Merge branch 'stable-5.1' into stable-5.2

* stable-5.1:
  Update maven plugins
  Ignore missing javadoc in test bundles
  storage: file: De-duplicate File.exists()+File.isFile()
  RefDirectory.scanRef: Re-use file existence check done in snapshot creation
  FileSnapshot: Lazy load file store attributes cache
  Update eclipse-jarsigner-plugin to 1.3.2
  Fix p2 repository URLs

Change-Id: If3ad2cfb6c341b0ff5c2120a5a1646f6368d86e7

20 files changed, 78 insertions, 52 deletions

diff --git a/org.eclipse.jgit.ant.test/.settings/org.eclipse.jdt.core.prefs b/org.eclipse.jgit.ant.test/.settings/org.eclipse.jdt.core.prefs
index 2ca78ff2d0..d4751b5352 100644
--- a/org.eclipse.jgit.ant.test/.settings/org.eclipse.jdt.core.prefs
+++ b/org.eclipse.jgit.ant.test/.settings/org.eclipse.jdt.core.prefs
@@ -52,7 +52,7 @@ org.eclipse.jdt.core.compiler.problem.missingJavadocComments=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsVisibility=protected
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagDescription=return_tag
-org.eclipse.jdt.core.compiler.problem.missingJavadocTags=error
+org.eclipse.jdt.core.compiler.problem.missingJavadocTags=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsMethodTypeParameters=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsVisibility=private
diff --git a/org.eclipse.jgit.http.test/.settings/org.eclipse.jdt.core.prefs b/org.eclipse.jgit.http.test/.settings/org.eclipse.jdt.core.prefs
index 2ca78ff2d0..d4751b5352 100644
--- a/org.eclipse.jgit.http.test/.settings/org.eclipse.jdt.core.prefs
+++ b/org.eclipse.jgit.http.test/.settings/org.eclipse.jdt.core.prefs
@@ -52,7 +52,7 @@ org.eclipse.jdt.core.compiler.problem.missingJavadocComments=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsVisibility=protected
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagDescription=return_tag
-org.eclipse.jdt.core.compiler.problem.missingJavadocTags=error
+org.eclipse.jdt.core.compiler.problem.missingJavadocTags=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsMethodTypeParameters=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsVisibility=private
diff --git a/org.eclipse.jgit.lfs.server.test/.settings/org.eclipse.jdt.core.prefs b/org.eclipse.jgit.lfs.server.test/.settings/org.eclipse.jdt.core.prefs
index 2ca78ff2d0..d4751b5352 100644
--- a/org.eclipse.jgit.lfs.server.test/.settings/org.eclipse.jdt.core.prefs
+++ b/org.eclipse.jgit.lfs.server.test/.settings/org.eclipse.jdt.core.prefs
@@ -52,7 +52,7 @@ org.eclipse.jdt.core.compiler.problem.missingJavadocComments=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsVisibility=protected
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagDescription=return_tag
-org.eclipse.jdt.core.compiler.problem.missingJavadocTags=error
+org.eclipse.jdt.core.compiler.problem.missingJavadocTags=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsMethodTypeParameters=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsVisibility=private
diff --git a/org.eclipse.jgit.lfs.test/.settings/org.eclipse.jdt.core.prefs b/org.eclipse.jgit.lfs.test/.settings/org.eclipse.jdt.core.prefs
index 2ca78ff2d0..d4751b5352 100644
--- a/org.eclipse.jgit.lfs.test/.settings/org.eclipse.jdt.core.prefs
+++ b/org.eclipse.jgit.lfs.test/.settings/org.eclipse.jdt.core.prefs
@@ -52,7 +52,7 @@ org.eclipse.jdt.core.compiler.problem.missingJavadocComments=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsVisibility=protected
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagDescription=return_tag
-org.eclipse.jdt.core.compiler.problem.missingJavadocTags=error
+org.eclipse.jdt.core.compiler.problem.missingJavadocTags=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsMethodTypeParameters=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsVisibility=private
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.10-staging.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.10.target
index 55e44b8f7b..268fbc7575 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.10-staging.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.10.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.9-staging" sequenceNumber="1566229361">
+<target name="jgit-4.9-staging" sequenceNumber="1638575042">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.jetty.client" version="9.4.11.v20180605"/>
@@ -20,7 +20,7 @@
       <unit id="org.eclipse.jetty.servlet.source" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util.source" version="9.4.11.v20180605"/>
-      <repository id="jetty-9.4.11" location="http://download.eclipse.org/jetty/updates/jetty-bundles-9.x/9.4.11.v20180605"/>
+      <repository id="jetty-9.4.11" location="https://archive.eclipse.org/jetty/updates/jetty-bundles-9.x/jetty-bundles-9.x/9.4.11.v20180605/"/>
     </location>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.apache.ant" version="1.10.5.v20190526-1402"/>
@@ -80,7 +80,7 @@
     </location>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.osgi" version="0.0.0"/>
-      <repository location="http://download.eclipse.org/staging/2018-12/"/>
+      <repository location="http://download.eclipse.org/releases/2018-12/"/>
     </location>
   </locations>
 </target>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.10-staging.tpd b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.10.tpd
index 98bbc2d8ca..71230d705e 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.10-staging.tpd
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.10.tpd
@@ -3,6 +3,6 @@ target "jgit-4.9-staging" with source configurePhase
 include "projects/jetty-9.4.11.tpd"
 include "orbit/R20190602212107-2019-06.tpd"
 
