Add a "Content of selected file" entry to the copy menu for commit files

This is useful for copying the entire content of the selected file as it was at
the selected commit.

We only add it to the commit files panel; it is not needed in the files panel,
because there you can simply press "e" to edit the file.

pkg/gui/controllers/commits_files_controller.go

@@ -203,6 +203,16 @@ func (self *CommitFilesController) copyDiffToClipboard(path string, toastMessage
 	return nil
 }
 
+func (self *CommitFilesController) copyFileContentToClipboard(path string) error {
+	_, to := self.context().GetFromAndToForDiff()
+	cmdObj := self.c.Git().Commit.ShowFileContentCmdObj(to, path)
+	diff, err := cmdObj.RunWithOutput()
+	if err != nil {
+		return err
+	}
+	return self.c.OS().CopyToClipboard(diff)
+}
+
 func (self *CommitFilesController) openCopyMenu() error {
 	node := self.context().GetSelected()
 
@@ -246,6 +256,27 @@ func (self *CommitFilesController) openCopyMenu() error {
 		DisabledReason: self.require(self.itemsSelected())(),
 		Key:            'a',
 	}
+	copyFileContentItem := &types.MenuItem{
+		Label: self.c.Tr.CopyFileContent,
+		OnPress: func() error {
+			if err := self.copyFileContentToClipboard(node.GetPath()); err != nil {
+				return err
+			}
+			self.c.Toast(self.c.Tr.FileContentCopiedToast)
+			return nil
+		},
+		DisabledReason: self.require(self.singleItemSelected(
+			func(node *filetree.CommitFileNode) *types.DisabledReason {
+				if !node.IsFile() {
+					return &types.DisabledReason{
+						Text:             self.c.Tr.ErrCannotCopyContentOfDirectory,
+						ShowErrorInPanel: true,
+					}
+				}
+				return nil
+			}))(),
+		Key: 'c',
+	}
 
 	return self.c.Menu(types.CreateMenuOptions{
 		Title: self.c.Tr.CopyToClipboardMenu,
@@ -254,6 +285,7 @@ func (self *CommitFilesController) openCopyMenu() error {
 			copyPathItem,
 			copyFileDiffItem,
 			copyAllDiff,
+			copyFileContentItem,
 		},
 	})
 }