ResolveMerger: Fix encoding with string; use bytes

This change fixes the issue [1]. Before this fix, a merge involving
the caching of consecutive yet similar filenames with Norwegian
characters [2] used to throw an IllegalStateException: Duplicate
stages not allowed. This was caused by inaccurate decoding of the
filenames, using string values assuming default encoding. In the
toString method of DirCacheEntry, used before through getPathString,
UTF-8 encoding is used, but the end result becomes default encoding,
through Object's default toString usage. The special characters in
those two consecutive (particular) filenames [2] were becoming the
very same decoded /single character, lending consecutive -but then
identical- filenames. Thus the perceived duplicate 0-staging of the
file(s).

Replace getPathString usage with getRawPath for this specific case,
or use byte array representations of cached entries instead of string.

Adding a test for this change is not possible, as there is no known
way to change the default encoding for filenames such as [2] (e.g.).
JGitTestUtil does write file contents through UTF-8, but encoding like
so does not apply to the actual file name. Hence there is no way to
create files with names properly made of special characters such as
[2]'s. And the test that is necessary for this case assumes such
Norwegian (or similar characters) filenames. Changing the default
locale programmatically in a test has no effect either. And changing
the LANG value passed to the JVM is only possible upon starting it.

[1] https://bugs.chromium.org/p/gerrit/issues/detail?id=9153

[2] <=>
(...)
"a/b/SíÒr-Norge.map",
"a/b/Sør-Norge.map",
(...)

Change-Id: Ib9f2f5297932337c9817064cc09d9f774dd168f4
Signed-off-by: Marco Miller <marco.miller@ericsson.com>

org.eclipse.jgit/src/org/eclipse/jgit/merge/ResolveMerger.java

@@ -393,7 +393,7 @@ public class ResolveMerger extends ThreeWayMerger {
 	 * @return the entry which was added to the index
 	 */
 	private DirCacheEntry keep(DirCacheEntry e) {
-		DirCacheEntry newEntry = new DirCacheEntry(e.getPathString(),
+		DirCacheEntry newEntry = new DirCacheEntry(e.getRawPath(),
 				e.getStage());
 		newEntry.setFileMode(e.getFileMode());
 		newEntry.setObjectId(e.getObjectId());