-location "http://download.eclipse.org/staging/2018-12/" {
+location "http://download.eclipse.org/releases/2018-12/" {
 	org.eclipse.osgi lazy
 }
\ No newline at end of file
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.5.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.5.target
index 7820a13581..15ee446805 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.5.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.5.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.5" sequenceNumber="1566229356">
+<target name="jgit-4.5" sequenceNumber="1638575045">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.jetty.client" version="9.4.11.v20180605"/>
@@ -20,7 +20,7 @@
       <unit id="org.eclipse.jetty.servlet.source" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util.source" version="9.4.11.v20180605"/>
-      <repository id="jetty-9.4.11" location="http://download.eclipse.org/jetty/updates/jetty-bundles-9.x/9.4.11.v20180605"/>
+      <repository id="jetty-9.4.11" location="https://archive.eclipse.org/jetty/updates/jetty-bundles-9.x/jetty-bundles-9.x/9.4.11.v20180605/"/>
     </location>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.apache.ant" version="1.10.5.v20190526-1402"/>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.6.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.6.target
index 997d9c9832..bc1c54f52e 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.6.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.6.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.6" sequenceNumber="1566229352">
+<target name="jgit-4.6" sequenceNumber="1638575051">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.jetty.client" version="9.4.11.v20180605"/>
@@ -20,7 +20,7 @@
       <unit id="org.eclipse.jetty.servlet.source" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util.source" version="9.4.11.v20180605"/>
-      <repository id="jetty-9.4.11" location="http://download.eclipse.org/jetty/updates/jetty-bundles-9.x/9.4.11.v20180605"/>
+      <repository id="jetty-9.4.11" location="https://archive.eclipse.org/jetty/updates/jetty-bundles-9.x/jetty-bundles-9.x/9.4.11.v20180605/"/>
     </location>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.apache.ant" version="1.10.5.v20190526-1402"/>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.7.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.7.target
index 03c9a8b528..596e3c4d04 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.7.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.7.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.7" sequenceNumber="1566229348">
+<target name="jgit-4.7" sequenceNumber="1638575047">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.jetty.client" version="9.4.11.v20180605"/>
@@ -20,7 +20,7 @@
       <unit id="org.eclipse.jetty.servlet.source" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util.source" version="9.4.11.v20180605"/>
-      <repository id="jetty-9.4.11" location="http://download.eclipse.org/jetty/updates/jetty-bundles-9.x/9.4.11.v20180605"/>
+      <repository id="jetty-9.4.11" location="https://archive.eclipse.org/jetty/updates/jetty-bundles-9.x/jetty-bundles-9.x/9.4.11.v20180605/"/>
     </location>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.apache.ant" version="1.10.5.v20190526-1402"/>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.8.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.8.target
index e29620cc11..a0e0948600 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.8.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.8.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.8" sequenceNumber="1566229344">
+<target name="jgit-4.8" sequenceNumber="1638575042">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.jetty.client" version="9.4.11.v20180605"/>
@@ -20,7 +20,7 @@
       <unit id="org.eclipse.jetty.servlet.source" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util.source" version="9.4.11.v20180605"/>
-      <repository id="jetty-9.4.11" location="http://download.eclipse.org/jetty/updates/jetty-bundles-9.x/9.4.11.v20180605"/>
+      <repository id="jetty-9.4.11" location="https://archive.eclipse.org/jetty/updates/jetty-bundles-9.x/jetty-bundles-9.x/9.4.11.v20180605/"/>
     </location>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.apache.ant" version="1.10.5.v20190526-1402"/>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.9.target b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.9.target
index 82a64ce3d5..a4dd92c88c 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.9.target
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.9.target
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
 <?pde?>
 <!-- generated with https://github.com/eclipse-cbi/targetplatform-dsl -->
-<target name="jgit-4.9" sequenceNumber="1566229339">
+<target name="jgit-4.9" sequenceNumber="1638575042">
   <locations>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.jetty.client" version="9.4.11.v20180605"/>
@@ -20,7 +20,7 @@
       <unit id="org.eclipse.jetty.servlet.source" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util" version="9.4.11.v20180605"/>
       <unit id="org.eclipse.jetty.util.source" version="9.4.11.v20180605"/>
-      <repository id="jetty-9.4.11" location="http://download.eclipse.org/jetty/updates/jetty-bundles-9.x/9.4.11.v20180605"/>
+      <repository id="jetty-9.4.11" location="https://archive.eclipse.org/jetty/updates/jetty-bundles-9.x/jetty-bundles-9.x/9.4.11.v20180605/"/>
     </location>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.apache.ant" version="1.10.5.v20190526-1402"/>
@@ -80,7 +80,7 @@
     </location>
     <location includeMode="slicer" includeAllPlatforms="false" includeSource="true" includeConfigurePhase="true" type="InstallableUnit">
       <unit id="org.eclipse.osgi" version="0.0.0"/>
-      <repository location="http://download.eclipse.org/releases/2018-09/"/>
+      <repository location="https://download.eclipse.org/releases/2018-09/"/>
     </location>
   </locations>
 </target>
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.9.tpd b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.9.tpd
index d5beea3616..6ee4c6a848 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.9.tpd
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/jgit-4.9.tpd
@@ -3,6 +3,6 @@ target "jgit-4.9" with source configurePhase
 include "projects/jetty-9.4.11.tpd"
 include "orbit/R20190602212107-2019-06.tpd"
 
