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Matthias Sohn b513b77477 Measure file timestamp resolution used in FileSnapshot 
FileSnapshot.notRacyClean() assumed a worst case filesystem timestamp
resolution of 2.5 sec (FAT has a resolution of 2 sec). Instead measure
timestamp resolution to avoid unnecessary IO caused by false positives
in detecting the racy git problem caused by finite filesystem timestamp
resolution [1].

Cache the measured resolution per FileStore since timestamp resolution
depends on the respective filesystem type. If timestamp resolution
cannot be measured or fails due to an exception fallback to the worst
case FAT timestamp resolution and avoid caching this value.

Add a 10% safety margin in FileSnapshot.notRacyClean(), though running
FsTest.testFsTimestampResolution() 1000 times which is not using a
safety margin didn't fail on Mac using APFS and Java 8, 11, 12.

Measured Java file timestamp resolution: [2]

[1] https://github.com/git/git/blob/master/Documentation/technical/racy-git.txt
[2] https://docs.google.com/spreadsheets/d/1imy0y6WmRqBf0kjCxzxj2X7M50eIVfa7oaUIzEOHmjo

Bug: 546891
Change-Id: I493f3b57b6b306285ffa7d392339d253e5966ab8
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
 		2019-05-22 08:13:22 +02:00
.mvn Configure max heap size for Maven build 2016-12-09 11:02:10 +01:00
Documentation/technical reftable: explicitly store update_index per ref 2017-08-21 15:39:08 -07:00
lib Merge branch 'stable-5.0' into stable-5.1 2018-08-31 16:11:37 +09:00
org.eclipse.jgit Measure file timestamp resolution used in FileSnapshot 2019-05-22 08:13:22 +02:00
org.eclipse.jgit.ant Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.ant.test Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.archive Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.http.apache Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.http.server Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.http.test Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.junit Measure file timestamp resolution used in FileSnapshot 2019-05-22 08:13:22 +02:00
org.eclipse.jgit.junit.http Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.lfs Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.lfs.server Fix API problem filters 2019-05-22 08:03:29 +02:00
org.eclipse.jgit.lfs.server.test Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.lfs.test Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.packaging Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.pgm Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.pgm.test Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
org.eclipse.jgit.test Measure file timestamp resolution used in FileSnapshot 2019-05-22 08:13:22 +02:00
org.eclipse.jgit.ui Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00
tools Bazel: Stop using native.git_repository 2019-03-03 13:15:19 +09:00
.gitattributes Initial JGit contribution to eclipse.org 2009-09-29 16:47:03 -07:00
.gitignore git ignore .DS_Store 2017-07-28 11:09:47 +01:00
.mailmap Update .mailmap 2018-06-27 13:42:29 +09:00
BUILD Bazel: Support building with Java 9 2018-02-07 17:51:35 -05:00
CONTRIBUTING.md Update SUBMITTING_PATCHES 2014-07-20 17:44:53 -04:00
LICENSE Clean up LICENSE file 2010-07-02 14:52:49 -07:00
README.md Update minimum JDK version in README 2017-02-10 18:47:39 -04:00
WORKSPACE Merge branch 'stable-5.0' into stable-5.1 2018-08-31 16:11:37 +09:00
pom.xml Prepare 5.1.8-SNAPSHOT builds 2019-04-20 10:51:17 +02:00

README.md

Java Git

An implementation of the Git version control system in pure Java.

This package is licensed under the EDL (Eclipse Distribution License).

JGit can be imported straight into Eclipse, built and tested from there, but the automated builds use Maven.

  • org.eclipse.jgit

    A pure Java library capable of being run standalone, with no additional support libraries. It provides classes to read and write a Git repository and operate on a working directory.

    All portions of JGit are covered by the EDL. Absolutely no GPL, LGPL or EPL contributions are accepted within this package.

  • org.eclipse.jgit.ant

    Ant tasks based on JGit.

  • org.eclipse.jgit.archive

    Support for exporting to various archive formats (zip etc).

  • org.eclipse.jgit.http.apache

    Apache httpclient support

  • org.eclipse.jgit.http.server

    Server for the smart and dumb Git HTTP protocol.

  • org.eclipse.jgit.pgm

    Command-line interface Git commands implemented using JGit ("pgm" stands for program).

  • org.eclipse.jgit.packaging

    Production of Eclipse features and p2 repository for JGit. See the JGit Wiki on why and how to use this module.

Tests

  • org.eclipse.jgit.junit

    Helpers for unit testing

  • org.eclipse.jgit.test

    Unit tests for org.eclipse.jgit

  • org.eclipse.jgit.ant.test

  • org.eclipse.jgit.pgm.test

  • org.eclipse.jgit.http.test

  • org.eclipse.jgit.junit.test

    No further description needed

Warnings/Caveats

  • Native smbolic links are supported, provided the file system supports them. For Windows you must have Windows Vista/Windows 2008 or newer, use a non-administrator account and have the SeCreateSymbolicLinkPrivilege.

  • Only the timestamp of the index is used by jgit if the index is dirty.

  • JGit requires at least a Java 8 JDK.

  • CRLF conversion is performed depending on the core.autocrlf setting, however Git for Windows by default stores that setting during installation in the "system wide" configuration file. If Git is not installed, use the global or repository configuration for the core.autocrlf setting.

  • The system wide configuration file is located relative to where C Git is installed. Make sure Git can be found via the PATH environment variable. When installing Git for Windows check the "Run Git from the Windows Command Prompt" option. There are other options like Eclipse settings that can be used for pointing out where C Git is installed. Modifying PATH is the recommended option if C Git is installed.

  • We try to use the same notation of $HOME as C Git does. On Windows this is often not the same value as the user.home system property.

Package Features

  • org.eclipse.jgit/

    • Read loose and packed commits, trees, blobs, including deltafied objects.

    • Read objects from shared repositories

    • Write loose commits, trees, blobs.

    • Write blobs from local files or Java InputStreams.

    • Read blobs as Java InputStreams.

    • Copy trees to local directory, or local directory to a tree.

    • Lazily loads objects as necessary.

    • Read and write .git/config files.

    • Create a new repository.

    • Read and write refs, including walking through symrefs.

    • Read, update and write the Git index.

    • Checkout in dirty working directory if trivial.

    • Walk the history from a given set of commits looking for commits introducing changes in files under a specified path.

    • Object transport Fetch via ssh, git, http, Amazon S3 and bundles. Push via ssh, git and Amazon S3. JGit does not yet deltify the pushed packs so they may be a lot larger than C Git packs.

    • Garbage collection

    • Merge

    • Rebase

    • And much more

  • org.eclipse.jgit.pgm/

    • Assorted set of command line utilities. Mostly for ad-hoc testing of jgit log, glog, fetch etc.

  • org.eclipse.jgit.ant/

    • Ant tasks

  • org.eclipse.jgit.archive/

    • Support for Zip/Tar and other formats

  • org.eclipse.http.*/

    • HTTP client and server support

Missing Features

There are some missing features:

  • gitattributes support

Support

Post question, comments or patches to the jgit-dev@eclipse.org mailing list. You need to be subscribed to post, see here:

https://dev.eclipse.org/mailman/listinfo/jgit-dev

Contributing

See the EGit Contributor Guide:

http://wiki.eclipse.org/EGit/Contributor_Guide

About Git

More information about Git, its repository format, and the canonical C based implementation can be obtained from the Git website:

http://git-scm.com/