### Get Help for JGit Version Command

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

View the help message for a specific JGit command, such as 'version', to understand its available flags and usage.

```bash
prompt$ ./jgit version -h
jgit version [--help (-h)]

 --help (-h) : display this help text
```

--------------------------------

### Registering BouncyCastleProvider in EGit

Source: https://github.com/eclipse-jgit/jgit/wiki/New-and-Noteworthy-7.0

Example of how to manually register the BouncyCastleProvider security provider, as required by JGit 7.0.0 for certain GPG key types.

```java
import java.security.Security;
import org.bouncycastle.jce.provider.BouncyCastleProvider;

// ...

// Register BouncyCastleProvider if needed for AES/OCB support
if (Security.getProvider(BouncyCastleProvider.PROVIDER_NAME) == null) {
	Security.addProvider(new BouncyCastleProvider());
}
```

--------------------------------

### Get Commit Log using Porcelain API

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Use the LogCommand to iterate over the commit history. Ensure a Git instance is initialized with a Repository.

```java
Git git = new Git(db);
Iterable<RevCommit> log = git.log().call();
```

--------------------------------

### Get a Git Reference

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Query for a reference to HEAD, such as the master branch reference.

```java
Ref HEAD = repository.getRef("refs/heads/master");
```

--------------------------------

### View JGit Branch Summary

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Get a summary of repository branches, their revisions, and commit message first lines using the 'branch -v' command.

```bash
prompt$ ./jgit branch -v
  master       4d4adfb Git Project import: don't hide but gray out existing projects
* traceHistory 6b9fe04 [historyView] Add trace instrumentation
```

--------------------------------

### Prepare Virtual Environment

Source: https://github.com/eclipse-jgit/jgit/blob/master/tools/maven-central/README.md

Sets up a virtual environment using pipenv for the download_release.py script. Ensure Python 3.14 is available.

```bash
cd tools/maven-central
pipenv --python 3.14
pipenv sync
```

--------------------------------

### Initialize Git Repository

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Initializes a new Git repository. The 'dest' attribute specifies the path, and 'bare' determines if it's a bare repository.

```xml
<git-init />
```

--------------------------------

### Build JGit CLI

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Build the jgit binary using Maven. Ensure you have the EGit git repository cloned and ready.

```bash
~/src/jgit$ mvn clean install
```

--------------------------------

### List Common JGit Commands

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Run JGit with no arguments to display a list of the most commonly used commands and their brief descriptions.

```bash
prompt$ ./jgit
jgit --git-dir GIT_DIR --help (-h) --show-stack-trace command [ARG ...]

The most commonly used commands are:
 branch   List, create, or delete branches
 clone    Clone a repository into a new directory
 commit   Record changes to the repository
 daemon   Export repositories over git://
 diff     Show diffs
 fetch    Update remote refs from another repository
 init     Create an empty git repository
 log      View commit history
 push     Update remote repository from local refs
 rm       Stop tracking a file
 tag      Create a tag
 version  Display the version of jgit
```

--------------------------------

### Dummy Files for Backward Compatibility

Source: https://github.com/eclipse-jgit/jgit/blob/master/Documentation/technical/reftable.md

To ensure backward compatibility with older clients, reftable-enabled repositories must contain specific dummy files and directories.

```text
.git/HEAD, a regular file containing ref: refs/heads/.invalid
.git/refs/, a directory
.git/refs/heads, a regular file
```

--------------------------------

### Find Children of a Commit

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

This Java snippet uses PlotWalk to find and process commits starting from a root commit. It's useful for visualizing commit history.

```java
PlotWalk revWalk = new PlotWalk(repo());
ObjectId rootId = (branch==null)?repo().resolve(HEAD):branch.getObjectId();
RevCommit root = revWalk.parseCommit(rootId);
revWalk.markStart(root);

PlotCommitList<PlotLane> plotCommitList = new PlotCommitList<PlotLane>();
plotCommitList.source(revWalk);
plotCommitList.fillTo(Integer.MAX_VALUE);
return revWalk;
```

