Commit Graph

4667 Commits

Author SHA1 Message Date
Matthias Sohn d63eb16a1e Merge "Require-Bundle com.jcraft.jsch replaced by Import-Package statement" 2016-08-08 18:43:56 -04:00
Jens Offenbach e2cb2f8afd Require-Bundle com.jcraft.jsch replaced by Import-Package statement
Bug: 359288
Change-Id: Ifbbf953f5389c6bd3ba960b598c0e92656b522e3
Signed-off-by: Jens Offenbach <wolle5050@gmx.de>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
2016-08-09 00:10:18 +02:00
Jonathan Nieder 3b0b7677ff Merge changes Ib0d8c294,Idfb83482
* changes:
  Shallow fetch: Pass along "shallow"s in unparsed-wants case, too
  Shallow fetch: Pass a DepthWalk to PackWriter

Change-Id: I7d1c3b4d0b7ebc254b53404d1618522b0174ac23
2016-08-08 13:50:57 -07:00
Jonathan Nieder b16e207742 Shallow fetch: Pass along "shallow"s in unparsed-wants case, too
Since 84d2738ff2 (Don't skip want validation when the client sends no
haves, 2013-06-21), this branch is not taken.  Process the
"shallow"s anyway as a defensive measure in case the code path gets
revived.

Change-Id: Idfb834825d77f51e17191c1635c9d78c78738cfd
Signed-off-by: Jonathan Nieder <jrn@google.com>
2016-08-08 16:49:37 -04:00
Jonathan Nieder f84370feaa Shallow fetch: Pass a DepthWalk to PackWriter
d385a7a5e5 (Shallow fetch: Respect "shallow" lines, 2016-08-03) forgot
that UploadPack wasn't passing a DepthWalk to PackWriter in the first
place.  As a result, shallow clones fail:

  java.lang.IllegalArgumentException: Shallow packs require a DepthWalk
        at org.eclipse.jgit.internal.storage.pack.PackWriter.preparePack(PackWriter.java:756)
        at org.eclipse.jgit.transport.UploadPack.sendPack(UploadPack.java:1497)
        at org.eclipse.jgit.transport.UploadPack.sendPack(UploadPack.java:1381)
        at org.eclipse.jgit.transport.UploadPack.service(UploadPack.java:774)
        at org.eclipse.jgit.transport.UploadPack.upload(UploadPack.java:667)
        at org.eclipse.jgit.http.server.UploadPackServlet.doPost(UploadPackServlet.java:191)

Change-Id: Ib0d8c2946eebfea910a2b767fb92e23da15d4749
2016-08-08 16:48:29 -04:00
Matthias Sohn b4d3338225 Fix non-parameterized generic type warning
Change-Id: Ib857166f64420aebf7c31d72825cac44bd770dbd
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
2016-08-08 02:43:09 -04:00
Matthias Sohn 63bfd9b976 Merge "Add path src/ to source path in build.properties" 2016-08-08 02:42:22 -04:00
Christian Halstrick 2c5c035e62 Merge "Skip cleaning inner repositories by default in CleanCommand" 2016-08-07 09:37:48 -04:00
Christian Halstrick cb3bd8ea84 Merge "Add testCleanDirsWithSubmodule test to CleanCommandTest" 2016-08-07 09:37:22 -04:00
Matthias Sohn 8141140922 Add path src/ to source path in build.properties
This fixes the warning "src/ is missing from source.."

Change-Id: I166e3a6a3d5230e4110d3283ec4dbc7d1dfe6732
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
2016-08-06 19:12:06 -04:00
Jonathan Nieder 1c245da5ac Merge changes I27961679,I91be6165,If0dbd562
* changes:
  LfsProtocolServlet: Allow access to objects in request
  LfsProtocolServlet: Allow getLargeFileRepository to raise exceptions
  Remove references to org.eclipse.jgit.java7
2016-08-05 20:36:09 -04:00
Terry Parker e426aa8b90 Shallow fetch/clone: Make --depth mean the total history depth
cgit changed the --depth parameter to mean the total depth of history
rather than the depth of ancestors to be returned [1]. JGit still uses
the latter meaning, so update it to match cgit.

depth=0 still means a non-shallow clone. depth=1 now means only the
wants rather than the wants and their direct parents.