-location "http://download.eclipse.org/releases/2018-09/" {
+location "https://download.eclipse.org/releases/2018-09/" {
 	org.eclipse.osgi lazy
 }
\ No newline at end of file
diff --git a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/projects/jetty-9.4.11.tpd b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/projects/jetty-9.4.11.tpd
index d2fd9017b3..4b4612147c 100644
--- a/org.eclipse.jgit.packaging/org.eclipse.jgit.target/projects/jetty-9.4.11.tpd
+++ b/org.eclipse.jgit.packaging/org.eclipse.jgit.target/projects/jetty-9.4.11.tpd
@@ -1,6 +1,6 @@
 target "jetty-9.4.11" with source configurePhase
 
-location jetty-9.4.11 "http://download.eclipse.org/jetty/updates/jetty-bundles-9.x/9.4.11.v20180605" {
+location jetty-9.4.11 "https://archive.eclipse.org/jetty/updates/jetty-bundles-9.x/jetty-bundles-9.x/9.4.11.v20180605/" {
 	org.eclipse.jetty.client [9.4.11.v20180605,9.4.11.v20180605]
 	org.eclipse.jetty.client.source [9.4.11.v20180605,9.4.11.v20180605]
 	org.eclipse.jetty.continuation [9.4.11.v20180605,9.4.11.v20180605]
diff --git a/org.eclipse.jgit.packaging/pom.xml b/org.eclipse.jgit.packaging/pom.xml
index d8d061e36e..35fa738c78 100644
--- a/org.eclipse.jgit.packaging/pom.xml
+++ b/org.eclipse.jgit.packaging/pom.xml
@@ -55,7 +55,7 @@
   <name>JGit Tycho Parent</name>
 
   <properties>
-    <tycho-version>1.3.0</tycho-version>
+    <tycho-version>1.7.0</tycho-version>
     <tycho-extras-version>${tycho-version}</tycho-extras-version>
     <target-platform>jgit-4.6</target-platform>
   </properties>
@@ -255,7 +255,7 @@
         <plugin>
           <groupId>org.eclipse.cbi.maven.plugins</groupId>
           <artifactId>eclipse-jarsigner-plugin</artifactId>
-          <version>1.1.5</version>
+          <version>1.3.2</version>
         </plugin>
         <plugin>
           <groupId>org.codehaus.mojo</groupId>
diff --git a/org.eclipse.jgit.pgm.test/.settings/org.eclipse.jdt.core.prefs b/org.eclipse.jgit.pgm.test/.settings/org.eclipse.jdt.core.prefs
index 2ca78ff2d0..d4751b5352 100644
--- a/org.eclipse.jgit.pgm.test/.settings/org.eclipse.jdt.core.prefs
+++ b/org.eclipse.jgit.pgm.test/.settings/org.eclipse.jdt.core.prefs
@@ -52,7 +52,7 @@ org.eclipse.jdt.core.compiler.problem.missingJavadocComments=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsVisibility=protected
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagDescription=return_tag
-org.eclipse.jdt.core.compiler.problem.missingJavadocTags=error
+org.eclipse.jdt.core.compiler.problem.missingJavadocTags=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsMethodTypeParameters=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsVisibility=private
diff --git a/org.eclipse.jgit.test/.settings/org.eclipse.jdt.core.prefs b/org.eclipse.jgit.test/.settings/org.eclipse.jdt.core.prefs
index 2ca78ff2d0..d4751b5352 100644
--- a/org.eclipse.jgit.test/.settings/org.eclipse.jdt.core.prefs
+++ b/org.eclipse.jgit.test/.settings/org.eclipse.jdt.core.prefs
@@ -52,7 +52,7 @@ org.eclipse.jdt.core.compiler.problem.missingJavadocComments=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocCommentsVisibility=protected
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagDescription=return_tag
-org.eclipse.jdt.core.compiler.problem.missingJavadocTags=error
+org.eclipse.jdt.core.compiler.problem.missingJavadocTags=ignore
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsMethodTypeParameters=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsOverriding=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsVisibility=private
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileSnapshot.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileSnapshot.java
index 976f946e5d..654e98d817 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileSnapshot.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileSnapshot.java
@@ -218,6 +218,12 @@ public class FileSnapshot {
 	private FileStoreAttributes fileStoreAttributeCache;
 
