block
log, but other writers could decide on different criteria.

In the case that the log index is missing, we have to linearly search
for the right block. It is never appropriate to use binary search on
blocks for log data, as the blocks are compressed and therefore
irregularly sized.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Change-Id: Id59874edf6bf45c7dec502d9465888e077ffe198

So far the git configuration and the system wide git configuration were
always reloaded when jgit accessed these global configuration files to
access global configuration options which are not in the context of a
single git repository. Cache these configurations in SystemReader and
only reload them if their file metadata observed using FileSnapshot
indicates a modification.

Change-Id: I092fe11a5d95f1c5799273cacfc7a415d0b7786c
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

- fix handling of interrupts in FileStoreAttributes#saveToConfig
- increase retry wait time to 100ms
- don't wait after last retry
- dont retry if failure is caused by another exception than
LockFailedException

Change-Id: I108c012717d2bcce71f2c6cb9cf0879de704ebc2
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: I4de75d12ec9e61193494916307289378cdb6220e
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Move the implementation of the static equals() method to a new method
and suppress the error. Deprecate the old method to signal that we
intend to remove it in the next major release.

See https://errorprone.info/bugpattern/AmbiguousMethodReference

Change-Id: I5e29c97f4db3e11770be589a6ccd785e2c9ac7f2
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Error Prone reports:

  [NarrowingCompoundAssignment] Compound assignments from long to int
  hide lossy casts

and

  [NarrowingCompoundAssignment] Compound assignments from int to byte
  hide lossy casts

  See https://errorprone.info/bugpattern/NarrowingCompoundAssignment

Fix the warnings by adding explicit casts or changing types as
necessary.

Now that all occurrences of the warning are fixed, increase its
severity to ERROR.

Change-Id: Idb3670e6047b146ae37daee07212ff9455512623
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Increase the safety factor to 2.5x for extra safety if max of measured
timestamp resolution and measured minimal racy threshold is < 100ms, use
1.25 otherwise since for large filesystem resolution values the
influence of finite resolution of the system clock should be negligible.

Before, not yet using the newly introduced minRacyThreshold measurement,
the threshold was 1.1x FS resolution, and we could issue the
following sequence of events,

  start
  create-file
  read-file (currentTime)
  end

which had the following timestamps:

  create-file 1564589081
  start 1564589082
  read 1564589082
  end 1564589082

In this case, the difference between create-file and read is 5ms,
which exceeded the 4ms FS resolution, even though the events together
took just 2ms of runtime.

Reproduce with:
  bazel test --runs_per_test=100 \
    //org.eclipse.jgit.test:org_eclipse_jgit_internal_storage_file_FileSnapshotTest

The file system timestamp resolution is 4ms in this case.

This code assumes that the kernel and the JVM use the same clock that
is synchronized with the file system clock. This seems plausible,
given the resolution of System.currentTimeMillis() and the latency for
a gettimeofday system call (typically ~1us), but it would be good to
justify this with specifications.

Also cover a source of flakiness: if the test runs under extreme load,
then we could have

  start
  create-file
  <long delay>
  read
  end

which would register as an unmodified file. Avoid this by skipping the
test if end-start is too big.

[msohn]:
- downported from master to stable-5.1
- skip test if resolution is below 10ms
- adjust safety factor to 1.25 for resolutions above 100ms

Change-Id: I87d2cf035e01c44b7ba8364c410a860aa8e312ef
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Since we now measure file time resolution we can use it to replace the
hard coded wait time of 25ms. FileSnapshot#equals will return true until
the mtime of the old (o) and the new FileSnapshot (n) differ by at least
one  file time resolution.

Change-Id: Icb713a80ce9eb929242ed083406bfb6650c72223
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Cache FileStoreAttributeCache entries since looking up FileStore for a
file may be expensive on some platforms.

Implement a simple LRU cache based on ConcurrentHashMap using a simple
long counter to order access to cache entries.

Change-Id: I4881fa938ad2f17712c05da857838073a2fc4ddb
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Signed-off-by: Marc Strapetz <marc.strapetz@syntevo.com>
Also-By: Marc Strapetz <marc.strapetz@syntevo.com>

Use the fallback timestamp resolution as already described in the
javadoc of these methods. Using zero file timestamp resolution doesn't
make sense.