This is accomplished by changing the semantic meaning of "depth" in
UploadPack and PackWriter to mean the total depth of history desired,
while keeping "depth" in DepthWalk.{RevWalk,ObjectWalk} to mean
the depth of traversal. Thus UploadPack and PackWriter always
initialize their DepthWalks with "depth-1".

[1] upload-pack: fix off-by-one depth calculation in shallow clone
https://code.googlesource.com/git/+/682c7d2f1a2d1a5443777237450505738af2ff1a

Change-Id: I87ed3c0f56c37e3491e367a41f5e555c4207ff44
Signed-off-by: Terry Parker <tparker@google.com>
2016-08-05 17:27:30 -07:00
Terry Parker d385a7a5e5 Shallow fetch: Respect "shallow" lines
When fetching from a shallow clone, the client sends "have" lines
to tell the server about objects it already has and "shallow" lines
to tell where its local history terminates. In some circumstances,
the server fails to honor the shallow lines and fails to return
objects that the client needs.

UploadPack passes the "have" lines to PackWriter so PackWriter can
omit them from the generated pack. UploadPack processes "shallow"
lines by calling RevWalk.assumeShallow() with the set of shallow
commits. RevWalk creates and caches RevCommits for these shallow
commits, clearing out their parents. That way, walks correctly
terminate at the shallow commits instead of assuming the client has
history going back behind them. UploadPack converts its RevWalk to an
ObjectWalk, maintaining the cached RevCommits, and passes it to
PackWriter.

Unfortunately, to support shallow fetches the PackWriter does the
following:

  if (shallowPack && !(walk instanceof DepthWalk.ObjectWalk))
    walk = new DepthWalk.ObjectWalk(reader, depth);

That is, when the client sends a "deepen" line (fetch --depth=<n>)
and the caller has not passed in a DepthWalk.ObjectWalk, PackWriter
throws away the RevWalk that was passed in and makes a new one. The
cleared parent lists prepared by RevWalk.assumeShallow() are lost.
Fortunately UploadPack intends to pass in a DepthWalk.ObjectWalk.
It tries to create it by calling toObjectWalkWithSameObjects() on
a DepthWalk.RevWalk. But it doesn't work: because DepthWalk.RevWalk
does not override the standard RevWalk#toObjectWalkWithSameObjects
implementation, the result is a plain ObjectWalk instead of an
instance of DepthWalk.ObjectWalk.

The result is that the "shallow" information is thrown away and
objects reachable from the shallow commits can be omitted from the
pack sent when fetching with --depth from a shallow clone.

Multiple factors collude to limit the circumstances under which this
bug can be observed:

1. Commits with depth != 0 don't enter DepthGenerator's pending queue.
   That means a "have" cannot have any effect on DepthGenerator unless
   it is also a "want".

2. DepthGenerator#next() doesn't call carryFlagsImpl(), so the
   uninteresting flag is not propagated to ancestors there even if a
   "have" is also a "want".

3. JGit treats a depth of 1 as "1 past the wants".

Because of (2), the only place the UNINTERESTING flag can leak to a
shallow commit's parents is in the carryFlags() call from
markUninteresting(). carryFlags() only traverses commits that have
already been parsed: commits yet to be parsed are supposed to inherit
correct flags from their parent in PendingGenerator#next (which
doesn't happen here --- that is (2)). So the list of commits that have
already been parsed becomes relevant.

When we hit the markUninteresting() call, all "want"s, "have"s, and
commits to be unshallowed have been parsed. carryFlags() only
affects the parsed commits. If the "want" is a direct parent of a
"have", then it carryFlags() marks it as uninteresting. If the "have"
was also a "shallow", then its parent pointer should have been null
and the "want" shouldn't have been marked, so we see the bug. If the
"want" is a more distant ancestor then (2) keeps the uninteresting
state from propagating to the "want" and we don't see the bug. If the
"shallow" is not also a "have" then the shallow commit isn't parsed
so (2) keeps the uninteresting state from propagating to the "want
so we don't see the bug.

