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 *
 * @file svn_diff.h
 * @brief Contextual diffing.
 *
 * This is an internalized library for performing contextual diffs
 * between sources of data.
 *
 * @note This is different than Subversion's binary-diffing engine.
 * That API lives in @c svn_delta.h -- see the "text deltas" section.  A
 * "text delta" is way of representing precise binary diffs between
 * strings of data.  The Subversion client and server send text deltas
 * to one another during updates and commits.
 *
 * This API, however, is (or will be) used for performing *contextual*
 * merges between files in the working copy.  During an update or
 * merge, 3-way file merging is needed.  And 'svn diff' needs to show
 * the differences between 2 files.
 *
 * The nice thing about this API is that it's very general.  It
 * operates on any source of data (a "datasource") and calculates
 * contextual differences on "tokens" within the data.  In our
 * particular usage, the datasources are files and the tokens are
 * lines.  But the possibilities are endless.
 */