 	/**
+	 * if {@code true} read filesystem time resolution from configuration file
+	 * otherwise use fallback resolution
+	 */
+	private boolean useConfig;
+
+	/**
 	 * Object that uniquely identifies the given file, or {@code
 	 * null} if a file key is not available
 	 */
@@ -253,9 +259,7 @@ public class FileSnapshot {
 	protected FileSnapshot(File file, boolean useConfig) {
 		this.file = file;
 		this.lastRead = Instant.now();
-		this.fileStoreAttributeCache = useConfig
-				? FS.getFileStoreAttributes(file.toPath().getParent())
-				: FALLBACK_FILESTORE_ATTRIBUTES;
+		this.useConfig = useConfig;
 		BasicFileAttributes fileAttributes = null;
 		try {
 			fileAttributes = FS.DETECTED.fileAttributes(file);
@@ -399,7 +403,7 @@ public class FileSnapshot {
 	 *             if sleep was interrupted
 	 */
 	public void waitUntilNotRacy() throws InterruptedException {
-		long timestampResolution = fileStoreAttributeCache
+		long timestampResolution = fileStoreAttributeCache()
 				.getFsTimestampResolution().toNanos();
 		while (isRacyClean(Instant.now())) {
 			TimeUnit.NANOSECONDS.sleep(timestampResolution);
@@ -435,6 +439,15 @@ public class FileSnapshot {
 		return equals(other);
 	}
 
+	/**
+	 * Check if the file exists
+	 *
+	 * @return true if the file exists
+	 */
+	public boolean fileExists() {
+		return !MISSING_FILEKEY.equals(this.fileKey);
+	}
+
 	/** {@inheritDoc} */
 	@Override
 	public int hashCode() {
@@ -519,10 +532,10 @@ public class FileSnapshot {
 	}
 
 	private long getEffectiveRacyThreshold() {
-		long timestampResolution = fileStoreAttributeCache
+		long timestampResolution = fileStoreAttributeCache()
 				.getFsTimestampResolution().toNanos();
-		long minRacyInterval = fileStoreAttributeCache.getMinimalRacyInterval()
-				.toNanos();
+		long minRacyInterval = fileStoreAttributeCache()
+				.getMinimalRacyInterval().toNanos();
 		long max = Math.max(timestampResolution, minRacyInterval);
 		// safety margin: factor 2.5 below 100ms otherwise 1.25
 		return max < 100_000_000L ? max * 5 / 2 : max * 5 / 4;
@@ -582,4 +595,13 @@ public class FileSnapshot {
 		}
 		return changed;
 	}
+
+	private FileStoreAttributes fileStoreAttributeCache() {
+		if (fileStoreAttributeCache == null) {
+			fileStoreAttributeCache = useConfig
+					? FS.getFileStoreAttributes(file.toPath().getParent())
+					: FALLBACK_FILESTORE_ATTRIBUTES;
+		}
+		return fileStoreAttributeCache;
+	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectoryPackParser.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectoryPackParser.java