Change-Id: Iaad2a0f99c3be3678e94980a0a368181b6aed38c
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

To enable persisting the minimal racy threshold per FileStore add a
new config option to the user global git configuration:

- Config section is "filesystem"
- Config subsection is concatenation of
  - Java vendor (system property "java.vendor")
  - Java version (system property "java.version")
  - FileStore's name, on Windows we use the attribute volume:vsn instead
    since  the name is not necessarily unique.
  - separated by '|'
  e.g.
    "AdoptOpenJDK|1.8.0_212-b03|/dev/disk1s1"
  The same prefix is used as for filesystem timestamp resolution, so
  both values are stored in the same config section
- The config key for minmal racy threshold is "minRacyThreshold" as a
  time value, supported time units are those supported by
  DefaultTypedConfigGetter#getTimeUnit
- measure for 3 seconds to limit runtime which depends on hardware, OS
  and Java version being used

If the minimal racy threshold is configured for a given FileStore the
configured value is used instead of measuring it.

When the minimal racy threshold was measured it is persisted in the user
global git configuration.

Rename FileStoreAttributeCache to FileStoreAttributes since this class
is now declared public in order to enable exposing all attributes in one
object.

Example:

[filesystem "AdoptOpenJDK|11.0.3|/dev/disk1s1"]
	timestampResolution = 7000 nanoseconds
	minRacyThreshold = 3440 microseconds

Change-Id: I22195e488453aae8d011b0a8e3276fe3d99deaea
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Also-By: Marc Strapetz <marc.strapetz@syntevo.com>

By running FileSnapshotTest#detectFileModified we found that the sum of
measured filesystem timestamp resolution and measured clock resolution
may yield a too small interval after a file has been modified which we
need to consider racily clean. In our tests we didn't find this behavior
on all systems we tested on, e.g. on MacOS using APFS and Java 8 and 11
this effect was not observed.

On Linux (SLES 15, kernel 4.12.14-150.22-default) we collected the
following test results using Java 8 and 11:

In 23-98% of 10000 test runs (depending on filesystem type and Java
version) the test failed, which means the effective interval which needs
to be considered racily clean after a file was modified is larger than
the measured file timestamp resolution.

"delta" is the observed interval after a file has been modified but
FileSnapshot did not yet detect the modification:

"resolution" is the measured sum of file timestamp resolution and clock
resolution seen in Java.

Java version    filesystem  failures resolution  min delta   max delta
1.8.0_212-b04   btrfs	    98.6%       1 ms        3.6 ms      6.6 ms
1.8.0_212-b04   ext4        82.6%       3 ms        1.1 ms      4.1 ms
1.8.0_212-b04   xfs         23.8%       4 ms        3.7 ms      3.9 ms
1.8.0_212-b04   zfs         23.1%       3 ms        4.8 ms      5.0 ms
11.0.3+7        btrfs       98.1%       3 us        0.7 ms      4.7 ms
11.0.3+7        ext4        98.1%       6 us        0.7 ms      4.7 ms
11.0.3+7        xfs         98.5%       7 us        0.1 ms      8.0 ms
11.0.3+7        zfs         98.4%       7 us        0.7 ms      5.2 ms

Mac OS
1.8.0_212       APFS        0%          1 s
11.0.3+7        APFS        0%          6 us

The observed delta is not distributed according to a normal gaussian
distribution but rather random in the observed range between "min delta"
and "max delta".

Run this test after measuring file timestamp resolution in
FS.FileAttributeCache to auto-configure JGit since it's unclear what
mechanism is causing this effect.

In FileSnapshot#isRacyClean use the maximum of the measured timestamp
resolution and the measured "delta" as explained above to decide if a
given FileSnapshot is to be considered racily clean. Add a 30% safety
margin to ensure we are on the safe side.

Change-Id: I1c8bb59f6486f174b7bbdc63072777ddbe06694d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

These are useful to avoid typos, and also for tab completion.

