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Add sqlite3-diff: Display content differences between SQLite databases

sqldiff is a command-line utility program that displays content
differences between SQLite databases. The usual output is an SQL script
that will transform the source database into the destination database.

The sqldiff utility works by finding rows in the source and destination
that are logical "pairs". The default behavior is to treat two rows as
pairs if they are in tables with the same name and they have the same
rowid, or in the case of a WITHOUT ROWID table if they have the same
PRIMARY KEY. Any differences in the content of paired rows are output as
UPDATEs. Rows in the source database that could not be paired are output
as DELETEs. Rows in the destination database that could not be paired
are output as INSERTs.