Fix all Javadoc warnings and fail on them

This fixes all the javadoc warnings, stops ignoring doclint 'missing'
category and fails the build on javadoc warnings for public and
protected classes and class members.

Since javadoc doesn't allow access specifiers when specifying doclint
configuration we cannot set `-Xdoclint:all,-missing/private`
hence there is no simple way to skip private elements from doclint.
Therefore we check javadoc using the Eclipse Java compiler
(which is used by default) and javadoc configuration in
`.settings/org.eclipse.jdt.core.prefs` files.
This allows more fine grained configuration.

We can reconsider this when javadoc starts supporting access specifiers
in the doclint configuration.

Below are detailled explanations for most modifications.

@inheritDoc
===========
doclint complains about explicits `{@inheritDoc}` when the parent does
not have any documentation. As far as I can tell, javadoc defaults to
inherit comments and should only be used when one wants to append extra
documentation from the parent. Given the parent has no documentation,
remove those usages which doclint complains about.

In some case I have moved up the documentation from the concrete class
up to the abstract class.

Remove `{@inheritDoc}` on overriden methods which don't add additional
documentation since javadoc defaults to inherit javadoc of overridden
methods.

@value to @link
===============
In PackConfig, DEFAULT_SEARCH_FOR_REUSE_TIMEOUT and similar are forged
from Integer.MAX_VALUE and are thus not considered constants (I guess
cause the value would depends on the platform). Replace it with a link
to `Integer.MAX_VALUE`.

In `StringUtils.toBoolean`, @value was used to refer to the
`stringValue` parameter. I have replaced it with `{@code stringValue}`.

{@link <url>} to <a>
====================
@link does not support being given an external URL. Replaces them with
HTML `<a>`.

@since: being invalid
=====================

org.eclipse.jgit/src/org/eclipse/jgit/util/Equality.java has an invalid
tag `@since: ` due to the extra `:`. Javadoc does not complain about it
with version 11.0.18+10 but does with 11.0.19.7. It is invalid
regardless.

invalid HTML syntax
===================

- javadoc doesn't allow <br/>, <p/> and </p> anymore, use <br> and <p>
instead
- replace <tt>code</tt> by {@code code}
- <table> tags don't allow summary attribute, specify caption as
<caption>caption</caption> to fix this

doclint visibility issue
========================

In the private abstract classes `BaseDirCacheEditor` and
`BasePackConnection` links to other methods in the abstract class are
inherited in the public subclasses but doclint gets confused and
considers them unreachable. The HTML documentation for the sub classes
shows the relative links in the sub classes, so it is all correct. It
must be a bug somewhere in javadoc.
Mute those warnings with: @SuppressWarnings("doclint:missing")

Misc
====
Replace `<` and `>` with HTML encoded entities (`&lt; and `&gt;`).
In `SshConstants` I went enclosing a serie of -> arrows in @literal.

Additional tags
===============
Configure maven-javad0c-plugin to allow the following additional tags
defined in https://openjdk.org/jeps/8068562:
- apiNote
- implSpec
- implNote

Missing javadoc
===============
Add missing @params and descriptions

Change-Id: I840056389aa59135cfb360da0d5e40463ce35bd0
Also-By: Matthias Sohn <matthias.sohn@sap.com>

