Diff mode for Alpha.

Introduction

Basic usage

Examine the submenu Tools ↣ Compare. It contains items to compare windows, selections, files, or directories.
Use Compare ↣ Windows, Compare ↣ Selections, Compare ↣ FilesÉ, or Compare ↣ DirectoriesÉ to compare two things. When comparing windows, the two topmost windows will be compared, the topmost window being considered the old file. The Compare submenu is dynamical: holding down the Alt key (⌥) gives two new menu items: Compare ↣ Windows Word By Word and Compare ↣ Selections Word By Word, which give you more fine-grained differences and ignore changes which amount to differences in line breaking.
When a diff has been executed, a diff window is opened and a new Diff menu is inserted in the menu bar.
Use the Up and Down arrow keys to move around and compare the files.
Use the Control-Left and Control-Right key combos (⌃-Left and ⌃-Right) to patch changes from one window to the other.

Some example files are available: Click on this Compare Example hyperlink, which compares two versions of a .tcl file found in the Examples folder. Click on this CompareWordByWord Example hyperlink which compares two texts word by word.
Inspect the preferences Mode-diff preferences panel for various options that can be set to control the behavior of performing diff operations.

The diff mode resorts to a helper application to accomplish the actual comparison. This takes place in the background. In case of troubles, make sure your helper applications are configured correctly. To check or change the configuration select the AlphaCocoa ↣ Global Setup ↣ Helper Applications menu item and choose a "Diff" helper application.
See the Helper Applications preferences panel.
Alpha is distributed with a helper application called DiffBOA (Diff Background Only Application), which is located inside the Alpha bundle. A second option is to use diff which is just the unix diff tool, but beware that this implementation does not work on files with mac line-endings (CR). It support only the unix line-endings (LF). A third option is Built-in file comparison. That's Alpha's own pure-Tcl emulation of diff. It has two shortcomings: it does not diff folders, only files, and it doesn't respect any preference flags, always using linesOfContext equal to 0.

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