Log reason for ignoring pack when IOException occurred

This should help to identify the root cause of the problem discussed on
the Gerrit list [1].

[1] https://groups.google.com/forum/#!topic/repo-discuss/Qdmbl-YZ4NU

Change-Id: I871f70e4bb1227952e1544b789013583b14e2b96
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties

@@ -207,6 +207,7 @@ exceptionCaughtDuringExecutionOfRmCommand=Exception caught during execution of r
 exceptionCaughtDuringExecutionOfTagCommand=Exception caught during execution of tag command
 exceptionOccurredDuringAddingOfOptionToALogCommand=Exception occurred during adding of {0} as option to a Log command
 exceptionOccurredDuringReadingOfGIT_DIR=Exception occurred during reading of $GIT_DIR/{0}. {1}
+exceptionWhileReadingPack=ERROR: Exception caught while accessing pack file {0}, the pack file might be corrupt
 expectedACKNAKFoundEOF=Expected ACK/NAK, found EOF
 expectedACKNAKGot=Expected ACK/NAK, got: {0}
 expectedBooleanStringValue=Expected boolean string value

org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java

@@ -266,6 +266,7 @@ public class JGitText extends TranslationBundle {
 	/***/ public String exceptionCaughtDuringExecutionOfTagCommand;
 	/***/ public String exceptionOccurredDuringAddingOfOptionToALogCommand;
 	/***/ public String exceptionOccurredDuringReadingOfGIT_DIR;
+	/***/ public String exceptionWhileReadingPack;
 	/***/ public String expectedACKNAKFoundEOF;
 	/***/ public String expectedACKNAKGot;
 	/***/ public String expectedBooleanStringValue;

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ObjectDirectory.java

@@ -52,6 +52,8 @@ import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileReader;
 import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringWriter;
 import java.text.MessageFormat;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -329,7 +331,7 @@ public class ObjectDirectory extends FileObjectDatabase {
 					p.resolve(matches, id, RESOLVE_ABBREV_LIMIT);
 				} catch (IOException e) {
 					// Assume the pack is corrupted.
-					//
+					logCorruptPackError(e, p);
 					removePack(p);
 				}
 				if (matches.size() > RESOLVE_ABBREV_LIMIT)
@@ -418,6 +420,7 @@ public class ObjectDirectory extends FileObjectDatabase {
 							continue SEARCH;
 					} catch (IOException e) {
 						// Assume the pack is corrupted.
+						logCorruptPackError(e, p);
 						removePack(p);
 					}
 				}
@@ -499,6 +502,7 @@ public class ObjectDirectory extends FileObjectDatabase {
 							continue SEARCH;
 					} catch (IOException e) {
 						// Assume the pack is corrupted.
+						logCorruptPackError(e, p);
 						removePack(p);
 					}
 				}
@@ -541,7 +545,7 @@ public class ObjectDirectory extends FileObjectDatabase {
 					continue SEARCH;
 				} catch (IOException e) {
 					// Assume the pack is corrupted.
-					//
+					logCorruptPackError(e, p);
 					removePack(p);
 				}
 			}
@@ -552,6 +556,18 @@ public class ObjectDirectory extends FileObjectDatabase {
 			h.db.selectObjectRepresentation(packer, otp, curs);
 	}
 
+	private static void logCorruptPackError(IOException e, PackFile p) {
+		StringBuilder buf = new StringBuilder(MessageFormat.format(
+				JGitText.get().exceptionWhileReadingPack,
+				p.getPackFile().getAbsolutePath()));
+		StringWriter sw = new StringWriter();
+		e.printStackTrace(new PrintWriter(sw));
+		buf.append('\n');
+		buf.append(sw.toString());
+		// TODO instead of syserr we should use a logging framework
+		System.err.println(buf.toString());
+	}
+
 	@Override
 	InsertLooseObjectResult insertUnpackedObject(File tmp, ObjectId id,
 			boolean createDuplicate) throws IOException {