index 6e8a15e86d..889a5108d4 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectoryPackParser.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectoryPackParser.java
@@ -184,7 +184,7 @@ public class ObjectDirectoryPackParser extends PackParser {
 		String p = pack.getAbsolutePath();
 		String i = p.substring(0, p.length() - ".pack".length()) + ".idx"; //$NON-NLS-1$ //$NON-NLS-2$
 		File idx = new File(i);
-		if (idx.exists() && idx.isFile())
+		if (idx.isFile())
 			size += idx.length();
 		return size;
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
index f7a52a54b6..c34be9cc0a 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
@@ -1103,10 +1103,14 @@ public class RefDirectory extends RefDatabase {
 		final int limit = 4096;
 		final byte[] buf;
 		FileSnapshot otherSnapshot = FileSnapshot.save(path);
+		if (!otherSnapshot.fileExists()) {
+			return null;
+		}
+
 		try {
 			buf = IO.readSome(path, limit);
 		} catch (FileNotFoundException noFile) {
-			if (path.exists() && path.isFile()) {
+			if (path.isFile()) {
 				throw noFile;
 			}
 			return null; // doesn't exist or no file; not a reference.
diff --git a/pom.xml b/pom.xml
index b0fc1e738c..df604a6ed1 100644
--- a/pom.xml
+++ b/pom.xml
@@ -199,13 +199,13 @@
     <httpcore-version>4.4.10</httpcore-version>
     <slf4j-version>1.7.2</slf4j-version>
     <log4j-version>1.2.15</log4j-version>
-    <maven-javadoc-plugin-version>3.1.0</maven-javadoc-plugin-version>
-    <tycho-extras-version>1.3.0</tycho-extras-version>
+    <maven-javadoc-plugin-version>3.3.1</maven-javadoc-plugin-version>
+    <tycho-extras-version>1.7.0</tycho-extras-version>
     <gson-version>2.8.2</gson-version>
-    <maven-project-info-reports-plugin-version>3.0.0</maven-project-info-reports-plugin-version>
-    <maven-jxr-plugin-version>3.0.0</maven-jxr-plugin-version>
-    <spotbugs-maven-plugin-version>3.1.12</spotbugs-maven-plugin-version>
-    <maven-surefire-plugin-version>3.0.0-M3</maven-surefire-plugin-version>
+    <maven-project-info-reports-plugin-version>3.1.2</maven-project-info-reports-plugin-version>
+    <maven-jxr-plugin-version>3.1.1</maven-jxr-plugin-version>
+    <spotbugs-maven-plugin-version>4.3.0</spotbugs-maven-plugin-version>
+    <maven-surefire-plugin-version>3.0.0-M5</maven-surefire-plugin-version>
     <maven-surefire-report-plugin-version>${maven-surefire-plugin-version}</maven-surefire-report-plugin-version>
     <maven-compiler-plugin-version>3.8.1</maven-compiler-plugin-version>
 