--------------------------------

### Restrict RevWalk Graph Traversal

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Reduces memory usage by limiting the RevWalk traversal to only necessary commits. Mark the start commit and uninteresting commits to optimize the walk.

```java
RevWalk
walk = new RevWalk(repository);
ObjectId
from = repository.resolve("refs/heads/master");
ObjectId
to = repository.resolve("refs/remotes/origin/master");

walk.markStart(walk.parseCommit(from));
walk.markUninteresting(walk.parseCommit(to));

//	...
```

--------------------------------

### Launch Graphical Log Viewer

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Open the graphical log tool to visualize the revision graph and commit details. This command launches a GUI window.

```bash
prompt$ ./jgit glog
```

--------------------------------

### Index Block Format

Source: https://github.com/eclipse-jgit/jgit/blob/master/Documentation/technical/reftable.md

Defines the structure of an index block, starting with a block type 'i', followed by block length, index records, restart offsets, and restart count. This block is part of the ref index.

```plaintext
'i'
uint24( block_len )
index_record+
uint24( restart_offset )+
uint16( restart_count )

padding?
```

--------------------------------

### Add Files to Index using Porcelain API

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Use the AddCommand to add files or patterns to the Git index. Ensure a Git instance is initialized with a Repository.

```java
Git git = new Git(db);
AddCommand add = git.add();
add.addFilepattern("someDirectory").call();
```

--------------------------------

### Log Record Key Format

Source: https://github.com/eclipse-jgit/jgit/blob/master/Documentation/technical/reftable.md

Illustrates the structured key format for log records, combining the reference name with a reversed 64-bit update index for sorting purposes.

```text
ref_name '\0' reverse_int64( update_index )
```

--------------------------------

### Create and Tag a JGit Release

Source: https://github.com/eclipse-jgit/jgit/blob/master/tools/maven-central/README.md

Use the `tools/release.sh` script to create a new release version, update version identifiers in pom.xml and OSGi manifests, and create a signed, annotated tag.

```bash
./tools/release.sh v6.1.0.202203080745-r
```

--------------------------------

### Verify JGit Build

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Check your JGit build by running the 'version' command. This confirms the CLI is built and executable.

```bash
prompt$ ./jgit version
jgit version 0.10.0-SNAPSHOT
```

--------------------------------

### Test Staged Release with Maven

Source: https://github.com/eclipse-jgit/jgit/blob/master/tools/maven-central/README.md

Builds the jgit-build-test project using a Maven profile (-Pcentral.manual.testing) to verify that artifacts of the new JGit release can be downloaded and used.

```bash
mvn clean install -Pcentral.manual.testing
```

--------------------------------

### Configure Reftable Storage

Source: https://github.com/eclipse-jgit/jgit/blob/master/Documentation/technical/reftable.md

To enable reftable storage, the repository's configuration file must be updated to specify the repository format version and the refStorage extension.

```ini
[core]
	repositoryformatversion = 1
[extensions]
	refStorage = reftable
```

--------------------------------

### Create Symbolic Link for JGit

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Ease frequent JGit usage by creating a symbolic link to the binary, typically in a directory like /usr/local/bin.

```bash
sudo ln -s /path/to/jgit /usr/local/bin/jgit
```

--------------------------------

### List All JGit Debug Commands

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Display all available debug and test commands for JGit by running the 'debug-show-commands' command.

```bash
prompt$ ./jgit debug-show-commands
```

--------------------------------

### Build a JGit Repository

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Use FileRepositoryBuilder to construct a Repository object. It can scan the environment and file system for the Git directory.

```java
FileRepositoryBuilder builder = new FileRepositoryBuilder();
Repository repository = builder.setGitDir(new File("/my/git/directory"))
  .readEnvironment() // scan environment GIT_* variables
  .findGitDir() // scan up the file system tree
  .build();
```

--------------------------------

### Initialize SoftHSM Token

Source: https://github.com/eclipse-jgit/jgit/blob/master/org.eclipse.jgit.ssh.apache/manual_tests.txt

Initializes a new SoftHSM token with a specified slot, label, PIN, and SO-PIN. This is a prerequisite for importing keys and certificates.

```bash
$ softhsm2-util --init-token --slot 0 --label "TestToken" --pin 1234 --so-pin 4567
```

--------------------------------

### Commit Changes using Porcelain API

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Use the CommitCommand to perform a commit. You can set the commit message and other options. Ensure a Git instance is initialized with a Repository.

```java
Git git = new Git(db);
CommitCommand commit = git.commit();
commit.setMessage("initial commit").call();
```