Change-Id: I0f2d267e46b36bc40297c9657c447f3fd8b9f831
Signed-off-by: David Turner <dturner@twosigma.com>

Repeat the test 10000 times to get statistics if measured
fsTimestampResolution is working in practice to detect racy git
situations.

Add a class to compute statistics for this test. Log delta between
lastModified and time when FileSnapshot failed to detect modification.
This happens if the racy git limit determined by measuring filesystem
timestamp resolution and clock resolution is too small. If it would be
correct FileSnapshot would always detect modification or mark it
modified if time since modification is smaller than the racy git limit.

Change-Id: Iabe7af1a7211ca58480f8902d4fa4e366932fc77
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

We should not use configuration when creating FileSnapshot when
accessing FileBasedConfig.

Change-Id: Ic521632870f18bb004751642b9d30648dd94049a
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>

Checking lastModified is time critical hence debug trace is the only way
to analyze issues since debugging is impractical.

Also add configuration for buffering of log4j output to reduce runtime
impact when debug trace is on. Limit buffer to 1MiB and comment this
configuration out since we may not always want to use buffering.

Change-Id: Ib1a0537b67c8dc3fac994a77b42badd974ce6c97
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

To enable persisting filesystem timestamp resolution per FileStore add a
new config section to the user global git configuration:

- Config section is "filesystem"
- Config subsection is concatenation of
  - Java vendor (system property "java.vm.vendor")
  - runtime version (system property "java.vm.version")
  - FileStore's name
  - separated by '|'
  e.g.
    "AdoptOpenJDK|1.8.0_212-b03|/dev/disk1s1"
  The prefix is needed since some Java versions do not expose the full
  timestamp resolution of the underlying filesystem. This may also
  depend on the underlying operating system hence concrete key values
  may not be portable.
- Config key for timestamp resolution is "timestampResolution" as a time
  value, supported time units are those supported by
  DefaultTypedConfigGetter#getTimeUnit

If timestamp resolution is already configured for a given FileStore
the configured value is used instead of measuring the resolution.

When timestamp resolution was measured it is persisted in the user
global git configuration.

Example:

[filesystem "AdoptOpenJDK|1.8.0_212-b03|/dev/disk1s1"]
	timestampResolution = 1 seconds

If locking the git config file fails retry saving the resolution up to 5
times in order to workaround races with another thread.

In order to avoid stack overflow use the fallback filesystem timestamp
resolution when loading FileBasedConfig which creates itself a
FileSnapshot to help checking if the config changed.

Note:
- on some OSes Java 8,9 truncate to milliseconds or seconds, see
https://bugs.openjdk.java.net/browse/JDK-8177809, fixed in Java 10
- UnixFileAttributes up to Java 12 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 up to
Java 12

Hence do not attempt to manually configure a higher timestamp resolution
than supported by the Java version being used at runtime.

Bug: 546891
Bug: 548188
Change-Id: Iff91b8f9e6e5e2295e1463f87c8e95edf4abbcf8
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Add a unittest.

In commit I5485db55 ("Fix FileSnapshot's consideration of file size"),
the special casing of UNKNOWN_SIZE was forgotten.

This change, together with I493f3b57b ("Measure file timestamp
resolution used in FileSnapshot") introduced a regression that would
occasionally surface in Gerrit integration tests marked UseLocalDisk,
with the symptom that creating the Admin user in NoteDb failed with a
LOCK_FAILURE.

Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Change-Id: I7ffd972581f815c144f810481103c7985af5feb0

It was reported that measuring file timestamp resolution may hang
indefinitely on nfs. Hence timeout this measurement at the known worst
filesystem timestamp resolution (FAT) of 2 seconds.

Bug: 548188
Change-Id: I17004b0aa49d5b0e76360a008af3adb911b289c0
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

RevWalk does not currently provide a --first-parent equivalent and the
feature has been requested.

Add a field to the RevWalk class to specify whether walks should
traverse first parents only. Modify Generator implementations to support
the feature.

