diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 6da079b4..eaa64d59 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -6,11 +6,9 @@ on:
 jobs:
   ci:
     runs-on: ubuntu-latest
-    env:
-      GRADLE_OPTS: -Dorg.gradle.java.installations.fromEnv=JAVA_HOME_11_x64,JAVA_HOME_17_x64
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
@@ -20,6 +18,7 @@ jobs:
           distribution: temurin
           java-version: |
             11
+            21
             17
 
       - name: Validate Gradle Wrapper
diff --git a/.github/workflows/release.yaml b/.github/workflows/release.yaml
index 8c1786b7..06c176c2 100644
--- a/.github/workflows/release.yaml
+++ b/.github/workflows/release.yaml
@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
@@ -17,6 +17,7 @@ jobs:
           distribution: temurin
           java-version: |
             11
+            21
             17
 
       - name: Setup Gradle
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
index 41d9927a..7f93135c 100644
Binary files a/gradle/wrapper/gradle-wrapper.jar and b/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index ae04661e..9e33c2f3 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 distributionUrl=https\://services.gradle.org/distributions/gradle-7.5.1-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
index 1b6c7873..1aa94a42 100755
--- a/gradlew
+++ b/gradlew
@@ -55,7 +55,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.
@@ -80,13 +80,11 @@ do
     esac
 done
 
-APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
-
-APP_NAME="Gradle"
+# This is normally unused
+# shellcheck disable=SC2034
 APP_BASE_NAME=${0##*/}
-
-# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD=maximum
@@ -133,22 +131,29 @@ location of your Java installation."
     fi
 else
     JAVACMD=java
-    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
+    fi
 fi
 
 # Increase the maximum file descriptors if we can.
 if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
     case $MAX_FD in #(
       max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
         MAX_FD=$( ulimit -H -n ) ||
             warn "Could not query maximum file descriptor limit"
     esac
     case $MAX_FD in  #(
       '' | soft) :;; #(
       *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
         ulimit -n "$MAX_FD" ||
             warn "Could not set maximum file descriptor limit to $MAX_FD"
     esac
@@ -193,11 +198,15 @@ if "$cygwin" || "$msys" ; then
     done
 fi
 
-# Collect all arguments for the java command;
-#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
-#     shell script including quotes and variable substitutions, so put them in
-#     double quotes to make sure that they get re-expanded; and
-#   * put everything else in single quotes, so that it's not re-expanded.
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
@@ -205,6 +214,12 @@ set -- \
         org.gradle.wrapper.GradleWrapperMain \
         "$@"
 
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
 # Use "xargs" to parse quoted args.
 #
 # With -n1 it outputs one arg per line, with the quotes and backslashes removed.
diff --git a/gradlew.bat b/gradlew.bat
index ac1b06f9..6689b85b 100644
--- a/gradlew.bat
+++ b/gradlew.bat
@@ -14,7 +14,7 @@
 @rem limitations under the License.
 @rem
 
-@if "%DEBUG%" == "" @echo off
+@if "%DEBUG%"=="" @echo off
 @rem ##########################################################################
 @rem
 @rem  Gradle startup script for Windows
@@ -25,7 +25,8 @@
 if "%OS%"=="Windows_NT" setlocal
 
 set DIRNAME=%~dp0
-if "%DIRNAME%" == "" set DIRNAME=.
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
@@ -40,7 +41,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto execute
+if %ERRORLEVEL% equ 0 goto execute
 
 echo.
 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
@@ -75,13 +76,15 @@ set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
 :end
 @rem End local scope for the variables with windows NT shell
-if "%ERRORLEVEL%"=="0" goto mainEnd
+if %ERRORLEVEL% equ 0 goto mainEnd
 
 :fail
 rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
 rem the _cmd.exe /c_ return code!
-if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
-exit /b 1
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
 