@@ -239,7 +239,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-jar-plugin</artifactId>
-          <version>3.1.2</version>
+          <version>3.2.0</version>
           <configuration>
             <archive>
               <manifestEntries>
@@ -264,25 +264,25 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-shade-plugin</artifactId>
-          <version>3.2.1</version>
+          <version>3.2.4</version>
         </plugin>
 
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-antrun-plugin</artifactId>
-          <version>1.8</version>
+          <version>3.0.0</version>
         </plugin>
 
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-dependency-plugin</artifactId>
-          <version>3.1.1</version>
+          <version>3.2.0</version>
         </plugin>
 
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-source-plugin</artifactId>
-          <version>3.1.0</version>
+          <version>3.2.1</version>
         </plugin>
 
         <plugin>
@@ -304,7 +304,7 @@
         <plugin>
           <groupId>org.codehaus.mojo</groupId>
           <artifactId>build-helper-maven-plugin</artifactId>
-          <version>3.0.0</version>
+          <version>3.2.0</version>
         </plugin>
 
         <plugin>
@@ -327,7 +327,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-pmd-plugin</artifactId>
-          <version>3.12.0</version>
+          <version>3.15.0</version>
           <configuration>
             <sourceEncoding>utf-8</sourceEncoding>
             <minimumTokens>100</minimumTokens>
@@ -350,7 +350,7 @@
         <plugin>
           <groupId>org.eclipse.cbi.maven.plugins</groupId>
           <artifactId>eclipse-jarsigner-plugin</artifactId>
-          <version>1.1.5</version>
+          <version>1.3.2</version>
         </plugin>
         <plugin>
           <groupId>org.eclipse.tycho.extras</groupId>
@@ -365,12 +365,12 @@
         <plugin>
           <groupId>org.jacoco</groupId>
           <artifactId>jacoco-maven-plugin</artifactId>
-          <version>0.8.4</version>
+          <version>0.8.7</version>
         </plugin>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-site-plugin</artifactId>
-          <version>3.7.1</version>
+          <version>3.9.1</version>
           <dependencies>
             <dependency><!-- add support for ssh/scp -->
               <groupId>org.apache.maven.wagon</groupId>
@@ -412,7 +412,7 @@
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-resources-plugin</artifactId>
-          <version>3.1.0</version>
+          <version>3.2.0</version>
         </plugin>
       </plugins>
     </pluginManagement>
@@ -421,7 +421,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-enforcer-plugin</artifactId>
-        <version>3.0.0-M2</version>
+        <version>3.0.0</version>
         <executions>
           <execution>
             <id>enforce-maven</id>