Change-Id: I4a9a0d5767f82141dcf6d08659d7cb77c585fae4
Signed-off-by: Dave Borowitz <dborowitz@google.com>
Signed-off-by: Alex Spradlin <alexaspradlin@google.com>

As reported by Error Prone:

An inner class should be static unless it references members of its
enclosing class. An inner class that is made non-static unnecessarily
uses more memory and does not make the intent of the class clear.

See https://errorprone.info/bugpattern/ClassCanBeStatic

Change-Id: Ib99d120532630dba63cf400cc1c61c318286fc41
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
(cherry picked from commit ee40efcea4)

Error Prone reports the warning on several classes:

   [NonOverridingEquals] equals method doesn't override Object.equals;
   if this is a type-specific helper for a method that does override
   Object.equals, either inline it into the callers or rename it to
   avoid ambiguity.

   See https://errorprone.info/bugpattern/NonOverridingEquals

Most of these are in the public API, so we can't rename or inline them
without breaking the API. FileSnapshot is not part of the public API,
but clients may be using it anyway, so we also shouldn't change that.

Suppress all the warnings instead. Having the check at severity ERROR
will at least make sure we don't introduce any new occurrences.

Change-Id: I92345c11256f06b4fa03ccc13337f72af5a43591
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Reference comparison with EMPTY and MISSING_FILE is intended; these
are static instances used as markers, and will always be the same
instances.

Change-Id: Ic27f5b797bdb9370cf8f6b3b7bb3f1523d4a454c
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Issues reported by downstream analyzers.

The "hash" method can be static.

It is a good practice to group overloaded methods. Move the write(URL)
method with the other writes.

Change-Id: Ia42c0d7081333edcb77e58d5e627929d29672490
Signed-off-by: Ivan Frade <ifrade@google.com>

Downstream analyzers reported empty fields in the javadoc. I corrected
few more details:

* Fill empty javadoc fields.
* Use <p> to separate description paragraphs.
* End description paragraphs with a period.
* Remove period at the end of field descriptions.

Change-Id: I749e4b821fc855999caddc442ac788fa514386ea
Signed-off-by: Ivan Frade <ifrade@google.com>

Using the | and & operators in boolean conditions results in a warning
from Error Prone:

  [ShortCircuitBoolean]
  Prefer the short-circuiting boolean operators && and || to & and |.
  see https://errorprone.info/bugpattern/ShortCircuitBoolean

Change-Id: I4275c60306e43c74030c4465ba02cb853ad444e1
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Fix all remaining instances of the OperatorPrededence warning, by adding
parentheses to make the precedence explicit.

Change-Id: Ib296dfed09f9be042d0ff0f7fad8214e4dd766b4
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

The TODO comments say "in 5.0", but 5.0 was already released without
resolving them. Remove "in 5.0" on the assumption that the mentioned
improvements still need to be done at some point.

Change-Id: I3eb429803e2266de3fc490e1f3912991c08aa1ad
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

When loading the config, a FileNotFoundException may occur if the file
exists but cannot be read (see [1]). This is the case on Windows with a
virus scanner checking the file. Therefore if the file exists and that
exception is thrown, retry multiple times, similar to how this was
already implemented for IOException.

[1] https://docs.oracle.com/javase/8/docs/api/java/io/FileNotFoundException.html

Bug: 529522
Change-Id: Ic5dc3b7b24bb0005d6256ed00513bc7c0b91e613
Signed-off-by: Michael Keppler <Michael.Keppler@gmx.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

We logged a stack trace if the configured http.cookieFile was missing.
Instead only log a warning.

Bug: 548081
Change-Id: I42e39f5ad8ffce7b43162e5068f60af073b8a126
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

The git config entries "http.cookieFile" and
"http.saveCookies" are correctly evaluated.

Bug: 488572
Change-Id: Icfeeea95e1a5bac3fa4438849d4ac2306d7d5562
Signed-off-by: Konrad Windszus <konrad_w@gmx.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

When Error Prone checks are enabled, the "ClassCanBeStatic" warning is
triggered:

  Inner class is non-static but does not reference enclosing class
  see https://errorprone.info/bugpattern/ClassCanBeStatic

Change-Id: I5a0e3bf0cf8c28176d9c98914c1c0dfab9c5736f
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

This change is needed to implement permission aware ref database in
Gerrit: [1], that is a pre-requisite to re-enable Git v2 protocol in
Gerrit: [2].