Here is a reproduction case (time flowing left to right, arrows
pointing to parents). "C" must be a commit that the client
reports as a "have" during negotiation. That can only happen if the
server reports it as an existing branch or tag in the first round of
negotiation:

  A <-- B <-- C <-- D

First do

  git clone --depth 1 <repo>

which yields D as a "have" and C as a "shallow" commit. Then try

  git fetch --depth 1 <repo> B:refs/heads/B

Negotiation sets up: have D, shallow C, have C, want B.
But due to this bug B is marked as uninteresting and is not sent.

Change-Id: I6e14b57b2f85e52d28cdcf356df647870f475440
Signed-off-by: Terry Parker <tparker@google.com>
2016-08-05 18:37:36 -04:00
David Pursehouse 584035a5fb LfsProtocolServlet: Allow access to objects in request
Classes implementing the LFS servlet should be able to inspect the
objects given in the request.

Add a getObjects method. Make the LfsObject class public, and add
accessor methods.

Change-Id: I27961679f620eb3a89dc8521aadd4ea2f936c60e
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-08-05 11:22:27 +09:00
David Pursehouse 571c9f5fd6 LfsProtocolServlet: Allow getLargeFileRepository to raise exceptions
According to the specification [1] the server may return the following
HTTP error responses:

- 403: The user has read, but not write access.
- 404: The repository does not exist for the user.
- 422: Validation error with one or more of the objects in the request.

In the current implementation, however, getLargeFileRepository can only
return null to indicate an error. This results in the error code:

- 503: Service Unavailable

being returned to the client regardless of what the actual reason was.

Add exception classes to cover these cases, derived from a common base
exception, and change the specification of getLargeFileRepository to throw
the base exception.

In LfsProtocolServlet#post, handle the new exceptions and send back the
appropriate HTTP responses as mentioned above.

The specification also mentions several other optional response codes (406,
429, 501, and 509) but these are not implemented in this commit. It should
be trivial to implement them in follow-up commits.

[1] https://github.com/github/git-lfs/blob/master/docs/api/v1/http-v1-batch.md#response-errors

Change-Id: I91be6165bcaf856d0cefc533882330962e2fc9b2
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-08-05 11:22:27 +09:00
David Pursehouse 1ce24d46a6 Remove references to org.eclipse.jgit.java7
The bundle org.eclipse.jgit.java7 was removed in 4.0.

Remove references to it from the README.md.

Remove reference to it from org.eclipse.jgit.test/.project, which
causes an error message when opening the project in Eclipse:

  Resource '/org.eclipse.jgit.java7' does not exist.

Change-Id: If0dbd562dcd60550bec3c0f793289474b7624bce
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-08-05 11:22:27 +09:00
Jonathan Nieder 958684edef Merge changes from topic 'shallowClone'
* changes:
  RevWalk: Make fields available to DepthWalk
  Shallow fetch: avoid sending unneeded blobs
2016-08-04 20:26:53 -04:00
Terry Parker 2a7897bb4c RevWalk: Make fields available to DepthWalk
DepthWalk needs to override toObjectWalkWithSameObjects() and thus
needs to be able to directly set the objects and freeFlags fields, so
make them package private.

Change-Id: I24561b82c54ba3d6522582ca25105b204d777074
Signed-off-by: Terry Parker <tparker@google.com>
2016-08-04 17:20:27 -07:00
Terry Parker 7edf05530d Shallow fetch: avoid sending unneeded blobs
When doing an incremental fetch from JGit, "have" commits are marked
as "uninteresting". In a non-shallow fetch, when the RevWalk hits an
"uninteresting" commit it marks the commit's corresponding tree as
uninteresting. That has the effect of dropping those trees and all the
trees and blobs they reference out of the thin pack returned to the
client.

However, shallow fetches use a DepthWalk to limit the RevWalk, which
nearly always causes the RevWalk to terminate before encountering the
"have" commits. As a result the pack created for the incremental fetch
never encounters "uninteresting" tree objects and thus includes
duplicate objects that it knows the client already has.

