Doc: Describe changes in the diff editor

- Describe the context menu commands in the diff editor
  when used with Git
- Make the description of colors less specific, because they
  depend on the theme
- Use "chunk" consistently instead of "hunk"
- Update the screenshot

Change-Id: I6c9ec4eee8ff80f171558c930e5e448ac493f927
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

doc/qtcreator/src/editors/creator-diff-editor.qdoc

@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2018 The Qt Company Ltd.
+** Copyright (C) 2020 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the Qt Creator documentation.
@@ -80,11 +80,11 @@
 
     \image creator-diff-editor.png "Diff editor output in the Edit mode"
 
-    The changes are displayed in the \uicontrol Edit mode. Color coding is used
-    to mark changed lines. By default, light red indicates lines that contain
-    removed text (painted a darker red) in the left pane and light green
-    indicates lines that contain added text (painted a darker green) in the
-    right pane.
+    The changes are displayed in the \uicontrol Edit mode. Color coding is
+    used to mark changed lines. By default, red indicates lines that contain
+    removed text (painted another shade of red) in the left pane and green
+    indicates lines that contain added text (painted another shade of green)
+    in the right pane.
 
     To revert the changes, right-click added text and then select
     \uicontrol {Revert Chunk} in the context menu. To apply the changes, select

doc/qtcreator/src/vcs/creator-only/creator-vcs.qdoc

@@ -151,7 +151,8 @@
     instead, select the \uicontrol {Switch to Text Diff Editor} (1) option from
     the toolbar. In the inline
     diff view, you can use context menu commands to apply, revert, stage, and
-    unstage hunks, as well as send them to a code pasting service.
+    unstage chunks or selected lines, as well as send chunks to a code pasting
+    service.
 
     \section2 Viewing Versioning History and Change Details
 

doc/qtcreator/src/vcs/creator-vcs-git.qdoc

@@ -89,7 +89,8 @@
     by default. To use the unified diff view instead, select the
     \uicontrol {Switch to Unified Diff Editor} (1) option from the toolbar.
     In both views, you can use context menu commands to apply, revert, stage,
-    and unstage hunks, as well as send them to a code pasting service.
+    and unstage chunks or selected lines, as well as send chunks to a code
+    pasting service.
 
     \section2 Viewing Git Log
 
@@ -186,11 +187,18 @@
     When you have finished filling out the commit page information, click on
     \uicontrol Commit to start committing.
 
-    The \uicontrol {Diff Selected Files} button brings up a diff view of the
-    files selected in the file list. Since the commit page is just another
-    editor, you can go back to it by closing the diff view. You can also switch
-    to an open diff view by selecting it in the \uicontrol {Open Documents} view
-    in the sidebar.
+    The \uicontrol {Diff Selected Files} button opens a \l{Viewing Git Diff}
+    {diff view} of the files selected in the file list. Select
+    \uicontrol {Stage Chunk} in the context menu to stage a chunk or
+    \uicontrol {Stage Selection} to stage the selected lines.
+
+    To unstage chunks or selected lines, select \uicontrol {Unstage Chunk} or
+    \uicontrol {Unstage Selection} in the context menu. To revert the changes
+    in a chunk, select \uicontrol {Revert Chunk}.
+
+    The commit page is just another editor, and therefore you return to it when
+    you close the diff view. You can also switch to an open diff view by
+    selecting it in the \uicontrol {Open Documents} view in the sidebar.
 
     \section2 Amending Commits