Add 'open file' command to context menu on diff tab

schema/plugin.json

@@ -172,6 +172,12 @@
           "label": "Git",
           "icon": "git"
         }
+      },
+      {
+        "type": "command",
+        "command": "git:open-file-from-diff",
+        "selector": ".jp-git-diff-title",
+        "rank": 1
       }
     ]
   }

src/commandsAndMenu.tsx

@@ -496,7 +496,7 @@ export function addCommands(
         getDiffProvider(fullPath) ?? (isText && createPlainTextDiff);
 
       if (buildDiffWidget) {
-        const id = `diff-${fullPath}-${model.reference.label}-${model.challenger.label}`;
+        const id = `git-diff-${fullPath}-${model.reference.label}-${model.challenger.label}`;
         const mainAreaItems = shell.widgets('main');
         let mainAreaItem = mainAreaItems.next();
         while (mainAreaItem) {
@@ -519,6 +519,7 @@ export function addCommands(
           diffWidget.title.caption = fullPath;
           diffWidget.title.icon = diffIcon;
           diffWidget.title.closable = true;
+          diffWidget.title.className = 'jp-git-diff-title';
           diffWidget.addClass('jp-git-diff-parent-widget');
 
           shell.add(diffWidget, 'main');
@@ -750,6 +751,55 @@ export function addCommands(
     icon: openIcon.bindprops({ stylesheet: 'menuItem' })
   });
 
+  commands.addCommand(ContextCommandIDs.openFileFromDiff, {
+    label: trans.__('Open File'),
+    caption: trans.__('Open file from its diff view'),
+    execute: async _ => {
+      const domNode = app.contextMenuHitTest((node: HTMLElement) => {
+        const nodeId = node.dataset.id;
+        return nodeId && nodeId.substring(0, 8) === 'git-diff';
+      });
+      if (!domNode) {
+        return;
+      }
+
+      const matches = toArray(shell.widgets('main')).filter(
+        widget => widget.id === domNode.dataset.id
+      );
+
+      if (matches.length === 0) {
+        return;
+      }
+
+      const diffModel = (
+        ((matches[0] as MainAreaWidget).content as Panel)
+          .widgets[0] as Git.Diff.IDiffWidget
+      ).model;
+
+      const filename = diffModel.filename;
+
+      if (
+        diffModel.reference.source === Git.Diff.SpecialRef.INDEX ||
+        diffModel.reference.source === Git.Diff.SpecialRef.WORKING ||
+        diffModel.challenger.source === Git.Diff.SpecialRef.INDEX ||
+        diffModel.challenger.source === Git.Diff.SpecialRef.WORKING
+      ) {
+        const file = gitModel.status.files.find(
+          fileStatus => fileStatus.from === filename
+        );
+        if (file) {
+          commands.execute(ContextCommandIDs.gitFileOpen, {
+            files: [file]
+          } as any);
+        }
+      } else {
+        commands.execute('docmanager:open', {
+          path: gitModel.getRelativeFilePath(filename)
+        });
+      }
+    }
+  });
+
   commands.addCommand(ContextCommandIDs.gitFileDiff, {
     label: trans.__('Diff'),
     caption: pluralizedContextLabel(

src/components/diff/NotebookDiff.ts

@@ -175,6 +175,13 @@ export class NotebookDiff extends Panel implements Git.Diff.IDiffWidget {
     return this._model.hasConflict;
   }
 
+  /**
+   * Diff model
+   */
+  get model(): Git.Diff.IModel {
+    return this._model;
+  }
+
   /**
    * Nbdime notebook widget.
    */

src/components/diff/PlainTextDiff.ts

@@ -80,6 +80,13 @@ export class PlainTextDiff extends Widget implements Git.Diff.IDiffWidget {
     return true;
   }
 
+  /**
+   * Diff model
+   */
+  get model(): Git.Diff.IModel {
+    return this._model;
+  }
+
   /**
    * Promise which fulfills when the widget is ready.
    */

src/tokens.ts

@@ -568,20 +568,24 @@ export namespace Git {
      */
     export interface IDiffWidget extends Widget {
       /**
-       * Refresh the diff widget
-       *
-       * Note: Update the content and recompute the diff
-       */
-      refresh(): Promise<void>;
-      /**
-       * Checks if the conflicted file has been resolved.
+       * Diff model
        */
-      isFileResolved: boolean;
+      readonly model: Git.Diff.IModel;
       /**
        * Gets the file model of a resolved merge conflict,
        * and rejects if unable to retrieve
        */
       getResolvedFile(): Promise<Partial<Contents.IModel>>;
+      /**
+       * Checks if the conflicted file has been resolved.
+       */
+      readonly isFileResolved: boolean;
+      /**
+       * Refresh the diff widget
+       *
+       * Note: Update the content and recompute the diff
+       */
+      refresh(): Promise<void>;
     }
 
     /**
@@ -1149,7 +1153,8 @@ export enum ContextCommandIDs {
   gitFileHistory = 'git:context-history',
   gitIgnore = 'git:context-ignore',
   gitIgnoreExtension = 'git:context-ignoreExtension',
-  gitNoAction = 'git:no-action'
+  gitNoAction = 'git:no-action',
+  openFileFromDiff = 'git:open-file-from-diff'
 }
 
 /**