6 files changed, 20 insertions, 4 deletions

diff --git a/org.eclipse.jgit.gpg.bc/.settings/org.eclipse.jdt.core.prefs b/org.eclipse.jgit.gpg.bc/.settings/org.eclipse.jdt.core.prefs
index d1f54bbe65..d5c0e6c7e0 100644
--- a/org.eclipse.jgit.gpg.bc/.settings/org.eclipse.jdt.core.prefs
+++ b/org.eclipse.jgit.gpg.bc/.settings/org.eclipse.jdt.core.prefs
@@ -52,7 +52,7 @@ org.eclipse.jdt.core.compiler.problem.missingHashCodeMethod=error
 org.eclipse.jdt.core.compiler.problem.missingJavadocComments=error
 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.missingJavadocTagDescription=all_standard_tags
 org.eclipse.jdt.core.compiler.problem.missingJavadocTags=error
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsMethodTypeParameters=disabled
 org.eclipse.jdt.core.compiler.problem.missingJavadocTagsOverriding=disabled
diff --git a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgKeyLocator.java b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgKeyLocator.java
index 8cd03bd36f..d7bf34e3ac 100644
--- a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgKeyLocator.java
+++ b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgKeyLocator.java
@@ -324,7 +324,9 @@ public class BouncyCastleGpgKeyLocator {
 	 * @throws IOException
 	 *             in case of problems reading the file
 	 * @throws NoSuchAlgorithmException
+	 *             if an algorithm isn't available
 	 * @throws NoSuchProviderException
+	 *             if a provider isn't available
 	 * @throws NoOpenPgpKeyException
 	 *             if the file does not contain any OpenPGP key
 	 */
@@ -368,12 +370,17 @@ public class BouncyCastleGpgKeyLocator {
 	 * @throws IOException
 	 *             in case of issues reading key files
 	 * @throws NoSuchAlgorithmException
+	 *             algorithm is not available
 	 * @throws NoSuchProviderException
+	 *             provider is not available
 	 * @throws PGPException
 	 *             in case of issues finding a key, including no key found
 	 * @throws CanceledException
+	 *             operation was cancelled
 	 * @throws URISyntaxException
+	 *             URI is invalid
 	 * @throws UnsupportedCredentialItem
+	 *             credential item is not supported
 	 */
 	@NonNull
 	public BouncyCastleGpgKey findSecretKey() throws IOException,
@@ -543,10 +550,11 @@ public class BouncyCastleGpgKeyLocator {
 	/**
 	 * Return the first suitable key for signing in the key ring collection. For
 	 * this case we only expect there to be one key available for signing.
-	 * </p>
 	 *
 	 * @param signingkey
+	 *            the signing key
 	 * @param secringFile
+	 *            the secring file
 	 *
 	 * @return the first suitable PGP secret key found for signing
 	 * @throws IOException
diff --git a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgKeyPassphrasePrompt.java b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgKeyPassphrasePrompt.java
index 6144195983..463b661127 100644
--- a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgKeyPassphrasePrompt.java
+++ b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgKeyPassphrasePrompt.java
@@ -69,10 +69,13 @@ class BouncyCastleGpgKeyPassphrasePrompt implements AutoCloseable {
 	 *            the location the key was loaded from
 	 * @return the passphrase (maybe <code>null</code>)
 	 * @throws PGPException
+	 *             if a PGP problem occurred
 	 * @throws CanceledException
 	 *             in case passphrase was not entered by user
 	 * @throws URISyntaxException
+	 *             if the URI isn't parseable
 	 * @throws UnsupportedCredentialItem
+	 *             if a credential item isn't supported
 	 */
 	public char[] getPassphrase(byte[] keyFingerprint, Path keyLocation)
 			throws PGPException, CanceledException, UnsupportedCredentialItem,
diff --git a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/KeyGrip.java b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/KeyGrip.java
index c931724710..3eee18aef5 100644
--- a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/KeyGrip.java
+++ b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/KeyGrip.java
@@ -36,8 +36,8 @@ import org.eclipse.jgit.util.sha1.SHA1;
  * Utilities to compute the <em>keygrip</em> of a key. A keygrip is a SHA1 hash
  * over the public key parameters and is used internally by the gpg-agent to
  * find the secret key belonging to a public key: the secret key is stored in a
- * file under ~/.gnupg/private-keys-v1.d/ with a name "&lt;keygrip>.key". While
- * this storage organization is an implementation detail of GPG, the way
+ * file under ~/.gnupg/private-keys-v1.d/ with a name "&lt;keygrip&gt;.key".
+ * While this storage organization is an implementation detail of GPG, the way
  * keygrips are computed is not; they are computed by libgcrypt and their
  * definition is stable.
  */
diff --git a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/SExprParser.java b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/SExprParser.java
index a9bb22c780..c93c2164c9 100644
--- a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/SExprParser.java
+++ b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/SExprParser.java
@@ -95,7 +95,9 @@ public class SExprParser {
 	 *
 	 * @return a secret key object.
 	 * @throws IOException
+	 *             if an IO error occurred
 	 * @throws PGPException
+	 *             if some PGP error occurred
 	 */
 	public PGPSecretKey parseSecretKey(InputStream inputStream,
 			PBEProtectionRemoverFactory keyProtectionRemoverFactory,
@@ -252,7 +254,9 @@ public class SExprParser {
 	 *
 	 * @return a secret key object.
 	 * @throws IOException
+	 *             if an IO error occurred
 	 * @throws PGPException
+	 *             if a PGP error occurred
 	 */
 	public PGPSecretKey parseSecretKey(InputStream inputStream,
 			PBEProtectionRemoverFactory keyProtectionRemoverFactory,
diff --git a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/SecretKeys.java b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/SecretKeys.java
index 269a1ba0f6..a659d38fd3 100644
--- a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/SecretKeys.java
+++ b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/keys/SecretKeys.java
@@ -373,6 +373,7 @@ public final class SecretKeys {
 	 *            index of the closing quote in {@code in}
 	 * @return the dequoted raw string value
 	 * @throws StreamCorruptedException
+	 *             if object stream is corrupt
 	 */
 	private static byte[] dequote(byte[] in, int from, int to)
 			throws StreamCorruptedException {