build: work around gpg pin-entry issue

Author: ctron

pom.xml

@@ -88,7 +88,6 @@
         <maven-compiler-plugin.version>3.10.1</maven-compiler-plugin.version>
         <maven-deploy-plugin.version>3.0.0-M2</maven-deploy-plugin.version>
         <maven-enforcer-plugin.version>3.1.0</maven-enforcer-plugin.version>
-        <maven-gpg-plugin.version>3.0.1</maven-gpg-plugin.version>
         <maven-install-plugin.version>3.0.0-M1</maven-install-plugin.version>
         <maven-jar-plugin.version>3.2.2</maven-jar-plugin.version>
         <maven-javadoc-plugin.version>3.4.0</maven-javadoc-plugin.version>
@@ -99,6 +98,21 @@
         <maven-source-plugin.version>3.2.1</maven-source-plugin.version>
         <maven-surefire-plugin.version>3.0.0-M7</maven-surefire-plugin.version>
         <spotless-maven-plugin.version>2.4.1</spotless-maven-plugin.version>
+
+        <!--
+        downgrade to 1.6 to fix gpg signing issue with pinentry:
+
+        gpg signing might require a pin-entry. The gpg plugin expects a pin provided through maven settings. If none is
+        present, but required, a dialog will pop up. Starting with version 3.0.1, this will be prevented (with an error)
+        in case the maven is running in non-interactive mode.
+
+        All good, however if you have a USB stick to sign, you might expect/want/require a manual pin entry, and not
+        write down your pin in a config file. Unfortunately, the maven release plugin runs the gpg sign plugin always
+        in non-interactive mode.
+
+        Downgrading to 1.6 fixes this issue, as the pin-entry is not forced to "error".
+        -->
+        <maven-gpg-plugin.version>1.6</maven-gpg-plugin.version>
     </properties>
 
     <dependencyManagement>