Change-Id: I7b1f7c3b0d83e04d34cd2fa676f1ad4fec904c05
Signed-off-by: Terry Parker <tparker@google.com>
2016-08-04 17:20:23 -07:00
Terry Parker a8f15b7b2f Merge "PackWriterTest: Improve readability" 2016-08-04 19:19:07 -04:00
Terry Parker 9843489cb8 PackWriterTest: Improve readability
Add wants() and haves() static utility functions to improve readability.


Change-Id: I4d44e17a9af97c0203e2ebe112eabb1f67d272a6
Signed-off-by: Terry Parker <tparker@google.com>
2016-08-04 14:59:05 -07:00
Matthaus Owens e1ffab1cac Skip cleaning inner repositories by default in CleanCommand
Previously jgit would attempt to clean git repositories that had not
been committed by calling a non-recursive delete on them, which would
fail as they are directories. This commit addresses that issue in the
following ways.
Repositories are skipped in a default clean, similarly to cgit and only
cleaned when the force flag is applied. When the force flag is applied
repositories are deleted using a recursive delete call. The force flag
and setForce method are added here to CleanCommand to support this
change.

Bug: 498367
Change-Id: Ib6cfff65a033d0d0f76395060bf76719e13fc467
Signed-off-by: Matthaus Owens <matthaus@puppetlabs.com>
2016-08-04 13:38:52 -07:00
Matthaus Owens 0ee89f01be Add testCleanDirsWithSubmodule test to CleanCommandTest
This commit adds some test coverage to cleaning a repository with a
submodule, which did not previously exist.

Bug: 498367
Change-Id: Ia5c4e4cc53488800dd486f8556dc57656783f1c4
Signed-off-by: Matthaus Owens <matthaus@puppetlabs.com>
2016-08-04 13:04:17 +01:00
Dave Borowitz d6fe52e914 DiffFormatter: Support setting a reader without a repo
Change-Id: I575cdb9c0a9a341b79ef5e3c7a35e68cde142540
2016-08-03 16:24:37 -04:00
Jonathan Nieder 23b1405484 Merge "RefSpec: Make WildcardMode public" 2016-07-28 14:47:05 -04:00
Stefan Beller 647bf67f8d RefSpec: Make WildcardMode public
We have to be able to access the enum from outside the package as part of
the API.

Change-Id: I4bdc6bd53a14237c5f4fb9397ae850f9a24c4cfb
Signed-off-by: Stefan Beller <sbeller@google.com>
2016-07-28 11:29:38 -07:00
David Pursehouse f703a5eb2c Fix typo in email address in copyright headers
Change-Id: Ib7b73d7d37574682bb58f969822c842e4e579233
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-28 16:05:22 +09:00
David Pursehouse ddb12b003f LfsServerTest: Treat response body as UTF-8 when decoding error message
Change-Id: I495f0b60b7128fff27502641e6a5d05f888d4e8a
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-28 12:17:45 +09:00
David Pursehouse bb9988c236 LfsProtocolServlet: Pass request and path to getLargeFileRepository
Passing the request and path to the method will allow implementations
to have more control over determination of the backend, for example:

- return different backends for different requests
- accept or refuse requests based on request characteristics
- etc

Change-Id: I1ec6ec54c91a5f0601b620ed18846eb4a3f46783
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-27 15:54:03 +09:00
David Pursehouse e27eab26e2 FileLfsServlet: Include error message in response body
According to the specification [1], the error response body must
include the error message in json format.

[1] https://github.com/github/git-lfs/blob/master/docs/api/v1/http-v1-batch.md#response-errors

Change-Id: I79e7a841d230fdedefa53b9c6d2d477e81e1f9e6
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-27 11:07:05 +09:00
David Pursehouse 2e652aebab FileLfsServlet: Return HTTP 422 instead of 400
According to the specification [1], the error response status code
should be 422 when there is a validation error with one or more of
the objects in the request

[1] https://github.com/github/git-lfs/blob/master/docs/api/v1/http-v1-batch.md#response-errors

Change-Id: Id03fe00a2109b896d9a154228a14a33bce5accc3
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-27 11:01:14 +09:00
David Pursehouse b8d861bfd5 Repository: Log negative useCnt message together with stack trace
The message "close() called when useCnt is already zero" is logged with
level warning, and then if debug logging is enabled, the stack trace is
logged separately with level debug.