--------------------------------

### Configure PKCS#11 SSH Provider

Source: https://github.com/eclipse-jgit/jgit/blob/master/org.eclipse.jgit.ssh.apache/README.md

Specify the path to the PKCS#11 shared library in `~/.ssh/config` to enable SSH authentication using a hardware security module.

```properties
PCKS11Provider /absolute/path/to/vendor/library.so
```

--------------------------------

### Download JGit Release and Create Signatures

Source: https://github.com/eclipse-jgit/jgit/blob/master/tools/maven-central/README.md

Downloads a specified JGit release from repo.eclipse.org and generates artifact signature files (.asc) using your GPG signing key.

```bash
pipenv run ./download_release.py 6.1.0.202203080745-r
```

--------------------------------

### Create RSA Key and Certificate

Source: https://github.com/eclipse-jgit/jgit/blob/master/org.eclipse.jgit.ssh.apache/manual_tests.txt

Generates a new RSA 4096-bit key pair and a self-signed certificate using OpenSSL. The key is output to key.pem and the certificate to cert.pem.

```bash
$ openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -subj "/CN=MyCertTEST" -nodes
```

--------------------------------

### Restrict Permissions for Configuration Files

Source: https://github.com/eclipse-jgit/jgit/blob/master/tools/maven-central/README.md

Secure your JReleaser configuration and GPG passphrase files by restricting read access to yourself. This is crucial for protecting sensitive credentials.

```bash
chmod 600 ~/.jreleaser/config.toml
chmod 600 ~/.gnupg/passphrase
```

--------------------------------

### Import RSA Key Pair into SoftHSM

Source: https://github.com/eclipse-jgit/jgit/blob/master/org.eclipse.jgit.ssh.apache/manual_tests.txt

Imports the generated RSA private key (key.pem) into the SoftHSM token. Requires the slot ID, a label for the key, an ID, and the token PIN.

```bash
$ softhsm2-util --import key.pem --slot 2006661923 --label "testkey" --id 1212 --pin 1234
```

--------------------------------

### Configure PKCS#11 Slot Index

Source: https://github.com/eclipse-jgit/jgit/blob/master/org.eclipse.jgit.ssh.apache/README.md

Set the `PKCS11SlotListIndex` in `~/.ssh/config` to select a specific PKCS#11 token if multiple are available. It is recommended to also include `IgnoreUnknown PKCS11SlotListIndex` to prevent OpenSSH errors.

```properties
IgnoreUnknown PKCS11SlotListIndex
```

--------------------------------

### Initialize RevWalk

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Initialize a RevWalk instance to walk a commit graph. This is used for parsing commits, tags, and trees.

```java
RevWalk walk = new RevWalk(repository);
```

--------------------------------

### Enable JGit Performance Tracing

Source: https://github.com/eclipse-jgit/jgit/blob/master/Documentation/config-options.md

Set the GIT_TRACE_PERFORMANCE system property to true to trace timings from the progress monitor. This can be done via environment variable or programmatically.

```bash
$ GIT_TRACE_PERFORMANCE=true jgit clone https://foo.bar/foobar
Cloning into 'foobar'...
remote: Counting objects: 1 [0.002s]
remote: Finding sources: 100% (15531/15531) [0.006s]
Receiving objects:      100% (169737/169737) [13.045s]
Resolving deltas:       100% (67579/67579) [1.842s]
```

--------------------------------

### Configure JReleaser Credentials for Maven Central

Source: https://github.com/eclipse-jgit/jgit/blob/master/tools/maven-central/README.md

Add your Maven Central username and token to the JReleaser configuration file. Ensure these files have restricted read access.

```toml
JRELEASER_GITHUB_TOKEN="EMPTY"
JRELEASER_MAVENCENTRAL_TOKEN="maven central token"
JRELEASER_MAVENCENTRAL_USERNAME="maven central username"
```

--------------------------------

### Reverse 64-bit Integer Function

Source: https://github.com/eclipse-jgit/jgit/blob/master/Documentation/technical/reftable.md

Provides the implementation for the reverse_int64 function, used to invert a 64-bit integer value for lexicographical sorting of log records.

```text
reverse_int64(int64 t) {
  return 0xffffffffffffffff - t;
}
```

