Add download links to side-by-side viewer

Some users might want to download the new version of a single file,
so they can play with it locally, without actually patching the
entire change into a cloned repository.

Support that use case by offering our /cat/ servlet URL as a
"(Download)" link in the header of each file.

Bug: issue 416
Change-Id: Ie619207fe744824aed69603fe48d2a8520b9bd5d
Signed-off-by: Shawn O. Pearce <sop@google.com>
Reviewed-by: Nico Sallembien <nsallembien@google.com>

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchConstants.java

@@ -60,4 +60,5 @@ public interface PatchConstants extends Constants {
   String nextFileHelp();
 
   String reviewed();
+  String download();
 }

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/PatchConstants.properties

@@ -41,3 +41,4 @@ previousFileHelp = Previous file
 nextFileHelp = Next file
 
 reviewed = Reviewed
+download = (Download)

gerrit-gwtui/src/main/java/com/google/gerrit/client/patches/SideBySideTable.java

@@ -24,11 +24,14 @@ import com.google.gerrit.common.data.CommentDetail;
 import com.google.gerrit.common.data.EditList;
 import com.google.gerrit.common.data.PatchScript;
 import com.google.gerrit.common.data.SparseFileContent;
+import com.google.gerrit.reviewdb.Patch;
 import com.google.gerrit.reviewdb.PatchLineComment;
+import com.google.gwt.core.client.GWT;
 import com.google.gwt.user.client.ui.HTMLTable.CellFormatter;
 import com.google.gwtexpui.safehtml.client.PrettyFormatter;
 import com.google.gwtexpui.safehtml.client.SafeHtml;
 import com.google.gwtexpui.safehtml.client.SafeHtmlBuilder;
+import com.google.gwtorm.client.KeyUtil;
 
 import java.util.ArrayList;
 import java.util.Iterator;
@@ -73,7 +76,7 @@ public class SideBySideTable extends AbstractPatchContentTable {
     final SafeHtmlBuilder nc = new SafeHtmlBuilder();
 
     fmtB.setShowWhiteSpaceErrors(true);
-    appendHeader(nc);
+    appendHeader(script, nc);
     lines.add(null);
 
     int lastB = 0;
@@ -194,7 +197,7 @@ public class SideBySideTable extends AbstractPatchContentTable {
     return row;
   }
 
-  private void appendHeader(final SafeHtmlBuilder m) {
+  private void appendHeader(PatchScript script, final SafeHtmlBuilder m) {
     m.openTr();
 
     m.openTd();
@@ -211,6 +214,14 @@ public class SideBySideTable extends AbstractPatchContentTable {
     m.setStyleName(Gerrit.RESOURCES.css().fileColumnHeader());
     m.setAttribute("width", "50%");
     m.append(PatchUtil.C.patchHeaderOld());
+    m.br();
+    if (0 < script.getA().size()) {
+      if (idSideA == null) {
+        downloadLink(m, patchKey, "1");
+      } else {
+        downloadLink(m, new Patch.Key(idSideA, patchKey.get()), "0");
+      }
+    }
     m.closeTd();
 
     m.openTd();
@@ -222,11 +233,24 @@ public class SideBySideTable extends AbstractPatchContentTable {
     m.setStyleName(Gerrit.RESOURCES.css().fileColumnHeader());
     m.setAttribute("width", "50%");
     m.append(PatchUtil.C.patchHeaderNew());
+    m.br();
+    if (0 < script.getB().size()) {
+      downloadLink(m, new Patch.Key(idSideB, patchKey.get()), "0");
+    }
     m.closeTd();
 
     m.closeTr();
   }
 
+  private void downloadLink(final SafeHtmlBuilder m, final Patch.Key key,
+      final String side) {
+    final String base = GWT.getHostPageBaseURL() + "cat/";
+    m.openAnchor();
+    m.setAttribute("href", base + KeyUtil.encode(key.toString()) + "^" + side);
+    m.append(PatchUtil.C.download());
+    m.closeAnchor();
+  }
+
   private void appendSkipLine(final SafeHtmlBuilder m, final int skipCnt) {
     m.openTr();