Log the message and the stack trace in the same call, so that they always
appear together in the output rather than potentially interleaved with
other log statements.

Change-Id: I1b5c1557ddc2d19f3f5b29baec96e62bc467d88a
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-26 18:58:17 +09:00
David Pursehouse c15903ea3e MergeFormatter: Suppress warning about unchecked conversion
The warning can be fixed by adding a type to the argument, but doing so
breaks the API and previous attempts to fix it in that way [1, 2] were
reverted [3, 4].

[1] https://git.eclipse.org/r/#/c/45709/
[2] https://git.eclipse.org/r/#/c/66602/
[3] https://git.eclipse.org/r/#/c/49400/
[4] https://git.eclipse.org/r/#/c/66659/

Change-Id: I01dd52e09da24f70d408ffa96e21c129a79041ea
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-26 18:58:17 +09:00
David Pursehouse 0d872a0837 Annotate Sets#of with @SafeVarArgs to prevent heap pollution warning
This prevents the warning:

  Potential heap pollution via varargs parameter

The method doesn't do any casting of types that would cause the heap
pollution, so it should be safe to add @SafeVarArgs.

See [1] for information about this warning.

[1] http://stackoverflow.com/a/12462259/381622

Change-Id: Ic6d252915ea44b4f1c385afecb98906cd2c54382
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-26 18:58:17 +09:00
David Pursehouse eb7a93bb2a Archive: Make project name consistent with other subprojects'
Change-Id: I8341f3340d8129b4f966d541097269210fbf65d2
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-26 18:58:17 +09:00
David Pursehouse 4528d5f56d Ignore 'The value of exception parameter is not used' warning
Change-Id: I50407e4a33e35b718ca40503fdd436f1f9f70fba
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-26 10:16:49 +09:00
David Pursehouse 053684ac24 Update links to LFS API documentation
The location of the API v1 documentation has changed. Update the
links accordingly.

Change-Id: If0148a0b573c474bbe157fcb7e6674c0055fe8b4
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-26 10:16:49 +09:00
David Pursehouse 0be8021819 Merge branch 'stable-4.4'
* stable-4.4:
  JGit v4.4.1.201607150455-r
  RefDirectory: remove ref lock file for following ref dir removal

Change-Id: Ifc8a782efd7f2f991e70ad2a3691a8dba66c7554
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>
2016-07-26 10:09:35 +09:00
Stefan Beller a2d3c376a6 RefSpecs: allow construction of weird wildcarded RefSpecs
Gerrit's superproject subscription feature uses RefSpecs to formalize
the ACLs of when the superproject subscription feature is allowed.

As this is a slightly different use case than describing a local/remote
pair of refs, we need to be more permissive. Specifically we want to allow:

    refs/heads/*
    refs/heads/*:refs/heads/master
    refs/heads/master:refs/heads/*

Introduce a new constructor, that allows constructing these RefSpecs.

Change-Id: I46c0bea9d876e61eb2c8d50f404b905792bc72b3
Signed-off-by: Stefan Beller <sbeller@google.com>
2016-07-25 10:10:06 -07:00
Stefan Beller 1556ca740b RefSpec: reject refs ending in '/'
We had a case in Gerrits superproject subscriptions where
'refs/heads/' was configured with the intention to mean 'refs/heads/*'.

The first expression lacks the '*', which is why it is not considered
a wildcard but it was considered valid and so was not found early to be
a typo.

Refs are not allowed to end with '/' anyway, so add a check for that.

