JGIT operations - get number of changes for a given file / published by https://github.com/dacr/code-examples-manager #7046d4fd-21ea-49d5-83b3-16220e5ce666/6e641e15988ad2d306310dc3c6a8a9355c3ee394

git-api-dealing-with-local-repo.sc

// summary : JGIT operations - get number of changes for a given file
// keywords : scala, git, @testable
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : 7046d4fd-21ea-49d5-83b3-16220e5ce666
// created-on : 2021-12-29T09:25:28.859219997Z
// managed-by : https://github.com/dacr/code-examples-manager
// run-with : scala-cli $file

// ---------------------
//> using scala  "3.1.1"
//> using dep "org.eclipse.jgit:org.eclipse.jgit:6.0.0.202111291000-r"
//> using dep "commons-io:commons-io:2.11.0"
//> using dep "org.slf4j:slf4j-nop:1.7.32"
// ---------------------

import java.io.File
import java.nio.file.{Files, Path}
import java.time.{Duration, Instant}
import scala.jdk.CollectionConverters.*
import scala.util.Properties
import org.eclipse.jgit.storage.file.FileRepositoryBuilder
import org.eclipse.jgit.api.Git
import org.eclipse.jgit.lib.Repository
import org.eclipse.jgit.lib.Constants
import org.eclipse.jgit.revwalk.RevCommit

val targetFilePath = Path.of("git-api-dealing-with-local-repo.sc").toAbsolutePath

def getLocalRepositoryFromFile(fromFile: File, ceilingDirectoryOption: Option[File] = None): Option[Repository] =
  val builder = new FileRepositoryBuilder()
  builder.setMustExist(true)
  ceilingDirectoryOption.foreach(ceilingDirectory => builder.addCeilingDirectory(ceilingDirectory))
  builder.findGitDir(fromFile)
  Option(builder.getGitDir()).map(_ => builder.build())

def getFileLog(git: Git, file: File, revision: String = Constants.HEAD): List[RevCommit] =
  val repository     = git.getRepository
  val repoHomeDir    = repository.getDirectory.toPath.getParent
  val revisionId     = repository.resolve(Constants.HEAD)
  val targetFile     = repoHomeDir.relativize(file.toPath)
  val targetFileLogs = git.log().add(revisionId).addPath(targetFile.toString).call()
  targetFileLogs.asScala.toList

def commitTimeInstant(revCommit: RevCommit): Instant =
  Instant.ofEpochSecond(revCommit.getCommitTime)

case class GitMetaData(changesCount: Int, createdOn: Instant, lastUpdated: Instant)

def getGitFileMetaData(git: Git, filePath: Path): Option[GitMetaData] =
  val targetFileLogs = getFileLog(git, filePath.toFile)
  val changesCount   = targetFileLogs.size
  for {
    createdOn   <- targetFileLogs.lastOption.map(commitTimeInstant)
    lastUpdated <- targetFileLogs.headOption.map(commitTimeInstant)
  } yield {
    GitMetaData(changesCount = changesCount, createdOn = createdOn, lastUpdated = lastUpdated)
  }

def getGitFileMetaData(filePath: Path): Option[GitMetaData] =
  for {
    homeFile <- Properties.envOrNone("HOME").map(new File(_)).filter(_.exists())
    fromFile <- Option(filePath).map(_.toFile).filter(_.exists())
    repo     <- getLocalRepositoryFromFile(fromFile, Some(homeFile))
    git       = Git(repo)  // TODO add close() call
    metadata <- getGitFileMetaData(git, filePath)
  } yield metadata


for {
  gitMetaData <- getGitFileMetaData(targetFilePath)
} {
  import gitMetaData.*
  println(
    s"""$targetFilePath
       |  $changesCount changes
       |  added on $createdOn
       |  last updated on $lastUpdated
       |  """.stripMargin
  )
}