--------------------------------

### Import Certificate into SoftHSM

Source: https://github.com/eclipse-jgit/jgit/blob/master/org.eclipse.jgit.ssh.apache/manual_tests.txt

Converts an X.509 certificate from PEM to DER format and then imports it into the SoftHSM token using pkcs11-tool. Requires the PKCS11 module path, object ID, label, and PIN.

```bash
$ openssl x509 -in cert.pem -out cert.der -outform DER
$ pkcs11-tool --module /opt/local/lib/softhsm/libsofthsm2.so -l --id 1212 --label "testcert" -y cert -w cert.der --pin 1234
```

--------------------------------

### Pushing Changes for Review

Source: https://github.com/eclipse-jgit/jgit/blob/master/CONTRIBUTING.md

Use this command to push your local commit to GerritHub for review. Ensure 'username' is replaced with your GitHub username.

```bash
git push ssh://username@eclipse.gerrithub.io:29418/eclipse-jgit/jgit HEAD:refs/for/master
```

--------------------------------

### Inspect Git Index with JGit CLI Tool

Source: https://github.com/eclipse-jgit/jgit/wiki/FAQ

Utilize the `jgit-cli.jar`'s `debug-show-dircache` command for a more detailed view of the Git index. This output includes mode, length, timestamp, object hash, and filename.

```bash
$ java -jar jgit-cli.jar --git-dir /c/git/jgit/.git debug-show-dircache
<mode><length>   <timestamp>         <object>                                      <file>
100644    871 20100706,131532.000    dc701694e405702940dc97caada20a3e5d64bbba      .eclipse_iplog
100644     17 20100219,165448.000    f57840b7eec86b91b135afc40f20d950c5d86988      .gitattributes
100644   1716 20100706,131532.000    1b85c64665f461a1ac948345c5f8034b751eda93      LICENSE
```

--------------------------------

### Varint Decoding Logic

Source: https://github.com/eclipse-jgit/jgit/blob/master/Documentation/technical/reftable.md

Illustrates the logic for decoding varint encoded values from a buffer, commonly used in pack files and reftables.

```java
val = buf[ptr] & 0x7f
    while (buf[ptr] & 0x80) {
      ptr++
      val = ((val + 1) << 7) | (buf[ptr] & 0x7f)
    }
```

--------------------------------

### Log Record Types

Source: https://github.com/eclipse-jgit/jgit/blob/master/Documentation/technical/reftable.md

Enumerates the different types of log records, specifically '0x0' for deletions and '0x1' for standard git reflog data.

```text
0x0: deletion; no log data.
0x1: standard git reflog data using `log_data` above.
```

--------------------------------

### Tag a Commit using Porcelain API

Source: https://github.com/eclipse-jgit/jgit/wiki/User-Guide

Use the TagCommand to create a tag for a specific commit. You can set the tag name, message, and other properties. Ensure a Git instance is initialized with a Repository.

```java
Git git = new Git(db);
RevCommit commit = git.commit().setMessage("initial commit").call();
RevTag tag = git.tag().setName("tag").call();
```

--------------------------------

### Inspect Git Index with Git CLI

Source: https://github.com/eclipse-jgit/jgit/wiki/FAQ

Use the `git ls-files -v -s` command to view the contents of the Git index. This shows file type, mode, object hash, stage, and filename.

```bash
$ git ls-files -v -s]
<file type> <mode> <object>                       <stage> <file>)
H 100644 dc701694e405702940dc97caada20a3e5d64bbba 0     .eclipse_iplog
H 100644 f57840b7eec86b91b135afc40f20d950c5d86988 0     .gitattributes
H 100644 1b85c64665f461a1ac948345c5f8034b751eda93 0     LICENSE
```

--------------------------------

### Configure SSH for PKCS11 Provider

Source: https://github.com/eclipse-jgit/jgit/blob/master/org.eclipse.jgit.ssh.apache/manual_tests.txt

Configures the ~/.ssh/config file to use a SoftHSM library as a PKCS11 provider for a specific host. This enables SSH connections to use keys managed by the PKCS11 token.

```bash
Host gitserver
Hostname git.eclipse.org
Port 29418
User ...
PKCS11Provider /opt/local/lib/softhsm/libsofthsm2.so
```