 :mainEnd
 if "%OS%"=="Windows_NT" endlocal
diff --git a/grgit-core/gradle.lockfile b/grgit-core/gradle.lockfile
index a6563203..0d7026e4 100644
--- a/grgit-core/gradle.lockfile
+++ b/grgit-core/gradle.lockfile
@@ -1,19 +1,20 @@
 # This is a Gradle generated file for dependency locking.
 # Manual edits can break the build and are not advised.
 # This file is expected to be part of source control.
-com.googlecode.javaewah:JavaEWAH:1.1.13=compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
+com.googlecode.javaewah:JavaEWAH:1.2.3=compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
+commons-codec:commons-codec:1.16.0=compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
 org.apiguardian:apiguardian-api:1.1.2=testCompileClasspath
 org.codehaus.groovy:groovy:3.0.12=testCompileClasspath,testRuntimeClasspath
-org.codehaus.groovy:groovy:3.0.17=compileClasspath,default,runtimeClasspath
-org.eclipse.jgit:org.eclipse.jgit:6.5.0.202303070854-r=compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
+org.codehaus.groovy:groovy:3.0.19=compileClasspath,default,runtimeClasspath
+org.eclipse.jgit:org.eclipse.jgit:6.7.0.202309050840-r=compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
 org.hamcrest:hamcrest:2.2=testCompileClasspath,testRuntimeClasspath
-org.junit.jupiter:junit-jupiter-api:5.9.2=testCompileClasspath,testRuntimeClasspath
-org.junit.platform:junit-platform-commons:1.9.2=testCompileClasspath,testRuntimeClasspath
-org.junit.platform:junit-platform-engine:1.9.2=testCompileClasspath,testRuntimeClasspath
-org.junit:junit-bom:5.9.2=testCompileClasspath,testRuntimeClasspath
-org.opentest4j:opentest4j:1.2.0=testCompileClasspath,testRuntimeClasspath
-org.slf4j:slf4j-api:1.7.30=compileClasspath,default,runtimeClasspath
-org.slf4j:slf4j-api:2.0.7=testCompileClasspath,testRuntimeClasspath
-org.slf4j:slf4j-simple:2.0.7=testRuntimeClasspath
+org.junit.jupiter:junit-jupiter-api:5.10.0=testCompileClasspath,testRuntimeClasspath
+org.junit.platform:junit-platform-commons:1.10.0=testCompileClasspath,testRuntimeClasspath
+org.junit.platform:junit-platform-engine:1.10.0=testCompileClasspath,testRuntimeClasspath
+org.junit:junit-bom:5.10.0=testCompileClasspath,testRuntimeClasspath
+org.opentest4j:opentest4j:1.3.0=testCompileClasspath,testRuntimeClasspath
+org.slf4j:slf4j-api:1.7.36=compileClasspath,default,runtimeClasspath
+org.slf4j:slf4j-api:2.0.9=testCompileClasspath,testRuntimeClasspath
+org.slf4j:slf4j-simple:2.0.9=testRuntimeClasspath
 org.spockframework:spock-core:2.3-groovy-3.0=testCompileClasspath,testRuntimeClasspath
 empty=annotationProcessor,archives,signatures,testAnnotationProcessor
diff --git a/grgit-gradle/build.gradle.kts b/grgit-gradle/build.gradle.kts
index 3594b8d8..76113efd 100644
--- a/grgit-gradle/build.gradle.kts
+++ b/grgit-gradle/build.gradle.kts
@@ -57,6 +57,14 @@ stutter {
       compatibleRange("7.3")
     }
   }
+  val java21 by matrices.creating {
+    javaToolchain {
+      languageVersion.set(JavaLanguageVersion.of(21))
+    }
+    gradleVersions {
+      compatibleRange("8.4")
+    }
+  }
 }
 
 tasks.named("check") {
diff --git a/grgit-gradle/gradle.lockfile b/grgit-gradle/gradle.lockfile
index 3cbb5efa..06ebc891 100644
--- a/grgit-gradle/gradle.lockfile
+++ b/grgit-gradle/gradle.lockfile
@@ -1,15 +1,16 @@
 # This is a Gradle generated file for dependency locking.
 # Manual edits can break the build and are not advised.
 # This file is expected to be part of source control.
-com.googlecode.javaewah:JavaEWAH:1.1.13=compatTestCompileClasspath,compatTestRuntimeClasspath,compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
+com.googlecode.javaewah:JavaEWAH:1.2.3=compatTestCompileClasspath,compatTestRuntimeClasspath,compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
+commons-codec:commons-codec:1.16.0=compatTestCompileClasspath,compatTestRuntimeClasspath,compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
 org.apiguardian:apiguardian-api:1.1.2=compatTestCompileClasspath
 org.codehaus.groovy:groovy:3.0.12=compatTestCompileClasspath,compatTestRuntimeClasspath
-org.eclipse.jgit:org.eclipse.jgit:6.5.0.202303070854-r=compatTestCompileClasspath,compatTestRuntimeClasspath,compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
+org.eclipse.jgit:org.eclipse.jgit:6.7.0.202309050840-r=compatTestCompileClasspath,compatTestRuntimeClasspath,compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
 org.hamcrest:hamcrest:2.2=compatTestCompileClasspath,compatTestRuntimeClasspath
 org.junit.platform:junit-platform-commons:1.9.0=compatTestCompileClasspath,compatTestRuntimeClasspath
 org.junit.platform:junit-platform-engine:1.9.0=compatTestCompileClasspath,compatTestRuntimeClasspath
 org.junit:junit-bom:5.9.0=compatTestCompileClasspath,compatTestRuntimeClasspath
 org.opentest4j:opentest4j:1.2.0=compatTestCompileClasspath,compatTestRuntimeClasspath
-org.slf4j:slf4j-api:1.7.30=compatTestCompileClasspath,compatTestRuntimeClasspath,compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
+org.slf4j:slf4j-api:1.7.36=compatTestCompileClasspath,compatTestRuntimeClasspath,compileClasspath,default,runtimeClasspath,testCompileClasspath,testRuntimeClasspath
 org.spockframework:spock-core:2.3-groovy-3.0=compatTestCompileClasspath,compatTestRuntimeClasspath
 empty=annotationProcessor,archives,compatTestAnnotationProcessor,signatures,testAnnotationProcessor
diff --git a/grgit-gradle/stutter.lockfile b/grgit-gradle/stutter.lockfile
index 7f708003..6989ea6a 100644
--- a/grgit-gradle/stutter.lockfile
+++ b/grgit-gradle/stutter.lockfile
@@ -1,3 +1,4 @@
 # DO NOT MODIFY: Generated by Stutter plugin.
-java11=7.0.2,7.6.1,8.0.2,8.1.1
-java17=7.3.3,7.6.1,8.0.2,8.1.1
+java11=7.0.2,7.6.3,8.0.2,8.4
+java17=7.3.3,7.6.3,8.0.2,8.4
+java21=8.4
diff --git a/settings.gradle.kts b/settings.gradle.kts
index a42abbc7..1dc5d42e 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -6,7 +6,7 @@ pluginManagement {
     id("org.ajoberstar.reckon.settings") version "0.18.0"
     id("org.ajoberstar.stutter") version "0.7.2"
 
-    id("com.diffplug.spotless") version "6.18.0"
+    id("com.diffplug.spotless") version "6.22.0"
   }
 
   repositories {