Update readme

readme.md

@@ -2,11 +2,27 @@
 
 Quickly browse through previous versions of a file.
 
-Usage: `gtm FILENAME`
+Basic usage: `gtm [filename]`
 
-Use the up/down arrow keys to browse through commits in the left pane, or to scroll the file in the right pane. Switch panes using the left/right arrow keys, or by clicking the mouse. You can also use h/j/k/l for navigation, and page up/down to scroll.
 
-Click and drag on the divider to resize the panes.
+## Options
+
+```
+-h, --help        show this help message and exit
+-d, --diff        Highlight newly added and deleted lines
+--diff-additions  Highlight newly added lines in green
+--diff-deletions  Show deleted lines in red
+--no-mouse        Disable mouse support
+-v, --version     Show version number
+```
+
+
+## Interface
+
+- use the up/down arrow keys (or h/l) to switch commits in the left pane, or scroll through the file in the right pane
+- use the left/right arrow keys (or j/k) to switch panes
+- use the mouse to select commits, switch panes, and resize the panes by dragging the divider
+
+- You can select text with the mouse, but you have to go a bit slowly. (Fixing that is on the TODO list.)
 
 ![screenshot](screenshot.png)
-