Handle diff formatting when there is nothing to compare with

DiffFormatter now suports either side being null and the log program
will output the diff for the first commit.

Bug: 395791
Change-Id: I378957b57e9ad1f7195ba416f402178453f0ebd3

1 files changed, 78 insertions, 0 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffFormatterTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffFormatterTest.java
index 60b7460222..91498e7dfc 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffFormatterTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffFormatterTest.java
@@ -53,11 +53,13 @@ import org.eclipse.jgit.diff.DiffEntry.ChangeType;
 import org.eclipse.jgit.dircache.DirCacheIterator;
 import org.eclipse.jgit.junit.RepositoryTestCase;
 import org.eclipse.jgit.junit.TestRepository;
+import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.FileMode;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.patch.FileHeader;
 import org.eclipse.jgit.patch.HunkHeader;
+import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.treewalk.FileTreeIterator;
 import org.eclipse.jgit.treewalk.filter.PathFilter;
 import org.eclipse.jgit.util.FileUtils;
@@ -341,6 +343,82 @@ public class DiffFormatterTest extends RepositoryTestCase {
 		assertEquals(expected, actual);
 	}
 
+	@Test
+	public void testDiffRootNullToTree() throws Exception {
+		write(new File(db.getDirectory().getParent(), "test.txt"), "test");
+		File folder = new File(db.getDirectory().getParent(), "folder");
+		FileUtils.mkdir(folder);
+		write(new File(folder, "folder.txt"), "folder");
+		Git git = new Git(db);
+		git.add().addFilepattern(".").call();
+		RevCommit commit = git.commit().setMessage("Initial commit").call();
+		write(new File(folder, "folder.txt"), "folder change");
+
+		ByteArrayOutputStream os = new ByteArrayOutputStream();
+		DiffFormatter dfmt = new DiffFormatter(new SafeBufferedOutputStream(os));
+		dfmt.setRepository(db);
+		dfmt.setPathFilter(PathFilter.create("folder"));
+		dfmt.format(null, commit.getTree().getId());
+		dfmt.flush();
+
+		String actual = os.toString("UTF-8");
+		String expected = "diff --git a/folder/folder.txt b/folder/folder.txt\n"
+				+ "new file mode 100644\n"
+				+ "index 0000000..0119635\n"
+				+ "--- /dev/null\n"
+				+ "+++ b/folder/folder.txt\n"
+				+ "@@ -0,0 +1 @@\n"
+				+ "+folder\n"
+				+ "\\ No newline at end of file\n";
+
+		assertEquals(expected, actual);
+	}
+
+	@Test
+	public void testDiffRootTreeToNull() throws Exception {
+		write(new File(db.getDirectory().getParent(), "test.txt"), "test");
+		File folder = new File(db.getDirectory().getParent(), "folder");
+		FileUtils.mkdir(folder);
+		write(new File(folder, "folder.txt"), "folder");
+		Git git = new Git(db);
+		git.add().addFilepattern(".").call();
+		RevCommit commit = git.commit().setMessage("Initial commit").call();
+		write(new File(folder, "folder.txt"), "folder change");
+
+		ByteArrayOutputStream os = new ByteArrayOutputStream();
+		DiffFormatter dfmt = new DiffFormatter(new SafeBufferedOutputStream(os));
+		dfmt.setRepository(db);
+		dfmt.setPathFilter(PathFilter.create("folder"));
+		dfmt.format(commit.getTree().getId(), null);
+		dfmt.flush();
+
+		String actual = os.toString("UTF-8");
+		String expected = "diff --git a/folder/folder.txt b/folder/folder.txt\n"
+				+ "deleted file mode 100644\n"
+				+ "index 0119635..0000000\n"
+				+ "--- a/folder/folder.txt\n"
+				+ "+++ /dev/null\n"
+				+ "@@ -1 +0,0 @@\n"
+				+ "-folder\n"
+				+ "\\ No newline at end of file\n";
+
+		assertEquals(expected, actual);
+	}
+
+	@Test
+	public void testDiffNullToNull() throws Exception {
+		ByteArrayOutputStream os = new ByteArrayOutputStream();
+		DiffFormatter dfmt = new DiffFormatter(new SafeBufferedOutputStream(os));
+		dfmt.setRepository(db);
+		dfmt.format((AnyObjectId) null, null);
+		dfmt.flush();
+
+		String actual = os.toString("UTF-8");
+		String expected = "";
+
+		assertEquals(expected, actual);
+	}
+
 	private static String makeDiffHeader(String pathA, String pathB,
 			ObjectId aId,
 			ObjectId bId) {