Background: Last year Git v2 protocol was enabled in Gerrit. The fact,
that JGit layer was not calling ref advertise filter for Git v2
protocol, introduced security vulnerability.

The lesson learned from this security incident: Gerrit should not rely
on ref advertise filter being called by JGit to implement crictical
security checks. Instead, the idea is to use the same approach as
currently used by Google's internal code on googlesource.com that
didn't suffer from this vulnerability: provide a custom repository to
JGit. The repository provides a RefDatabase that is permission-aware
and will only ever return refs that the user has access to.

However, due to hard coded instanceof operator usages in JGit code
base, some tests in Gerrit are failing with: [1] in place. This change
addresses this problem.

[1] https://gerrit-review.googlesource.com/c/gerrit/+/212874
[2] https://gerrit-review.googlesource.com/c/gerrit/+/226754

Change-Id: I67c0f53ca33b149442e7ee3e51910d19e3f348d5
Signed-off-by: David Ostrovsky <david@ostrovsky.org>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: Ia698cc06aa3fe6cb7903a687db8885f1b83c3bf2
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

If the attributes of FileSnapshot don't detect modification of a
packfile read the packfile's checksum and compare it against the
checksum cached in the loaded packfile.

Since reading the checksum needs less IO than reloading the complete
packfile this may help to reduce the overhead to detect modficiation
when a gc completes while ObjectDirectory scans for packfiles in another
thread.

Bug: 546891
Change-Id: I9811b497eb11b8a85ae689081dc5d949ca8c4be5
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

If
- pack.waitPreventRacyPack = true (default is false)
- packfile size > pack.minSizePreventRacyPack (default is 100 MB)
wait after a new packfile was written and before it is opened until it
cannot be racy anymore.

If a new packfile is accessed while it's still racy at least the pack's
index will be reread by ObjectDirectory.scanPacksImpl(). Hence it may
save resources to wait one tick of the file system timer to avoid this
reloading. On filesystems with a coarse timestamp resolution it may be
beneficial to skip this wait for small packfiles.

Bug: 546891
Change-Id: I0e8bf3d7677a025edd2e397dd2c9134ba59b1a18
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Initialize it using the repository's config already in the constructor.

Change-Id: I4ea620a7db72956e7109f739990f09644640206b
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This allows to verify the expected behavior in
FileSnapshotTest#testSimulatePackfileReplacement and enables extending
FileSnapshot for packfiles to read the packfile's checksum as another
criterion to detect modifications without reading the full content.

Also add another field capturing the result of the last check if
lastModified was racily clean.

Remove unnecessary determination of raciness in the constructor. It was
determined twice in all relevant cases.

Change-Id: I100a2f49d7949693d7b72daa89437e166f1dc107
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This resolves a regression introduced in fef78212.

Change-Id: Ibb4521635a87012520566efc70870c59d11be874
Signed-off-by: Marc Strapetz <marc.strapetz@syntevo.com>

Offer a version of findBranchesReachableFrom method with progress
monitor callback. This is required to allow UI clients to cancel long
running operations and show progress.

Bug: 547642
Change-Id: I31d1de54dbaa6ffb11e03da4c447963e8defa1d0
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>

Due to finite filesystem timestamp resolution the last modified
timestamp of files cannot detect file changes which happened in the
immediate past (less than one filesystem timer tick ago).

Some filesystems expose unique file identifiers, e.g. inodes in Posix
filesystems which are named filekeys in Java's BasicFileAttributes. Use
them as another means to detect file modifications based on stat
information.

Running git gc on a repository yields a new packfile with the same id as
a packfile which existed before the gc if these packfiles contain the
same set of objects. The content of the old and the new packfile might
differ if a different PackConfig was used when writing the packfile.
Considering filekeys in FileSnapshot may help to detect such packfile
modifications.

Bug: 546891
Change-Id: I711a80328c55e1a31171d540880b8e80ec1fe095
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>