Change-Id: I3ffdd9002146382acafb4fbc310a64af4cc1b7a9
Signed-off-by: Stefan Beller <sbeller@google.com>
2016-07-25 10:10:06 -07:00
Terry Parker e9e2f7e6b5 Merge "Push implementation of option strings" 2016-07-22 19:27:20 -04:00
Dan Wang 7f9fb80002 Push implementation of option strings
Example usage:
$ ./jgit push \
  --push-option "Reviewer=j.doe@example.org" \
  --push-option "<arbitrary string>" \
  origin HEAD:refs/for/master
Stefan Beller has also made an equivalent change to CGit:
http://thread.gmane.org/gmane.comp.version-control.git/299872

Change-Id: I6797e50681054dce3bd179e80b731aef5e200d77
Signed-off-by: Dan Wang <dwwang@google.com>
2016-07-22 15:40:54 -07:00
Dave Borowitz ecb2aa0503 DfsObjDatabase: Add lazy last modified method to PackList
Change-Id: Id045f162fa584ea14da29a9df58a42c53a78dc15
2016-07-19 13:18:13 -04:00
Dave Borowitz e790ec3fb1 Merge changes I159e9154,I06c722b2
* changes:
  DfsObjectDatabase: Expose PackList and move markDirty there
  Invalidate DfsObjDatabase pack list when refs are updated
2016-07-19 10:51:52 -04:00
Dave Borowitz 0f1c361e62 DfsObjectDatabase: Expose PackList and move markDirty there
What's invalidated when an object database is "dirty" is not the whole
database, but rather a specific list of packs. If there is a race
between getting the pack list and setting the volatile dirty flag
where the packs are rescanned, we don't need to mark the new pack list
as dirty.

This is a fine point that only really applies if the decision of
whether or not to mark dirty actually requires introspecting the pack
list (say, its timestamps). The general operation of "take whatever
is the current pack list and mark it dirty" may still be inherently
racy, but the cost is not so high.

Change-Id: I159e9154bd8b2d348b4e383627a503e85462dcc6
2016-07-18 15:57:41 -04:00
Dan Wang 0d2a7b7737 BatchRefUpdate: Remove unused namesToCheck variable
This variable has been populated and never used since it was
introduced in commit 5cf53fdacf
(Speed up clone/fetch with large number of refs, 2013-02-18).
Noted by FindBugs:
"BatchRefUpdate.java:359, UC_USELESS_OBJECT, Priority: Normal"

Change-Id: I7aacb49540aaee4a83db3d38b15633bb6c4773d0
Signed-off-by: Dan Wang <dwwang@google.com>
2016-07-15 20:09:43 -04:00
Matthias Sohn df479df176 JGit v4.4.1.201607150455-r
Change-Id: I61dbc29a962c8185fb356fe1ca30a1e673166d47
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
2016-07-15 10:54:36 +02:00
Christian Halstrick eaedbc3980 Merge "RefDirectory: remove ref lock file for following ref dir removal" into stable-4.4 2016-07-15 04:43:53 -04:00
Matthias Sohn 9a4e8de467 Fix AppServer build errors in Eclipse with <4.6 target platforms
9aa3748 added dummy implementations for loadRoleInfo() and
loadUserInfo() to class MappedLoginService to fix compile errors in
Eclipse when using 4.6 target platform which brings Jetty 9.3 adding
these two methods. Unfortunately this causes errors when using non 4.6
target platform coming with an older Jetty version. Fix this by
extracting the anonymous subclass of MappedLoginService which allows to
suppress the unused private method errors in Eclipse.

Change-Id: I75baeea7ff4502ce9ef2b541b3c0555da5535d79
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
2016-07-14 22:59:14 +02:00
Dave Borowitz 18e9db306b Invalidate DfsObjDatabase pack list when refs are updated
Currently, there is a race where a user of a DfsRepository in a single
thread may get unexpected MissingObjectExceptions trying to look up an
object that appears as the current value of a ref:

1. Thread A scans packs before scanning refs, for example by reading
   an object by SHA-1.
2. Thread B flushes an object and updates a ref to point to that
   object.
3. Thread A looks up the ref updated in (2). Since it is scanning refs
   for the first time, it sees the new object SHA-1.
4. Thread A tries to read the object it found in (3), using the cached
   pack list it got from (1). The object appears missing.

Allow implementations to work around this by marking the object
database's current pack list as "dirty." A dirty pack list means that
DfsReader will rescan packs and try again if a requested object is
missing. Implementations should mark objects as dirty any time the ref
database reads or scans refs that might be newer than a previously
cached pack list.

Change-Id: I06c722b20c859ed1475628ec6a2f6d3d6d580700
2016-07-14 15:58:14 -04:00